Complex visualised flavour worlds - information from four domains presented simultaneously

Added on by Michael Bom Frost.

Edited for Nordic Food Lab’s blog by Michael Bom Frøst

Manuscript authors: Marta Bevilacqua, Barbara Santos Silva, Michael Bom Frøst, Benedict Reade, Kristen Rasmussen de Vasquez, Andra Tolbus, Mikael Agerlin Petersen, Rasmus Bro


Spice mixes are cornerstones of kitchens all over the world. The distinct flavours that is most often used in a cuisine are basic principles that determine that cuisine, so-called flavours principles (E Rozin & Rozin, 1981; Elizabeth Rozin, 1983). Some years ago we set out to characterise a good pool of 29 spice mixes of various origins –some classical ones from different parts of the world, some experimental ones that we ourselves at the lab had created and one that was donated to us from noma. The outcome of the sensory descriptions from 26 kind food professionals that donated their time and delicate palates to us is described previously in Calibrating Flavour part I. There are many pros and some cons of the sensory methods that we used (Frøst, Giacalone, & Rasmussen, 2015). It is very fast to duo, and can be carried out in almost any location that is relatively quiet and without too much sensory distraction such as smells and fragrances. On the other hand, the results will not be as precise as a traditional descriptive analysis carried out by a trained sensory panel. But for our purpose, to get an overview of the interrelations between a large group of spice mixes, it was precise enough. The results are extremely useful, and were created with a very small financial burden to us. 

But there was much more to this audacious adventure. At University of Copenhagen’s Department of Food Science, the spice mixes were analysed by Headspace Gas Chromatography under conditions that simulate the conditions during eating a food, where the aromatic volatiles of the food enter the nose via the back of the throat (the retronasal pathway, (Shepherd, 2006)). Further, the aroma molecules were identified by mass spectroscopy (so-called GC-MS, Hübschmann, 2015).

The purpose of this was to study and visualise information of very different origins, but all characterising the same 29 spice mixes. There are 4 types of information that we can link:

  1. The sensory map (Map) – Using projective mapping to characterize the samples. These measurements are collected in a matrix of dimension 29 rows x 52 columns (26 evaluators x 2 coordinate axes).
  2. Sensory descriptors (Words) - In addition to the positions from the projective mapping, there are also a number of words that the sensory respondents (the food professionals) have attached to the spice mixes. After some textual analysis of the original set of words (totalling 545 different words), this set of data consists of a matrix with 29 rows and 113 columns – 113 different and relevant words that escribe the sensations of the spice mixes.
  3. Aroma profiling (Odour chemicals) - Through headspace sampling, GC-MS analysis was used to obtain an aroma profile for each spice mix. The aroma profile consisted of the relative integrated peak area (relative concentration) of 122 different odorous compounds. Some of the compounds have available sensory descriptors, collected in a smaller matrix (29 x 25 named Odour descriptors).
  4. Meta-data – name (Recipe), expressed solely as the fraction of each ingredient, the cultural identity or origin (geographical place or producer) and the base (oil, aqueous, dry, fermented and dairy). A matrix of 29 x 99 variables.

The data blocks are presented in figure 1. 

Figure 1: Overview of all data blocks available

By developing new visualization approaches and using tools from data fusion, we analysed, visualised, and explored these complex data structures. We used these tools to investigate the fundamental differences and commonalities in the set of spice mixes.  It is a work of very interdisciplinary nature, requiring data analysists, flavour chemists, food professionals and sensory scientists. The process was a feast for geeks, with wild and imaginative discussions, bouncing ideas and swimming in the data. However, the harsh realities hid us hard when submitting the manuscript to scientific journals. Because of the interdisciplinary nature, it was difficult for others to appreciate all aspects of the work, and we had it turned down from four different journals. Finally we had to realise that the ideas and results we presented to the scientific community would not be published in peer-reviewed scientific journals. With this blog post we present you the idea and the concept, and the opportunity to delve deeply into our investigation by reading the full manuscript here, where all details about the chemical and data analytical procedures are available, and the results are discussed in details. In addition, we find that the data are of a unique character. Thus we give access to the data, so that others may use them for further scrutiny. The data can be found here.

Excerpts of results

The projective mapping and the aroma profiling by GC-MS provide two complementary means to quantify the differences between spice mixes, and can be used to perform a combined analysis that shows to what extent sensory results are already contained in the aroma analysis and vice versa. The full data are very complex to present visually, and a low-rank sub-space of the total variation is obtained by multivariate data analysis, Principal Component Analysis (PCA) to be precise. PCA extracts the most important variance in the data, component by component. It allows focus on the most important part of the variance, in the analysis of the patterns of samples and the variables that describe them.

In figure 2, the first two and most important components of the PCA model are shown. These components explain 50% of the variability of the data. In particular, the score plot with all of the samples colored by origin (geographical or developed by), are plotted on the top left corner of the figure (Plot A). Plot B shows the words that the evaluators have used for describing the same samples. Plot C shows a loading plot of the volatile odour compounds. Finally, the recipe plot (Plot D) shows how the mixes can be interpreted on the basis of their ingredients. There is a robust relationship across all the matrices, demonstrating that the different matrices extract similar patterns about the spice mixes.


Figure 2A: Visual representation of the most important variance in the four data blocks
Sensory map and Sample origin group designated by simlar symbols (origins: Africa;  Asia;  Britain;  Central America;  Nordic Food Lab or noma  Scandinavia;  South America;  Southern Europe).  See more in full manuscript.

Figure 2B Sensory Words. The descriptors used by the panel to characterise the sensory properties of the spice mixes.

Figure 2C: Odour chemicals and descriptors: The different odorous compounds, and in some cases the sensory descriptors that are known to be associated with the compounds.

Figure 2D: Recipes: Expressed as the fraction of each ingredient, the cultural identity or origin (geographical place or producer) and the base (oil, aqueous, dry, fermented and dairy).

The aroma analysis using gas chromatography (Figure 2 plot C), allows us to dig further into the data. Observation of plot C shows a loading plot of the volatile odour compounds. On the same plot on top of the odour chemicals, the odour descriptors are shown. The plot shows how most of the odours are gathered in the upper-right part of the plot. This can be interpreted as a general trend of increased intensity of aroma, going from the samples in the bottom-left part of the scores plot towards those in the upper-right part. The dry base consists mainly of mixes of pure spices that have been ground up, which contain a high concentration of many highly volatile compounds, e.g. terpenes. The fermented mixes will undoubtedly have a considerable content of acids and umami compounds which are not captured by the GC analysis, but will contribute to the taste of the mixes. The oil-based mixes appear to contain a medium level of aroma compounds, but this may be due to higher aroma retention in the oil under the conditions for trapping the aroma compounds.  Finally, the recipe plot (Figure 2, plot C) shows how the paste grouping can be interpreted on the basis of their ingredients. One can see how the ingredients naturally reflect the groupings such as blueberry in the left part, juniper in the upper, and chipotle in the lower part. A very detailed analysis of the patterns is provided in the full manuscript.

It is a comprehensive way to fuse sensory projective mapping data, gastronomic information (recipes), and aroma profiling (gas chromatographic data). The method also allows for inclusion of additional data if available. More efforts are needed to help minimize the barriers that result from this highly cross-disciplinary experiment. There is a need for the ability to communicate across many fields of expertise such as chemistry, flavour research, gastronomy, mathematics, and sensory science. Finding a common language that allows open and creative communication is of paramount importance for the advancement of the field.

We made a large effort to improve the visualization of the problem by enhancing the readability of the most important loadings in all the loadings plots. However, work is still required and in the future we intend to expand on this, taking advantage of modern tools that computer science offers, such as interactive visualizations that allow a deeper exploration of complex data for which static plots are sometimes inadequate.

Acknowledgements and thanks
We kindly acknowledge the 26 persons that gave their valuable time to evaluate the spice mixes. In addition, we acknowledge noma for the donation of Ants and juniper mix. We acknowledge Kiki Sontiyart, Ana Caballero and Guillemette Barthouil for their contribution to the creation of the spice mixes. And lastly we thank the anonymous reviewers that helped us improve the manuscripts along the way.


Acar, E., Rasmussen, M. A., Savorani, F., Næs, T., & Bro, R. (2013). Understanding data fusion within the framework of coupled matrix and tensor factorizations. Chemometrics and Intelligent Laboratory Systems, 129, 53–63.

Frøst, M. B., Giacalone, D., & Rasmussen, K. K. (2015). Alternative methods of sensory testing: Working with chefs, culinary professionals and brew masters. Rapid Sensory Profiling Techniques and Related Methods: Applications in New Product Development and Consumer Research.

Hübschmann, H.-J. (2015). Handbook of GC/MS: Fundamentals and Applications (3rd ed.). Wiley & Sons.

Rozin, E. (1983). Ethnic Cuisine: The Flavor-Principle Cookbook. Brattleboro: The Steven Green Press.

Rozin, E., & Rozin, P. (1981). Culinary themes and variations. Natural History, 90, 6–14.

Shepherd, G. M. (2006). Smell images and the flavour system in the human brain. Nature, 444(7117), 316–321.

Making Tea Edible: Laphet from local plants in three ways

Added on by Michael Bom Frost.

by Liis Tuulberg

Laphet made from young birch leaves, fermented with whey from acidified milk (syrnet mælk)

Laphet made from young birch leaves, fermented with whey from acidified milk (syrnet mælk)

Burmese people do not only drink a lot of tea, but also eat it. Laphet (also lahpet, lephet, letpet, leppet) in Burmese represents a generic term for fermented pickled tea leaf, whereas laphet thoke/thohk, fermented tea leaf salad, and ahlu-laphet, a laphet snack, are the most common ways to consume laphet (Maung, He and Chamba 2012). Laphet carries a lot of cultural and historical significance in Burma, it is associated with national pride and considered to be a national dish. It is claimed that in ancient times laphet was used as a peace offering or peace symbol between kingdoms at war. In present day Burma, laphet is a habitual dish eaten in various social settings by all Burmese — from traditional ceremonies, monasteries and official celebrations to homes and family get-togethers. It is said that through a laphet tray one demonstrates his/her hospitality towards houseguests (Han and Aye 2015). Burmese also believe laphet to hold health benefits, calling it “Lord leaves” and “Lord Medicine” (Maung et al. 2012). Since it is a staple food, laphet products are found all over Burma; the street stalls in Burmese cities selling plates of laphet thoke are the common manifestations of this food culture (Han and Aye 2015).

With an urge to broaden the knowledge around edible plants and to take up the fermentation of tree and bush leaves in the Lab, in the spring of 2016 I embarked upon an endeavour to replicate laphet using local leaves. At first I chose in-season leaves similar to the tea plant camellia sinensis, with a high quantity of tannins. Over the progression of spring, my local laphet leaf candidates started to successively develop into the right picking condition. Specifically, my intention was to use younger leaves that were large enough to comfortably work with but not yet too fibrous and firm. And so, in three successive weeks, I undertook three foraging trips. Together with Michael I foraged beech leaves from the Ganløse Ore forest, in Værløse, I picked black currant leaves from a farm in Lejre near Roskilde and finally I collected birch leaves from the luscious Amager fælled in Copenhagen together with a fellow intern. Hence, the leaves for my laphet experiment came from very different sources. These leaves held the stories of the places and people from which they came.

The process of making laphet

Laphet is produced by anaerobically fermenting tea leaves, resembling the production process of Japanese post-fermented teas awa bancha and goishicha (Shii et al. 2014). The preparation of laphet starts with harvesting and selecting young tea leaves to undergo fermentation. The oxidation of the fresh leaves is stopped by steaming them for approximately five minutes, then water is removed and another selection process occurs. Leaves are then packed into clay pots and pressed with heavy weights to encourage fermentation. At certain intervals, leaves are checked and some additional steaming can be applied. Steaming increases the production of phenolic compounds found in the tea leaf, which, in turn, enable the growth of particular microbes, whereas other unwanted and detrimental microbes are unable to grow even if fermentation is carried out in non-sterile conditions (Han 2015). According to some accounts, rolling the leaves takes place in-between the steaming and pressing stages (Maung et al. 2012). The fermentation takes place due to the naturally occurring lactic acid bacteria (LAB) present on the leaves and in the environment. Some reports claim laphet is fermented in bamboo vats (rather than clay pots) that are placed in pits in the ground (Zafrudin 2010) — this process adds an interesting layer to the fermentation in regards to environment and temperature change.

The laphet pulp softens in a few weeks, though there are different accounts of when the fermentation process is complete — from two weeks to three to four months up to a year (Han 2015; Maung et al. 2012; Zafrudin 2010). However, there are certain physical characteristics that imply when the fermentation is ready - leaves start to soften and change colour from green to golden green and the acidity decreases (Han 2015). It seems to me that the aim of the fermentation is not so much to preserve the leaves, though the fermentation process surely enables one to consume the tea leaves over a longer time span. But fermentation is foremost carried out to break down the fibrous structure and to attenuate the bitter taste of fresh tea leaves, while simultaneously adding some interesting flavour and aroma characteristics. In some sense, leaves are made more edible through the fermentation process.

When I designed my laphet experiment, I had to consider that the conditions for processing laphet in Denmark are rather different from those in Burma. Much to my sorrow, the lab context did not really allow me to ferment the laphet in bamboo vats in the ground up to a year… Also, I could not be certain if wild fermentation would start based on the LAB found naturally on the leaves, as it does with the original laphet. I needed to be sure that it is the LAB fermenting the laphet and that some other bacteria will not take over. Therefore, I decided to inoculate the leaves with various sources of LAB, creating five different versions of laphet in each batch. For the different sources of LAB, I used whey strained from syrnet mælk (A) and yogurt (B) as well as some skyrkultur (C) and fermented bee pollen (D) that I mixed with filtered tap water. In addition, I also immersed the leaves in salt brine (E) to create an environment favourable for the LAB. Because the beech leaves gave out enough liquid, I was able to immerse the leaves in their own liquid and thus create a wild fermentation, similarly to the original laphet. The currant and birch leaves were too dry for the same process.

Before the inoculation, I followed a similar procedure with all three batches. I briefly steamed the fresh leaves - thirty seconds for more tender beech leaves, two minutes for more fibrous currant and birch leaves, I then rolled and massaged the wilted leaves and mixed with the different sources of LAB. At that point, I placed the leaves into glass containers and submerged them under the liquid with weights. I checked the progress from time to time, and let the leaves ferment for at least two weeks.


The bright green fresh beech leaves seemed promising — texturally tender and light, yet somehow resilient; taste-wise pleasantly astringent, resembling unripe persimmon. From the three leaf candidates, they were most similar to the leaves of camellia sinensis. During fermentation, rather strong perfume-like sour and sweet aromas started to develop, with some batches producing some tainted smells as well. In two weeks, the flavours that had generated were mostly strongly acidic and wine-like sweet-sour flavours, sadly the texture that turned out to be unpleasant. Contrary to my hopes of a soft and delicate composition, the tender leaves had dissolved into a puree-like mass, though an unpleasant toughness still remained when trying to chew the leaves. It was clear that consuming beech leaves in a traditional way (such as mixed in a salad) would not work, so I decided to experiment with a different approach. I took the beech leaves that I had fermented in salt brine, I rinsed them to remove a bit of the saltiness and pounded the leaves into a paste together with some typical Burmese flavours such as fresh ginger, fresh garlic, and chilli, while also adding some oil, soya and rice vinegar to enhance the texture and flavour. It turned out to be a potent sour-spicy paste that could be served as a condiment to grains and certain vegetables. Perhaps a more mildly flavoured sour paste from the fermented beech leaves would work as a condiment for fresh cheeses like burrata. Still it must be pointed out that the leaves which at first seemed most promising, actually turned out to be the least interesting in terms of flavour and most problematic in terms of texture.

Black currant

Compared to the beech leaves, fresh black currant leaves had a tougher texture, were more fibrous and rather dry. They released little moisture even after steaming and rolling. Their aroma was straightforward of black currants, even more so after steaming. Though by the fifth fermentation day, the black currant aroma was replaced with cloying or in some cases more complex sweet-sour smells. Two weeks after the start of fermentation, a mellow and more complex currant-like character returned with some other intriguing aroma and taste advancements. In fact, how the collected leaves reacted to the different LAB sources and made the flavours and smells of the leaves transform during the fermentation, was beautifully demonstrated with the black currant leaves laphet batch.

Consider the black currant leaves fermented in syrnet mælk whey. After two weeks, the flavour could be characterised as fruity and sour in the beginning and metallic towards the end, resembling green unripe strawberries or juicy green peaches. The aroma, in turn, elicited savoury vegetable notes, reminiscent of green chilli peppers. Moreover, the fibrous texture of the currant leaves had remained but also transformed into a state where the leaves were simultaneously firm and half-way soft, thus pleasant to chew and fitting well to be incorporated into a simple fresh salad. The currant leaves fermented with yoghurt whey had a pleasant fibrous and dense texture, encouraging the eater to work with her or his teeth, or, ‘get back the bite’ as one taster fittingly commented. The same person also reported an experience of a long progression of tastes with this laphet version - from bright sour to tingling sensations to metallic and mineral notes, overall reminding him of the experience of eating grape leaves.

There was one more black currant laphet version — black currant leaves inoculated with fermented bee pollen where the flavour profile showed good potential, with notes of apricot, melon, capers and cucumbers. However, the texture of the leaves maintained a disturbing fibrousness. For this, an idea was born to develop the texture further. I detangled and dehydrated the leaves overnight. The result was sour and tender black currant leaf chips, extremely crunchy and subsequently melting in the mouth. Contrary to the freshly fermented leaves, where the acid came right at the beginning and then softened in complex ways, the dried leaves had almost the opposite effect — first you got the texture, it then disintegrated a little bit on the tongue and then a delayed flavour burst followed.

These acidified dried black currant leaves were ideal to use in a Nordic furikake. Furikake is a dry Japanese seasoning consisting typically of chopped dry seaweed, sesame seeds, dried and ground fish and some salt and sugar. It is usually sprinkled over cooked rice, vegetables and fish. At the Lab we mixed the laphet leaves with some dried and grated deer leg for umami taste and some buttered buckwheat grains for texture, while also adding a bit of salt. The Nordic furikake turned out to be a delicious condiment to be sprinkled on top of rice or local fresh potatoes.

Dehydrating fermented black currant leaves 

Dehydrating fermented black currant leaves 

New potatoes in a Nordic furikake made from dried black currant laphet leaves and buttered buckwheat

New potatoes in a Nordic furikake made from dried black currant laphet leaves and buttered buckwheat

The black currant leaves that I had fermented in salt brine also responded well to dehydration, changing into salty-sour leafy and crunchy chips. While still preserving their leafy and woody character, they were enhanced by drying, evoking associations from commentators such as ‘a leaf that might have been sitting on top of a cheese’, referring to the umami taste the leaf acquires when wrapped around some flavourful cheese.

Salty-sour and umami-rich dried black currant leaves on cheese

Salty-sour and umami-rich dried black currant leaves on cheese

The conclusion from the tastings is that the black currant leaves which seemed rather one-dimensional while fresh, transformed after fermentation into a complex mixture of flavours, tastes and textures, with options to choose between different courses of action when processing to optimise them for different gastronomic purposes.


Fresh birch leaves were light and soft, though it is important to emphasise that I picked spring leaves that, although fully developed in size, were still young and tender. Birch leaves, similarly to currant leaves, were also rather dry and somewhat fibrous (especially compared to the beech leaves). Though in most birch laphet versions, the fibrousness of the birch leaves disappeared during the fermentation and a firm leafy texture remained, enabling a soft, yielding and pleasant bite. The bitter taste of fresh birch leaves faded as a consequence of the fermentation, making the birch leaves great candidates for salads replicating original laphet consumption. Although there were also some birch trials (e.g. birch leaves with salt brine) that elicited some peculiar sensations, such as foamy and soapy sensations in the mouth as well as associations to licking a battery – the sensation of low-current electricity, or from gastronomic origin, that of Sichuan pepper (seeds from threes of  Zanthoxylum genus). Birch leaves fermented with bee pollen even evoked feelings of pain in the sides of the mouth of one taster; he associated it with strong fermented foods that make him feel agitated, excited and hot.

The best among the birch laphet batches were definitely birch leaves fermented in whey from syrnet mælk. These leaves were beautifully balanced, ticking the acidity, texture, aroma and fruitiness boxes. The texture was slightly slippery yet still with a good bite; the taste was fruity – reminiscent of sour cherries. I used these birch leaves to make our own version of the laphet thoke, the traditional Burmese tea leaf salad. Laphet thoke is a balancing act of tastes and textures, interweaving earthy, tart and spicy taste notes together with chewy, soft and crispy textures. This is what I aimed to achieve when mixing the pungent leaves together with some roasted garlic slices, pickled ginger stripes, sliced broccoli stems, boiled chickpeas, sesame seeds and fermented green chillies, while flavouring the salad mixture with fish sauce, lime juice and sesame oil.

Laphet thoke

Laphet thoke

On Eating Insects – Essays, stories and recipes

Added on by Michael Bom Frost.

New book by Nordic Food Lab - Available for pre-order now

On Eating Insects – Essays, stories and recipes. A book by Nordic Food Lab published by Phaidon available for pre–order now.

On Eating Insects – Essays, stories and recipes. A book by Nordic Food Lab published by Phaidon available for pre–order now.

Insects have been the center of many of our activities during the last years. In May 2016 we finished the Velux-funded project ‘Deliciousness of insects’, and naturally there has been many outcomes from that in the recent year - talks, press, publications, and very importantly a feature length-documentary film BUGS by Andreas Johnsen.

The last milestone we lay down for the project is the publication of a book. On eating Insects – Essays. Stories and recipes. The book is published by Phaidon, and it will be out in bookstores May 1st. It can be pre-ordered from the publisher through this link, or from major retailers. We list Nordic Food Lab as author, as we find that first and foremost this book is a result of the lab's work. We know that this is not the conventional way of authorship. The authors from the lab are Josh Evans, Roberto Flore and Michael Bom Frøst. Many other people contributed to the project and we are genuinely thankful for their work. This brief blogpost is not the right place to list all of them - they are mentioned in the book. But in particular we need to thank Chris Tønnesen for the beautiful images, Rene Redzepi and Mark Bomford of Yale's Sustainable Food Program for writing foreword and introduction. Lastly we thank our editors at Phaidon, Sophe Hodgkin and Ellie Smith. 

We really look forward to bring this book to the world.

The end of the project also meant that Josh moved on from the lab after being four years with us. We wish him all the best with his future studies at University of Cambridge.

The Nordic Food Lab will continue to investigate the gastronomic potential of insects in the coming years. Michael and Roberto will be involved in a new large insect project - InValuable - with many partners in Denmark and abroad. Here our role is smaller but as essential – the creation of delicious insect foods.

A double farewell

Added on by Michael Bom Frost.

Today is Jonas and Josh's last day at the lab.

Jonas started helping out at the lab informally back in 2010, and while he was completing his master's studies he did his project-in-practice on kombucha and a bee larvae consumer acceptance study for his thesis. He joined the lab as staff in July 2014 to head up our contributions to the Smag for Livet project; now, he'll be working with the Meyer group on product development.

Josh came to the lab as an intern in June of 2012, and was hired one year later when we gained three years of funding for our insect research. This project is just wrapping up, and while we will continue to work with insects, Josh will be moving on to begin post-graduate study in England in the fall.

We thank both for their multiple contributions to our work, and we wish them all the best for their future investigations, and much continued deliciousness.

BUGS Premiere

Added on by Josh Evans.

Last week, our documentary film BUGS, directed by Andreas Johnsen, had its world premiere at the Tribeca Film Festival in New York.

There were four screenings, some great Q&A sessions, many press interviews, and two pop-ups—the first with escamol ice cream served on the High Line, the other with escamol tacos served at Miscelanea, a self-described Mexican general store in the East Village. Both were made possible by José Carlos Redon and his brother Alessandro, who helped us out with our fieldwork in Mexico in March 2014 and flew up to NYC for the premiere—with 10kg of escamoles no less!

Many thanks to Andreas, Peter, and everyone at Danish Documentary for making it a thrilling and successful week.

The film will be having other continental and national premieres over the coming months, so stay tuned for news here and over on, the website for the film. Until then, here is the official trailer.

Tea but not

Added on by Josh Evans.

by Josh Evans

I like tea. I like how one plant becomes many different kinds of drink. I like that one can cultivate the craft of brewing it, as well as just enjoy it simply. I like that it has rituals, and its psychotropic effects. I like that lots of other people like it, but not everyone likes it the same way.

This is a 3-years-long story about tea and tea-like non-teas. But it didn't start with tea. It started—as more than a few of our projects do, it seems—with a fungus.


Part 1—A. niger and Pu-erh

Meet Aspergillus niger. Yes, it is part of the same genus as our homeboy A. oryzae. But the similarities largely stop there. While the koji mould is white, for example, this one, as its name suggests, is black. And while koji mould is used for making all sorts of fermented products like miso, soy sauce, sake, amazake, shio-koji, and others, A. niger occupies a very different edible niche. In many cases, actually, A. niger is seen as an agricultural pest. It's quite ubiquitous across all sorts of soil samples. Yet for a certain type of tea called Pu-erh, produced in Yunnan province in the south of China, A. niger is one of the process' key microorganisms.

Most teas, it turns out, are not strictly speaking 'fermented'—that is, their transformations are not the result of microbial metabolism, but rather variations of oxidation, autonomic or enzymatically facilitated, modulated by physical techniques of wilting, steaming, panning, baking, rolling, drying and others in a great many combinations.

A flowchart of tea processing that simplifies a much more complex combinatorial range of methods. (Wikipedia)

A flowchart of tea processing that simplifies a much more complex combinatorial range of methods. (Wikipedia)

That's where the Pu-erh comes in. This tea does involve microbial metabolism—after undergoing some of the first steps that usually lead to green tea, the partly-processed leaves are heaped into piles and let to spontaneously ferment. A. niger comes to dominate and contributes prominently to its flavour, adding notes of earth, moss, and cellar to the mix (geosmin is one of its main secondary
metabolites), while rounding astringency and smoothing bitterness. It brings a particular perspective to an already complex product—the result is something that, unlike many teas which begin to deteriorate as soon as their processing is complete, can be aged for ten, twenty, thirty years or more, increasing in complexity and nuance, and demanding even more when it comes to brewing and drinking it best. More like a wine than an olive oil. A pu-erh-obsessed friend of mine in Japan, Max McCurdy, brewed us some while I was in Tokyo in November 2014, after our insect field work. He had a tiny teapot, one that could fit into the palm of my hand; we only started drinking from the third brewing, and kept drinking until well after the tenth. It is, in my experience, a particularly convivial way of drinking tea, as it demands repeated motions of boiling, brewing, and pouring that become perfect punctuations in a long, slow-burning series of shared caffeinated jaunts.

Max's tiny pu-erh pot being drained for drinking

Max's tiny pu-erh pot being drained for drinking

January 2013 is when I first started looking into microbial action in tea. Mycotoxicity in many fungal species can vary according to the strain and growth conditions, but with a bit of research I learned that A. niger is generally safe for human consumption (Blumenthal, 2004). I first met A. niger in person in February, after our friend and fellow fungal enthusiast Sara Landvik, a researcher at Novozymes, graciously agreed to plate me a couple known strains from their open collection. I propagated them on some standard PDA plates we had already prepared (petri dishes with a simple mixture of potato starch and dextrose in an agar gel), and planned the plants I would try to encourage the fungus to ferment into some sort of pu-erh-like tea.

Here are my notes from trials over the 2013 growing season.

I began with A. niger plated up by Sara Landvik, our friendly microbiologist at Novozymes, replated it to multiple plates, let it sporulate, then mixed the spores into sterilized water, and steeped dried verbena leaves in a small amount of liquid inoculum to coat and absorb. 
They are now slowly drying. 

Lemon verbena pu-erh

Lemon verbena pu-erh

The verbena pu-erh has been sitting for months and is still very fragrant - earthy and complex.
Now we are in the season of growth. I have begun trials with elderflower, jasmine, nettles, beach rose (pink and white), dittander (leaves and flowers). Going to look for fireweed (
Chamerion angustifolium) - similarities to Camellia sinensis.
I've put the A. niger inoculum into an atomiser.

Elderflower (Sambucus nigra)

Elderflower (Sambucus nigra)

Elderflower - I sprayed some whole on the stem and also loose, and left it out at room temperature on a plate. I also blanched a few heads then inoculated and left them out. The blanched ones have turned a dark green with black tips and a stronger smell - the rupturing of the cells seems to enhance the enculturation, even beyond the oxidation.



Jasmine - I harvested some jasmine from the tree at my house. Should figure out which species it is. Now with the more delicate flowers I have started using the vacuum packer to vacuum impregnate the cells with the liquid inoculum, instead of blanching. It also helps speed oxidation. After three days of drying the vacuum-impregnated flowers are noticeably darker and more aromatic.

The compressed jasmine (L) became slightly darker and gained a deeper, smokier smell than the uncompressed (R).

The compressed jasmine (L) became slightly darker and gained a deeper, smokier smell than the uncompressed (R).

Nettles - I rinsed dry whole nettle leaves in water to soften, then tossed them gently with the liquid inoculum.

Nettles (Urtica dioica)

Nettles (Urtica dioica)

Beach rose (Rosa rugosa)

Beach rose (Rosa rugosa)

Beach rose - Pink and white. I separated loose petals and whole blossoms, and again did half just spray and half sprayed then vacuum impregnation. Not so much difference here yet but we will see.

Justine with flowering dittander (Lepidium latifolium)

Justine with flowering dittander (Lepidium latifolium)

Dittander - the leaves and flowers are still drying - they are quite sturdy, perhaps too much so for this processing. The flowers smell mainly of hay. The leaves look somewhat promising - but next time I should rub them between my hands more vigorously to get the oxidation going, before continuing the process.

Processing the dittander

Processing the dittander

Dittander flowers and leaves

Dittander flowers and leaves

The flowers are becoming more fragrant.
The dittander doesn't oxidise fully when bruised. It ends up just losing most of its pungency and drying out.
The nettles are promising - they oxidise very well, and gain fantastic aroma.

Finished nettle tea.

Finished nettle tea.

Justine found fireweed in Charlottenlund on Tuesday 23.7. I stripped the leaves that evening, rolled and pressed them to break the cells and begin the oxidation. I kept them in a plastic container until Thursday evening. They generated humidity and began smelling strongly: overripe mango, feijoa, curing apple, bubblegum, terpinic, guava, green, juicy fruit apple, hay, grass, summer, benzyl anthranilate (grapefruity/tropical flavours). Thursday evening I spread them out to dry and continue oxidising on the counter. 
Friday morning I sealed them in vacuum bags to ferment anaerobically over the weekend.
The half kept in the box retained its fruity, berry aroma, while the one left to dry open had these fruity notes replaced with more green, fresh hay, green banana.

Both bags when opened smell strongly of olives and pickles - very lactic and savoury. This mellows quite quickly.
I split each batch (aired/sealed) into two, toasted half in a pan until just before crisp and the other steamed in the oven, both to halt the fermentation.
The toasted ones smell like: 'roasted pineapple' (Sarah), 'herbaceous and green' (Avery), 'vinegar sauce' (Justine), 'sexy'/'arousing' (Ben)
The steamed ones smell like: 'banana' (Sarah), 'olives'/'some sort of piss' (Justine), 'capers'/'marine'/'piss' (Ben)
The dittander has since turned into vomit; they can be forgotten.

Finally a sensory.
First the flowers - beach roses (white and pink), and jasmine. 1.2g/120ml water (80˚C), 4 min infusion. The roses are both weak and insipid, but the jasmine has potential - smells of old leather, smoke, old perfume. It is grown-up. A stronger extraction could help, and perhaps a tincture.

Lemon verbena was also worthwhile—its aromatic top notes became subdued and gained a grown-up richness not usually present in the herb, fresh or dried.

Lemon verbena was also worthwhile—its aromatic top notes became subdued and gained a grown-up richness not usually present in the herb, fresh or dried.

Next, the original lemon verbena. 2.4g/120ml water (80˚), 4 min. infusion. Multiple infusions as follows:
1st. Musty, woody, mouldy. It smells rounded, the similar sensation of smelling cold cream. The taste is unbalanced and fuzzy, not unpleasant but neither so pleasant.
2nd. It is stronger - leather, cedar; the mustiness accumulates with sips.
3rd. Smoother, rounder. This is good.
4th. Has body, grown up. The cedar comes forward.
5th. The sweetness of the verbena now really comes through, and the wood. It is brash, past. It will only weaken and simplify.
The third and fourth trials were the best.

The nettle became rich and savoury - successful, though perhaps more suited to a broth than a tea.

Then fireweed. There are six trials: two parameters of fermentation start ('aired/sealed') and stop ('air-dried/steamed/toasted').
The toasted ones are very smoky - only the second brewing was remotely palatable, the first too brash, the third already stale. Shall I toast differently?
I prefer the steamed - the air-dried are olivey, too vegetal. The steamed are delicate with good balance and light body for me.
Others liked the air-dried, perhaps for the particular aromas.
Overall I think I prefer the sealed ones - the flavour is stronger and more complex.

For next season, focus on fireweed, and inoculate with A. niger.

I learned from Sara that A. niger is fond of higher temperatures, 30-37˚C.

While some of these applications were interesting and potentially useful for something, they did not get at the heart of the matter—which is to say that I still wanted to drink some tea, and I wasn't yet there.

Part 2—Fireweed

At this point I need to depart temporarily from pu-erh, and focus in on fireweed. Ben had found an entry in a Swedish herbal about how people used to make tea from fireweed, and sent it my way. I made first fireweed trials that summer of 2013, and promptly fell down the fireweed hole.

It turns out fireweed has quite a lot to do (culturally at least) with the tea plant, that is, Camellia sinensis. Fireweed tea was also called Koporye tea in Russia, after the area of Koporye west of St. Petersburg near the Gulf of Finland, where in the 1800s producing fireweed tea was the main source of income. Inhabitants of this region even burned forest in order to stimulate the growth of the plant. It seems that despite not containing caffeine, the sensory properties of fireweed, properly processed, could become so similar to Chinese tea made from Camellia sinensis that it could be and was used in place of the real thing. Some unscrupulous merchants are reported to have cut their imports of 'real' Chinese tea with up to 40% Koporye tea, which was only discovered once their accounts showed they had sold twice as much tea as they had imported! (Ljungkvist, 2011)

Here was a plant with some proven potential. Fireweed's binomial is Chamerion angustifolium, formerly Epilobium angustifolium. The Chamerion genus has eight species, all of which are perennial and restricted to the northern Hemisphere. C. angustifolium and its close relative C. latifolium are circumboreal and circumarctic, while the six others are native only to Eurasia. Like many 'wild' plants fireweed has a great many vernacular names: willow herb, blooming sally, purple rocket, rickup, wicopy, and many variations on the theme. And that is just English—there are supposedly over 85 different names for the plant in Swedish (ibid.).


Fireweed is a robust perennial, growing .5-3m tall. It has fine roots and rhizomes, extending down to 45cm in the soil, purplish stems, narrow leaves around 3-20cm long, pink/magenta four-petalled flowers ~2-3cm in diameter, and long slender fruits of a similar colour to the flower. In late summer when the fruits dry they burst open and release long-haired seeds to the wind. The plant can reproduce both sexually (through flowering) and asexually (vegetative reproduction through rhizomes), depending on climate and environmental pressures. So awesome! Imagine if we could do that.


In addition to the leaves being used for tea, different parts of the plant have been used for food and medicine by people around the Northern Hemisphere where it is found: the young shoots as a vegetable similar to asparagus, the young leaves as a green, the roots as another vegetable and sometimes roasted and brewed as a coffee substitute (best before the plant flowers), the flowers made into jelly (ibid.). The plant has been used in both European and North American folk medicine traditions to soothe skin irritation and burns, and brewed into a tea to relieve stomach upset, respiratory difficulties, constipation, prostate conditions and urinary difficulties (PFAF, 2012). There is even production of monofloral fireweed honey in Alaska, as well as reports of an ale made with fireweed in Kamchatka, whose intoxicating factor was bolstered with the addition of the hallucinogenic fly agaric mushroom Amanita muscaria.

Other non-edible uses include cordage from the fibre of the outer stems, stuffing material and tinder from the seed hairs, and a protection from the cold from the powdered inner cortex when applied to exposed skin. At one point some enterprising Swedes tried to make a cotton-like textile from the fibrous seed hairs, but it didn't work so well (Ljungqvist, 2011).

Fireweed is common in a variety of ecosystems: by streams, in uplands, coniferous and mixed forests, aspen parklands, grasslands, and bogs. It quickly colonises disturbed habitats, such as logged areas, deglaciated land, avalanche zones, highway and railway embankments, old fields, and burned areas (hence 'fireweed'). During the Second World War, fireweed also came to be known as ‘bombweed’ due to its proliferation in bomb craters. The plant can handle shade but grows best in open locations with direct light, and prefers acidic soil. It is easily cultivated, growing best in soil with good drainage but that also retains moisture, yet it can also grow in many other conditions. It is hardy to -20˚C. Fireweed is currently only cultivated as a soil stabiliser, and because of its widespread distribution across the Northern Hemisphere it is quite easily harvested locally, including in Denmark and Scandinavia. 

Fireweed after a forest fire.

Fireweed after a forest fire.

I learned about fireweed in the middle of the summer 2013, too late to work with the tender young shoots and barely catching the end of the younger leaves—the best candidates for making tea. The younger leaves can be quite delicate, with a bright, fresh-olive aroma and a slight bitterness. The flowers are gently fragrant with a hint of sweetness. When oxidised, the leaves take on a dark colour and various notes of black tea and fruit. When fermented, they develop notes of fermented olives and brine. I began working with more mature specimens to get a feel for the plant and how it responded to the technique, making trials on how to initiate, direct and stop oxidation, and bode my time until the following season.

At the end of the summer, I took a trip to the Danish island of Bornholm with my friend Josh Pollen (he's a chef in London who runs Blanch & Shock together with his partner Mike Knowlden, and he's spent some time with us before). We spent three days biking around the island, eating mirabelles, getting lost on logging roads, and camping on the beach. It is a beautiful island.

Josh chilling in a sea of wood sorrel

Josh chilling in a sea of wood sorrel

On our last night, we went to Kadeau Bornholm, the first time for us both. After our meal, we hung out with some of the team, and when we told them we were sleeping in the beach dunes below the restaurant that night they invited us to staff breakfast the following morning. After breakfast, Markus Junkala, one of the sous-chefs who has since become a great collaborator, gave us a tour and showed us a bunch of things they were working on, one of which was——fireweed tea! The coincidence was too funny. We agreed once the season had finished on the island, we would meet back in Copenhagen and plan some collaborative R&D for the spring.

Part 3—Making tea

At the start of June 2014 I went to Bornholm to work further with Markus on developing a fireweed tea we wanted to drink. Here are my tea-related notes from that time.

tea - focus on fireweed. start with oxidation, develop technique. then layer A. niger on top. to serve alone, in a blend, and also to make a variety. 

Markus leading the way to forage beach coriander.

Markus leading the way to forage beach coriander.

Fireweed leaves stripped from the stem

Fireweed leaves stripped from the stem

fireweed. harvested kl.930. left in plastic garbage bag all day to begin to wilt. picked leaves at kl.18, crushed by hand, oxidation begun kl.19. bashed with rolling pins in gastros kl.23 to increase oxidation (the kitchen guys thought we were crazy).
The plan for the fireweed is to do a bit more of a structured process, to figure out what we think works best. So far, our variables are:
fermentation method: under weight, under vacuum
fermentation time: 2 days, 3 days
fermentation halting method: dehydrating, sun-drying, steaming, roasting
This matrix yields 16 trials.
Other possible variables to explore include oxidation method, oxidation time, fermentation temperature, storage method, and post-fermentation moulding with
A. niger.

Fireweed leaves ready to begin oxidation.

Fireweed leaves ready to begin oxidation.

fireweed tea - begun fermentations kl.1030.

fireweed tea - quite aromatic actually. tasted and taken off fermenting kl 17.
fireweed - Markus will split batches tuesday[10.7]/wednesday[11.7] into 4 and stop fermentation using 4 methods: dehydrate, sun-dry, steam, roast. label, vacuum and freeze until tasting.

Over those few days in June the weather was glorious, sunny and hot—hence our optimism and excitement with being able to use sun-drying as a processing method. On Tuesday the 10th and Wednesday the 11th, however—the days Markus was to halt the fermentation—the sun had disappeared, so he removed the 'sun-dried' variable from the trials. Which was just as well because nine trials was enough for one tasting, let alone sixteen.

I returned for a few days in the middle of July to work further.

the onion cress tea worked last time![summer 2013 by Markus] try with more alliums, maybe green leek tops
fireweed - keeping flowers in yields red berry smells

[This day we conducted a tasting trial, along with Nicolai, Magnus and Rasmus, the trio behind the restaurant. We also began applying the techniques to plants other than fireweed to see what happened]
tea taste trial. 8 fireweed trials + 1 just lightly oxidised version:

Trials for double-blind tasting 1, July 2014 at Kadeau Bornholm, with unfermented control (#9). Two brewings were tasted, and none from the second were preferred. If only I knew how to represent matrices in three dimensions, it would be much prettier.. 

Trials for double-blind tasting 1, July 2014 at Kadeau Bornholm, with unfermented control (#9). Two brewings were tasted, and none from the second were preferred. If only I knew how to represent matrices in three dimensions, it would be much prettier.. 

Bashing fig leaves with a rolling pin. A bit crude, but it was a first trial..

Bashing fig leaves with a rolling pin. A bit crude, but it was a first trial..

trials 1 and 7 are best for further development, as well as 2 and 9. It seems the non-vacced are preferred, with the steamed preferred at 2 days and the roasted at 3. [This could be because the container-fermented leaves have more internal variability and thus develop a greater range of flavour, whereas the vacuum-sealed leaves have quite a consistent environment and so the range is more narrow.. just a hypothesis.. in any case the more delicate flavour after 2 days makes more sense for steaming, and the stronger flavour after 3 for roasting. The best steamed trials were appreciated for their balanced taste and herbal/floral notes, while the best roasted trials were enjoyed for their fuller tannins and noted similarity to earl grey.]
processing other teas: fig leaf, kohlrabi leaf, meadowsweet leaves, angelica leaves, tansy leaves. started oxidising, and fermenting at end of night.

teas - more control trials of
lightly oxidised then dried/steamed; and further trials with the flowers: with leaves included during oxidation/fermentation, as well as excluded, dried and then added to the processed tea.
other teas: post-fermentation processing for fig leaf, meadowsweet, tansy, kohlrabi. the kohlrabi is disgusting and farty and rotten - tossed. the meadowsweet isn’t so fermented, it is quite sturdy - sealed full and kept longer. 


Trials for blind tasting 2, November 2014 at Kadeau København. Two brewings were tasted. All trials had standard 2-day fermentation in container.

Trials for blind tasting 2, November 2014 at Kadeau København. Two brewings were tasted. All trials had standard 2-day fermentation in container.

brewing method: 2.5g in bag / 100ml, pulled at 1 min; re-brewed
with flowers - we seem to prefer roasted ones (batches 5 and 8), as well as batch 6, with dried flowers added after fermentation and drying. in general, those processed with flowers (3-5) get too soapy. 6 may be better in second brewing, lactic notes are more mild. otherwise, 1st brewing is best and very aromatic.
meadowsweet - 9 (ofd) is best. the others lose the meadowsweet flavour. perhaps needs less processing eg. only 1 day fermentation.
fig - 12 (ofd) is horrible; 13 (ofsd) is better and preserves some of the fig/coconut flavour. none are good enough by themselves, maybe blended with other teas, and/or with fresh leaves. or maybe tincture is just better for the fig leaf!
tansy - amazing smells! all so incredibly bitter! perfect rotovap potential, to separate the top notes from the bitter taste compounds.
angelica - definitely savoury broth territory. 19 (ofsd) and 20 (ofr) are best, and give a fantastic tingling sensation. could be great mixed with fresh/dried angelica leaves for more of those angelica top notes. these have loads of body. use with something fatty! like pork, or lamb neck.  

By this point we had gained a few different directions to take the research: developing a tea to drink, especially as a post-prandial; and using a similar technique to supercharge the flavours of many different plants for savoury applications—especially plants, like fireweed, that don't have so much flavour in their raw form, or have a nice aroma but a tough, sturdy, or fibrous texture that does not lend the leaves well to being eaten directly, either raw or cooked (like fig leaves, and mature leaves of tansy, angelica, meadowsweet, and many others).

And now, at last, a recipe. Here is the protocol Markus and I developed for a basic fireweed tea, which can be conjugated further for all sorts of other plants.

Fireweed tea

1. Harvest a bunch of fireweed. Cut the stalk just below the last useable leaf—depending on the fineness of the tea this could be anywhere from just the tip to the tenth leaf or more.
2. Pick. Bring the fireweed back to your working area. Pick off the leaves from the stem, and, if wanting to make different grades, sort into different sizes. Discard any leaves that are brown, dried, or otherwise not intact.
3. Oxidise. Depending on the amount of leaves and available time, this can be done by rolling and/or crushing the leaves with one's hands, bashing them with a rolling pin in a gastrotray, or other methods which we invite you to dream up.
4. Develop flavour. Let the leaves sit to oxidise and develop flavour—this length of time can be however long or short one prefers, although we tended to let it go for at least a couple hours and no more than twelve. We found the tea turned out best when the oxidising leaves were at the height of aromatic intensity.
5. Ferment. Put the oxidised leaves into a container and place another container of identical size on top, pressing firmly so the leaves compact and become more or less 'sealed' in the bottom container. Allow the leaves to ferment at ambient temperature for 2-3 days (or less or more) depending on the plant and the desired result.
6. Halt fermentation. Once the leaves have fermented, remove from the container and halt the fermentation by dehydrating, steaming, roasting, or any other technique you prefer for dispatching bacteria (except maybe not bleach).
7. Store. Once the fermenting leaves have been turned into non-fermenting leaves, ensure the leaves are sufficiently dry and have cooled to ambient temperature, then store. We prefer sealing at partial vacuum (to remove as much air from the bag as possible without crushing the leaves) and keeping cool and dark, to prevent further oxidation from light, heat, or oxygen or from taking up other unwanted aromas.
8. Brew. The standard procedure for (black) tea sensory analysis (I have since read) is 3g of tea to 150mL boiling water, infused for 5 minutes then poured for evaluation (Kan et al., 2004). Of course, one may brew the tea however one may wish, which will also change depending on the processing method (we have found toasted/roasted teas can handle higher brewing temperatures), the desired profile, and the culinary function.

Future things to test:
- separate fireweed leaves into different grades depending on the size and conditions of harvest, as do producers of high-quality tea
- sun-drying versus dehydrating to halt fermentation
- different oxidation methods
- different oxidation times
- different fermentation temperatures (all of these trials were conducted at warm summer room temperature, mid-to-high 20s)
- different post-processing storage methods (these trials were sealed with a partial vacuum and stored in the freezer)
- try all sorts of tough plants with flavour potential, especially parts of plants often thrown away like tough parts of leeks, tomato leaves, etc.
- and last but not least, now we have a method to which to add the extra layer of fermentation with Aspergillus niger! I want to make fireweed Pu-erh, build a pressing mould and press it into bricks, age it and see what happens—that's what's next..

Fireweed outside the window of the train, north of Copenhagen. Now I see fireweed everywhere I go..

Fireweed outside the window of the train, north of Copenhagen. Now I see fireweed everywhere I go..


Many thanks to:
Sara Landvik for plating up our sources of Aspergillus niger;
Josh Pollen as the quintessential comrade;
Markus Junkala for being a brilliant partner-in-crime;
Nicolai Nørregaard and the whole team at Kadeau for hosting me and giving me and Markus time and space to carry out our research on Bornholm and in Copenhagen;
Max McCurdy in Tokyo for that memorable pu-erh-fueled evening in November 2014;
and of course many members of the NFL team past and present.


Blumenthal, Cynthia. 2004. Production of toxic metabolites in Aspergillus niger, Aspergillus oryzae, and Trichoderma reesei: justification of mycotoxin testing in food grade enzyme preparations derived from the three fungi. Regulatory Toxicology and Pharmacology. 39: 214-228.

'Chamerion angustifolium'. Wikipedia. Accessed 12.1.16. <>.

'Chamerion angustifolium (L.) Holub (Fireweed)'. Agriculture and Agri-Food Canada. Government of Canada. Updated 23.1.2012. Accessed 19.11.13. <>.

'Epilobium angustifolium L.'. Plants for a Future. Updated 2012. Accessed 19.11.13. <>.

Kan, Tze-Neng et al. 'Chapter 46: Partially Fermented Tea'. In Handbook of Food and Beverage Fermentation Technology, ed. Y.H. Yui et al. New York: Marcel Dekker, 2004.

Ljungqvist, Kerstin. 2011. 'Mjölkört'. Nyttans Växter. Calluna: Sweden. pp297-8.

Pavek, Diane S. 'Chamerion angustifolium'. Fire Effects Information System [Online]. U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station, Fire Sciences Laboratory. 2009. Accessed 19.11.13. <>.


Fractioning insect garums

Added on by Josh Evans.

by Josh Evans

In the beginning, our original grasshopper garum recipe yielded one product: grasshopper garum. Sometimes we also used the paste.

400 g whole grasshoppers
600 g wax moth larvae
225 g pearled barley koji
300 g filtered water
240 g salt

Blend insects until broken up but not into a smooth purée and keep in a container. Mix insect purée, barley, water and salt together. Place in a non-reactive container with cling film directly covering the surface. Place container in a 40˚C incubator or suitable area, and allow at least 10 weeks to ferment. The garum will separate and remain on the bottom of the vessel, and should be decanted/siphoned with an appropriate pipette/tube. The paste is also excellent, and should be passed through a fine sauce net.

In the summer of 2013, we began to make two 'pressings', as one does with olive oil. The first 'pressing' involved filtering the fermented mixture through a filter paper solely by gravity, obtaining a translucent liquid with few impurities—we called this 'Extra Virgin Grasshopper Garum'. The second pressing actually involved some real pressing, where we took what remained in the filter and pressed it through a superbag to obtain 'Second Press Grasshopper Garum', analogous in some sense to pomace oil.

Extra Virgin Grasshopper Garum on the equator in Uganda.

Extra Virgin Grasshopper Garum on the equator in Uganda.

Last summer, in 2015, we took things a bit further. Firstly, we made production batches of five 'single-species' garums using the same basic recipe as the original, and only one species per batch (based on trials we had conducted the previous summer, in 2014). The species were: grasshopper (Locusta migratoria), cricket (Acheta domesticus), wax moth larvae (Galleria mellonella), bee larvae (Apis mellifera), and mealworm (Tenebrio molitor).

1000 g insects (55.9%)
250 g barley koji (14%)
300 g water (16.8%)
240 g salt (13.4%)
Incubate at 40°C  for >10 weeks
Filter, bottle, pasteurise at 72°C for 15s

When it came time to filter, we realised that we could go into more detail than we had before—particularly because we had Bernat's PhD rigour with us, and were thus well-positioned to go deeper into the post-fermentation part of the process.

Figure 1. Flow chart drawn by Bernat illustrating our most recent garum fractioning process.

Figure 1. Flow chart drawn by Bernat illustrating our most recent garum fractioning process.

We began with the complete garum mixture, post-fermentation. We passed this mixture through a chinois without filter paper, to begin to separate the liquid and solid phases. We then let the liquid phase pass through filter paper by gravity, yielding a fine liquid that had passed through the paper and an emulsion left on it, which we suspect contained residual compounds and water suspended in fats. The filtered liquid we allowed to further separate into lipid and water phases, yielding 'Virgin Oil' and 'Insect Garum 1st fraction' respectively. We passed the emulsion left in the filter paper through a sauce net and called it 'Paste B'—because we were not expecting to have it and had already named its analogue 'Paste A'.

Fractioning garums by gravity through filter paper.

Fractioning garums by gravity through filter paper.

Meanwhile, the solids reserved from the very first filtration through the chinois we pressed through a superbag, yielding a cloudy liquid, and a bit of solids—mainly chitin, small bits of barley etc.—that we discarded. The liquid we then let pass through a superbag by gravity, yielding a more opaque liquid than the 1st fraction, which we called 'Insect Garum 2nd fraction', and an emulsion left in the superbag that we called 'Paste A'.

We also tried using a vacuum filter to extract more of the liquid, but that didn't end up working so well..

Bernat and the vacuum filter. We had high hopes.

Bernat and the vacuum filter. We had high hopes.

Bernat and Roberto try to collaborate with the vacuum filter

Bernat and Roberto try to collaborate with the vacuum filter

Good old gravity took a bit longer but yielded a better product.

Thus, in total, we obtained five products from this fractioning process: Virgin Oil, Garum 1st fraction, Garum 2nd fraction, Paste A, and Paste B.
Our more rigourous fractioning also gave us higher total yields—see Table 1, which does not take into account the Virgin Oil or Pastes A and B.

Table 1. Garum yield as a function of total starting mass. Does not include yield of Virgin Oil or Pastes A and B.

Table 1. Garum yield as a function of total starting mass. Does not include yield of Virgin Oil or Pastes A and B.

Most importantly, the single-species garums are delicious (except for the Mealworm, which is quite thin and unremarkable) and distinct from one another. We are keen on experimenting further with the pastes, which are just as distinct in taste as the garums—they range in colour from pastel peach to ombré ochre, and some of them have a unique, silky texture. Tobyn started working on some compound butters; we can imagine particular pastes being well-suited to different particular applications.

The range of pastes.

The range of pastes.

Now the next step is to re-obtain a centrifuge and take the fractioning further—and to see for what, if anything, we can use the discarded fragments of exoskeleton..

Faux foie

Added on by Josh Evans.

by Josh Evans

4 October 2012—the day before Ben and I departed on a research trip to the Netherlands, we took a bunch of kojis we had made from different nuts, seeds, and grains, cooked up a bunch of pulses, raided our dry store for aromatic things, boiled a big pot of brine and bashed together a bunch of sauces to start fermenting. The method was deliberate madness, mixing and matching kojis, cooked pulses, aromatics and brine in ratios that seemed to work based on similar previous trials and tasting as we went. Textbook shotgun approach.

Three months later, in January, we had a tasting.

Of the twelve trials, we kept seven that had further potential and tossed five that were horrid. One of the former was particularly exciting—it was unmistakably reminiscent of foie gras, with that fatty, nutty taste and rich mouthfeel, and made only of plant-based ingredients. We called it 'faux foie'.

Original faux foie

500g koji (quinoa) 
250g koji (4 parts nøgen byg 43: 1 sunflower seeds)
750g cooked butterbeans
30g dry morels
500g bean stock
1L 20+% brine (6.2% salt in total mixture)

Combine in a sterilised container. Cover the surface of the mixture with plastic wrap and store for three months.

Since then, we tried to take the recipe further by tweaking the quantity of morels and trying out different types of barley for the koji, but we weren't able to achieve the results we were looking for.

We went back to try to replicate the original recipe, even using the remaining amount of the original batch to inoculate the new trials, and still weren't able to reproduce it exactly. Such is the nature of serendipitous success I suppose. We will keep trying.

On measuring

Added on by Josh Evans.

by Josh Evans and Arielle Johnson

‘2% salt’. How many times has this phrase passed our lips? By the summer of 2013 we were realising that this simple edict, the core of many lacto-fermentation recipes, contained a crucial ambiguity. This post is an attempt to explore and clarify how different cultures—namely, those of the kitchen and the laboratory—measure things differently, and why it matters.

The problem

Many of the recipes and processes we talk about on this blog scale according to ratios. For example, for a typical lacto-fermentation, rather than starting with 1000 grams of vegetables and 20 grams of salt, it is simpler to weigh the vegetables you have and add 2% salt to them. 

But what do we mean when we say “2% salt” or “25% sugar”? A chef might, when presented with 1000 grams of something to which they need to add 25% sugar, add 250 grams of sugar—since 250g is 25% of 1000g. On the other hand, to a scientist, a mixture of fruits with 25% sugar isn't 1000g of fruits and 250g of sugar, but a mixture where 25% of the total weight is sugar: and if you started with 1000g of fruit, this total mixture will weigh 1333g and have 333g sugar in it, since 333/1333=25%. In fact, the mixture of 1000g of fruit plus 250g of sugar now only contains 20% sugar by composition, since the total weight is 1000g+250g=1250g, and 250/1250=20%. This difference could lead to problems if the 25% level of sugar was very necessary to reach! 

And, unfortunately, while this gap is negligible for small percentage additions—taking “add 5% salt” to mean adding 50g of salt to 1000g of something will yield a mixture that is 4.76% salt by composition, which is pretty close—it gets bigger and bigger as the desired percentage increases, so the potential for error gets increasingly larger as the amount to add goes up: 10% vs. 9.1% is maybe not so big (maybe), but 35% vs. 25% definitely is pretty big.


As we mulled this problem over, different ways of representing this distinction emerged.
At the core of the issue is the relationship between the parts of a mixture and the whole. What varies is the relation’s direction—whether one is going from the former to the latter or vice versa.

1. ‘Process’ vs. ‘Product’
Our first framework for conceptualising this difference was ‘process’ vs. ‘product’: ‘process percentage’ for the easy-to-use number of what you actually need to add, in terms of the weight of what you are adding it to; and ‘product percentage’ for the percentage of what, by mass, is actually in the final mixture. These words capture the distinction neatly, but they may not be different enough to make an elegant notation with—to indicate which percentage we were using in our notes and results, which was the ultimate goal. So we kept brainstorming.

Figure 1. Word clouds of brainstormed terms for both methods of measurement

Figure 1. Word clouds of brainstormed terms for both methods of measurement

2. ‘Factor’ vs. ‘Ratio’
Another way to frame the distinction was one Justine sent over last March (you can see how long it’s been haunting us):

Justine: “I don't know why it is just recently that I have been re-thinking about it, but I might have something to add to the conversation about percentages in food. I don't know if it is still a issue in the lab, but anyways, I think you might be interested by my recent thoughts on it. I think it came because I had to explain my students about fermentation (always!). I suddenly remembered another scientific way to express a relative quantity. In science, when you have to do a 10% solution of something, you can either notate it with the % sign, or with the dilution factor 1:10. The factor means, for all scientists, that you have one part of something in a final volume of 10, so 1:10 is 1 part of something and 9 part of the other, always.
I guess you have to be careful in the lab and not confuse it with a ratio (like we did for some fermentation recipes, ex: 1:5:9).
Maybe you could add 'ratio' or 'factor' in front of each notation!”

Josh: “So if we were to write 1:10 for something, it's sort of like the 'scientific' or 'composition' measurement of 'factor' would read like '1 in 10 parts x', and the 'chef' or 'production' measurement of 'ratio' would read like '1 to 10 parts x'. Yet another way of illustrating the difference...”

Justine: “Factor is 1 of x and 9 of y for a total of 10xy; ratio is 1 of x and 10 of y for a total of 11xy. Maybe you can start a new way of writing and add some symbol to refer to what you are talking about, maybe an 'f' or a 'r' after the fraction, i.e. 1:10(f) for the former and 1:10(r) for the latter.”

3. ‘Production’ vs. ‘Composition’
The possibilities branched rapidly and recursively. We ultimately settled on using mainly percentage notation instead of ratios, but both modes could be used depending on one’s preference (and Justine’s ‘Factor/Ratio’ notation could work well for the latter). Since I (Josh) have been mainly using percentages, I settled for a while on ‘Production’ and ‘Composition’ as my terms, which I notated with %P and %C and which correspond, respectively, to Arielle’s and my original proposal of ‘process’ and ‘product’.

4. ‘Pluscent’ vs. ‘Percent’
I still wasn’t 100%C satisfied with this notation, because while it worked well enough (not brilliantly, but fine) in writing, it was clunky to say: “production percentage” is six syllables! It was only a few weeks ago, while finalising this draft, that the best solution so far emerged from the ether. Actually, it emerged from the keen mind of a friend named Dave Rowe, while he, his wife Pam and I were sharing a glass of wine and I was describing to them my on-going wrestling match with percentages. Dave’s observation was that perhaps we should look at the word ‘percent’ itself as a starting point from which to generate an entirely new term to distinguish between the two methods. He quickly did so by suggesting the neologism ‘pluscent’ (a percentage that ‘is added’ to 100) as the logical counterpoint to ‘percent’ (a percentage out of 100). My follow-up question to Dave was how he would notate a ‘pluscentage’, to which he suggested that we create a new symbol—we collectively arrived at the idea of combining ‘+’ with ‘%'. On platforms such as our website that do not allow such custom fonts in-text, I have settled for using '+%' in combination; otherwise, here is the glyph we designed (thanks to Rosemary, a former NFL intern and Artist-in-residence) and rendered as a font (thanks to Rosemary's friend Daniel, a graphic and web designer).

Visualising the gap

Table 1. Increasing gap between pluscentage and percentage for given weights.

Table 1. Increasing gap between pluscentage and percentage for given weights.

Figure 2. Gap between percentage (plotted on the y axis) and pluscentage (plotted on the x axis). The curve gets shallower, which shows how percentage drops off more as pluscentage increases.

Figure 2. Gap between percentage (plotted on the y axis) and pluscentage (plotted on the x axis). The curve gets shallower, which shows how percentage drops off more as pluscentage increases.

Figure 3. Absolute difference between percentage and pluscentage. The curve gets steeper—the difference between percentage and pluscentage gets bigger faster—as the percent-number increases.

Figure 3. Absolute difference between percentage and pluscentage. The curve gets steeper—the difference between percentage and pluscentage gets bigger faster—as the percent-number increases.

Formulae and calculators

So, when it comes to making things, if one needs to reach a certain percent of an ingredient in the final mixture, one must bust out some algebra.
Given the weight of the mixture to be added to, it is necessary to solve for x: 

x = az


a = 100b/(100-b)

x is the amount to add;
z is the amount to be added to;
a is the pluscent of the addition; and
b is the percent of the addition in the final mixture.

But fortunately, you don't have to do that, because we made a calculator. Actually, three. The ‘Pluscent calculator’ can be used to calculate pluscent, given the desired percent of the addition in the final mixture; the ‘Addition calculator’ can be used to calculate addition amount, given the weight of the mixture to be added to and the desired percent of the addition in the final mixture; and the 'Percent calculator' can be used to calculate the percent of an addition in a final mixture, given the pluscent (the opposite of the first).

For example: You are making a garum. Let’s say you have 2730g mackerel guts and 600g barley koji, and you want to figure out how much salt to add to reach, say, 12% in the final mixture. You would use the ‘Addition calculator’, put ‘3330’ (2730+600) in the first field, ‘12’ in the second field, and obtain a figure of 454g.
If you wanted to figure out the pluscent for the salt, you would use the ‘Pluscent calculator’, insert ‘12’, and obtain 13.63.
And let’s say you were working from a garum recipe for which you already had the salt pluscent, and wanted to know the salt percent in the final mixture. You would use the ‘Percent calculator’, insert ’13.63’, and obtain 12.

Further considerations

Of course, this calculator only works if you're dealing with 2 components—though one component can be composite, eg. the mixture of mackerel guts and koji in the example above. For multi-component ratios (salt : koji : legumes for a miso, for example) we’d have to make a more complex calculator, but it can be done.

The two measuring methods explored here are not the only ones out there. Baker’s percentages, for example, work differently—one ingredient, usually the most massive but also sometimes the most valuable, is set as a reference (100%), and the amount of every other ingredient is scaled as a percentage of the reference’s weight. Pluscentage can be thought of as the simplest baker’s percentage, where there are only two ‘ingredients’: the one to add and the one (or mixture of ingredients) to be added to. The advantage of baker’s percentages is that they can be used for more ingredients; the advantage of pluscentage might be that its relationship with percentage is more easily calculable, especially with recipes that change. For lots more on measuring methodology, check out Modernist Cuisine vol. 1.

Furthermore, of particular note for salt in fermentations is that it is not salt itself that matters, but how salt, and other compounds like sugar, hold onto water. What we are measuring here is water activity (Aw), and it is this measurement that in part determines whether or not certain microbes are able to grow. So really, the ideal situation would be to measure salinity in relation to water in a recipe (taking average moisture contents of constituent ingredients), but of course in practice this is somewhat difficult.

An experiment

While differences between these two (or more!) ways of measuring are clear in principle, and while I have started indicating which one I use in recipes, I still want to have some data that shows it matters when it comes to taste—and above what threshold. So I devised an experiment to address the role of this one variable in the complex phenomenon of fermentation.

A certain fermentation model system will exhibit gastronomically significant differences above some threshold if only salt concentration is varied by percent and pluscent.

I made two different model fermentation systems—a low-salt miso and a high-salt miso—using Øland brown beans, pearled barley koji, filtered water, and sea salt (Table 2), in duplicate, each with three trials: one with salt by percent, one with salt by pluscent, and a negative control with no salt.

One set of duplicates before mixing; negative control not pictured.

One set of duplicates before mixing; negative control not pictured.

Table 2. Low- and high-salt miso trials varied by salt content: percent, pluscent, and none.

Table 2. Low- and high-salt miso trials varied by salt content: percent, pluscent, and none.

I took samples of ~5ml at 2-week intervals over the 3-month fermentation, for a total of 7 samplings, which are frozen and await metagenomic sequencing by Martin Abel-Kistrup and Tom Gilbert, part of the Gilbert Group at the Centre for GeoGenetics at the Natural History Museum of Denmark, University of Copenhagen. We have already collaborated with Martin and Tom on doing some metagenomic sequencing of the microbial ecologies of some of our vinegar barrels; this should be an interesting next experiment.
I conducted a fast aroma and visual analysis after sampling for the seventh and final time and transferring the remainders of the final products to clean containers for cool storage.

See Table 3 for some notes from the informal aroma and visual analysis I conducted.

Table 3. Fast sensory analysis notes from the different samples.

Table 3. Fast sensory analysis notes from the different samples.

This is a very preliminary experiment, and it’s not yet done. It would be ideal to obtain more, and more rigourous, sensory analysis data (include tasting in addition to looking and smelling, gather sensory descriptors, serve samples blind, use ~10 panelists), and I'm dying to sequence the metagenomes of the samples to see if there are some differences in the microbial populations. Based on the preliminary results, I’d say it’s likely there are some differences happening in the microbial communities of the different samples.

Finally, I’m sure others have already thought about this measurement problem and come up with more elegant solutions for conceptualising, terming, and notating the different methods. It would be great to hear from you if you know of any existing materials.
In the meantime I'm finding ‘pluscent’ and ‘percent’ pretty useful.

If you would like to use the pluscent symbol yourself, you can download the font here. The pluscent symbol is the only glyph in the font, and is inserted with the '%' key (shift+5 on English keyboards).

Anna and I taking our first samples.

Anna and I taking our first samples.


We’d like to thank Justine, Guillemette, and other numbers-geekery-inclined team members past and present for contributing to this ongoing discussion; Dave Rowe and Pamela Camerra-Rowe for the stroke of brilliance that provided the world with ‘pluscent’ and the idea for its symbol; and Rosemary Liss and Daniel Givens for contributing their time and skills in creating the pluscent symbol in Illustrator and rendering it into a font with Fontello. Also many thanks to Anna Sigrithur for taking samples by herself multiple times while I was traveling in the fall.


Myhrvold, N. et al. Modernist Cuisine: The Art and Science of Cooking. USA: The Cooking Lab, 2011.


Added on by Josh Evans.

by Josh Evans

At the end of the year in 2014, a month or so after moving into our new space, we had a Julefrokost to celebrate the year. I made a simple experiment with a few of my favourite items in the lab at the time: Jason's fermented giant puffball, quince balsamic/elder vinegar 'lees', and fireweed tea.

In some way it was quite old-school, banal even: a blade of raw endive with accoutrements. The endive provided fresh bitter snap for what made it, for me, other than an entirely predictable hors d'oeuvre.

I was inspired by Jason's fermented giant puffball mushrooms—nondescript yet potent gems of unsuspecting umami. Shaved thinly, it provided the savoury horsepower.

In the winter of 2013, we were making a new batch of quince wine to top up our balsamic vinegar barrels just around the time we were also bottling the 'older elder' vinegar begun in the summer and fermented through the fall. We had a bit of extra quince wine, to which we added the extremely vigourous mother from the most successful batch of older elder vinegar. Left for six months in a warm cupboard on the boat, the mixture fermented and reduced into a thick, dark, exceptionally sour thing. We don't know quite what to call it (a not infrequent problem) but it is tasty. Informally I have been calling it 'quince vinegar lees'—not accurate but perhaps better than nothing. A little of it goes a long way.

At a first tasting it clearly needed some fat, and Roberto suggested using a nut oil, like walnut or hazelnut. I settled on a blend of both, incorporating the former's structure and the latter's aroma, and making a vinaigrette of sorts with the quince vinegar lees to brush into the endive before adding some wisps of fermented puffball.

It was still quite 'classic'. I thickened the vinaigrette and flipped the endive over.

I had powdered some of the fireweed tea as a final garnish, for a tannic, lightly lactic note up front.

An informal synthesis of compelling things at hand.

There was a lot of tasty food that night, a great end to a full year.

Aged Butter part 4: Blue Butter

Added on by Johnny Drain.

by Johnny Drain

This series is about oxidation, rancidity, and aging butter. Part 1 gave some background about butter, rancidity and the cultural context for eating aged butter. Part 2 explored the science of oxidation in fats and the safety of eating them. Part 3 was on culturing butters with unusual sources of bacteria. This part (finally!) is all about aging butter.

The primary aim of the project was to see if we could, by controlling the extent and pathways of aging, create butters with novel and desirable flavour profiles. Having settled on a flavoursome cultured butter, we started to carry out tests to control the conditions that lead to rancidification (as were laid out in part 2).

My hope at the start of the project was that, by letting the butter age and therefore develop mild rancid characteristics, the delicious butter cultured with our unique combination of LAB could be enhanced by some of the blue cheese and spicy notes characteristic of rancidity to give rise to an even more interesting, delicious butter: a product that, if we were to put our branding and marketing exec hats on, we might best call ‘Blue Butter’.

Figure 1. Butter samples using various, sometimes improvised, techniques to control the conditions they were exposed to.

Figure 1. Butter samples using various, sometimes improvised, techniques to control the conditions they were exposed to.

So we exposed butter samples to a variety of different conditions for a period of up to 45 days: we vacuum-packed samples or left them exposed to oxygen in the air; we exposed samples to direct sunlight or kept them in the dark; we froze samples, refrigerated them, or kept them at room temperature. Would combinations of these processes produce notably different flavour profiles, and, more importantly, would any of these combinations offer promising gastronomic results?

Aged butters, cultured and uncultured

I ran simultaneous tests on cultured and uncultured butters, using the latter as a control for the former. The fresh uncultured butter was quite tasteless: thus, the effects on flavour of exposure to oxygen, light and different temperatures (as opposed to microbial activity) would, we hoped, be quite clearly discernible.

As expected, freezing the butters greatly slowed down any oxidation, hydrolysis or microbial activity and the flavours of these samples remained constant. Refrigeration did much the same. We corroborated these results with TBARS tests that showed only very tiny levels of oxidation products for chilled and frozen samples of both the cultured and uncultured butters (TBARS tests are a simple way to measure oxidation products, and they are discussed more fully in the addendum).

As the room-temperature butters were aged, a translucent ‘rind’ developed on their surface and various new aromas (eg. baby vomit—butyric acid!, blue cheese, Parmesan, linseed oil, petrol) and flavours (eg. blue cheese, Parmesan, linseed oil, spiciness, tanginess) developed. Furthermore, as the butters aged their texture became ‘smoother’ which was often pleasant.

Figure 2. Aged butters ready for taste testing

Figure 2. Aged butters ready for taste testing

For the uncultured butters there were clear differences between the flavour profiles produced by exposing the butter to atmospheric oxygen but not light and vice versa. The former gave much less palatable petrol, linseed, and beef tallow flavours, while the latter gave much more enjoyable flavours redolent of aged hard cheeses and blue cheeses. The TBARS tests supported what we intuited: that the former’s oxidation was more advanced.

The most promising results were for samples stored for ~14–28 days in dark and full or partial vacuum, or those stored for ~7–14 days in daylight and full or partial vacuum. The smens I tasted on a visit to Morocco (after I had completed this project) were very close in taste to a number of these; in particular, aged hard cheese, blue cheese and baby vomit were descriptors that cropped up when I tasted a range of smens from 3 months to 2 years old.

Table 1. Tasting notes for uncultured butter after aging for 14 days at room temperature under the stated conditions.

Table 1. Tasting notes for uncultured butter after aging for 14 days at room temperature under the stated conditions.

For the cultured butters, unfortunately beyond ~10 days almost all the samples developed an unpleasant bitterness/sourness as a result of continued microbial activity and/or breakdown of compounds produced by the culturing. To distinguish between the two pathways, one could pasteurise cultured butter to kill any living microbes before aging. However, regrettably, I didn’t have time to perform these further tests during my three-month stay—or rather, I tried but I always ended up with clarified butter (ghee), which has very different textural properties to unclarified butter.


As mentioned in part 1, smen is an aged Moroccan butter, normally made by mixing butter with an infusion of thyme or oregano and then storing for several months to several years in, traditionally, clay pots. 

Based on the encouraging results from the uncultured butter that had been kept in a full or partial vacuum and exposed to daylight, I made smens with a variety of Nordic ingredients in place of the herbs. Although their specific function in the making of smen is not documented,  oregano and thyme are packed full of antioxidants [1], as are many Danish seaweeds [2]. therefore hoped that seaweeds would work similarly well .

After 30 days, the results of the following smen infusion trials were highly mixed:
- Juniper bark—chalky, slightly soapy.
- Birch bark—resinous, sweet like candy.
- Toothed wrack seaweed—very pleasant, not a strong taste of seaweed; mild blue cheese, parmesan.
- Grass kelp—creamier and more tangy than that toothed wrack seaweed smen, and a stronger note of seaweed.
- I also made one with birch bark ash—the ash water was very alkaline—pH 13!—which caused the fat to start breaking down (saponification). The final smen had a pH of 10, which is straying towards dangerous territory so I only ate the smallest of dabs: predictably, it was soapy and unpleasant.

However, the best Nordic smen I made used bladderwrack (Fucus vesiculosus). After 15 days the bladderwrack smen tasted like a cross between a very mild blue cheese and a ranch dressing. After 30 days the blue cheese flavour had become much deeper and more rounded. I kept tasting it for up to 2 months (after which point I left the lab): throughout this period the flavour kept changing, but it remained good-tasting and, seemingly, safe. However, I suspect after 2 months in daylight it would be best to stabilise the butter by transferring it to the dark.

Seaweed smen

We served this at staff lunches melted through grains (rice, couscous or pearl barley) to which it added a complex buttery, blue cheese-like nuttiness.

25 g of crushed, dried bladderwrack seaweed
500 g fresh unsalted uncultured butter at room temperature (I also repeated this with store-bought butter (Naturmælk)

1. Infuse 500 g of water with the bladderwrack by boiling vigorously for 5 minutes. Dissolve 2 tablespoons of salt and allow to cool to body temperature.
2. In a container, pour the infusion over the butter and work them into each other. Leave overnight.
3. Strain the water off, cover and store for 2 days at room temperature.
4. Work the butter to remove any remaining water, pat the butter dry with kitchen towel and transfer to a sterilised glass jar.
5. Store at room temperature in daylight (Danish early winter daylight!).

Figure 3. Bladderwrack (Fucus vesiculosus). credit.

Figure 3. Bladderwrack (Fucus vesiculosus). credit.

Figure 4. Bladderwrack smen, one month old

Figure 4. Bladderwrack smen, one month old

Tibetan butter tea and tsampa

Tibetan butter tea is made with Yak butter that, as mentioned in part 1, is often described by Westerners as tasting rancid [3]. In Tibet and Nepal, they also use the butter tea to make tsampa, a dumpling made with roasted barley or wheat flour. Apparently the Dalai Lama eats it everyday for breakfast! Given the plenitude of funky butters I had at my disposal I was keen to try out both of these recipes.

Of the various teas hanging around in the lab, I found the most suitable was a Thai tea, Jing Shuan Oolong Tea, which, when 10 g is brewed in 450 g water for 3–4 minutes, tastes of peach and grapefruit, and has a good astringency. To make the butter tea, I mixed 50 g of tea with 5 g of butter. The aged butter that worked best was the uncultured butter that had been exposed to light but not oxygen for 1 month.

Figures 5+6. Tea, aged butter, and toasted rye flour, ready to make tsampa.

Figures 5+6. Tea, aged butter, and toasted rye flour, ready to make tsampa.

To make the tsampa, I then mixed enough butter tea with toasted rye flour to form small balls, ready to eat as they were.

The tsampa—nutty from the toasted rye, sweet and fragrant from the tea, and with a pleasing gnocchi-like texture—were quite enjoyable; I could imagine them, or some variant of them, becoming the latest go-to health craze (gluten-free, anti-oxidants from the tea etc. etc.). 

In contrast, the butter tea by itself was just a bit weird. The mouthfeel was very creamy (much like bulletproof coffee), but because of its richness it was really more like a soup; for a European—perhaps especially a Briton—the name ‘tea’ jarred strikingly with my expectations of what it ‘should’ taste like.

However, pleasingly, I did find that butter tea made with aged butter was more flavoursome and palatable than that made with normal unaged butter. Gastronomically, the butter tea didn’t seem overly ripe for investigation (e.g. I can’t see it popping up on restaurant menus any time soon). Though I can easily imagine how  in the challenging conditions of the Himalayas it is a very practical and soothing way of consuming energy in a very dense form. 


Through working on this project and the process of writing these blog posts we realised that lipid rancidity is a complex topic that is, even from a chemical perspective, not wholly understood. 

Although we didn’t produce any cultured aged butters that I was really happy with, the seaweed smens were great: their use as a flavour enhancer in e.g. stews, roasted meats and vegetables, grains, salads and dressings, could and should be pursued. It might be more difficult to control the aging process with already cultured butters, but  with some additional trials and adjustments (e.g. pasteurisation of the cultured butter to inhibit further microbial activity, followed by aging) I am confident that a cultured aged butter with unique and delicious applications can be found.

When I started the project I was probably overly ambitious; I thought it was going to be quite easy to create some form of aged butter that I could eat with bread as an analogue of blue cheese. In hindsight that was naïve of me! After all, the great cheeses of the world have been perfected with knowledge developed over many hundreds of years. From the results of the work we did, it seems that, in whatever form it is made, an aged ‘Blue Butter’ is more likely to find use as an ingredient (e.g. used to make a beurre blanc or as per the suggested uses of the smen) rather than as a standalone product.

If anyone plays around with aging butter then please let us know; we’d love to hear about your findings.

Huge thanks to everyone at the lab who made my time there so special and particularly to Josh, Michael, Mogens Larsen Andersen (University of Copenhagen) and Kent Kirschenbaum (NYU/Experimental Cuisine Collective) for illuminating chats and guidance.

[1] Jorge N., Médici Veronezi, C. and Vieira Del Ré, P. (2015). Antioxidant effect of thyme (Thymus vulgaris L.) and oregano (Origanum vulgare L.) extracts in soybean oil under thermoxidation. Journal of Food Processing and Preservation. 39(6), 1399–1406.    
[2] Farvin KS. & Jacobsen C. (2013). Phenolic compounds and antioxidant activities of selected species of seaweeds from Danish coast. Food Chemistry. 138(2-3), 1670–81. 
[3] Tuan, YF. (1969). A Historical Geography of China, Transaction Publishers, p. 96.

Addendum: TBARS

TBARS (2-Thiobarbituric acid reactive substances) tests are a relatively simple and inexpensive chemical test used to measure the extent of oxidation in a fat. They can be performed in a standard modern chemistry lab. TBARS, which include lipid hydroperoxides and aldehydes, are naturally present in systems in which lipid oxidation has taken place e.g. oxidised fats. It is generally accepted that as the level of oxidation increases so does the amount of TBARS present. 

Figures 7+8. TBARS test samples: pinker samples indicate the presence of more oxidation products.

Figures 7+8. TBARS test samples: pinker samples indicate the presence of more oxidation products.

The TBARS tests gave basic quantitative support to what we intuitively expected and determined from our tasting of the butters. See Figure 9 for some representative data.

  • For both cultured and uncultured butters, the chilled samples exhibited somewhat more oxidation than the frozen samples, and the room temperature samples exhibited much more oxidised character than the chilled ones.
  • The cultured samples always exhibited more oxidised character than their uncultured counterparts, i.e. the presence of microbes increased oxidation (probably because of increased enzymatic oxidation).
  • Samples exposed to oxygen and light exhibited more oxidised character than counterparts that had been exposed to only light or only oxygen.
  • Samples exposed to only oxygen exhibited more oxidised character than counterparts exposed to only light. That is, oxidation from atmospheric oxidation was a greater problem than photo-oxidation caused by light. A practical kitchen use of this finding would be to stress the importance of storing butter and other oxidation-prone fats vac-packed, if possible.
  • For the uncultured butter, after 23 days, the samples exposed to both light and oxygen exhibited more oxidised character than their counterparts, but only by a little bit more. In contrast, after 43 days, they exhibited significantly more oxidised character than their counterparts. This seemed to reflect how oxidation reactions are free radical reactions which have a slow induction period followed by rapid propagation step (and at some point a termination step). Due to time constraints I was unable to complete the TBARS tests on the 43-day-old cultured butters.
Figure 9. TBARS results for aged butters. Control samples were vacuum-packed and kept frozen in the dark. The results are based on single measurements and error bars were not calculated. However, the potential error size can be gauged from the discrepancy between the 23- and 43-day-old control samples (the 23-day-old one should contain less than or the same amount of TBARS as the 43-day-old one).

Figure 9. TBARS results for aged butters. Control samples were vacuum-packed and kept frozen in the dark. The results are based on single measurements and error bars were not calculated. However, the potential error size can be gauged from the discrepancy between the 23- and 43-day-old control samples (the 23-day-old one should contain less than or the same amount of TBARS as the 43-day-old one).

The results from the TBARS tests show that they are a useful and valid way of evaluating the level of oxidation in butter samples like these, that there are quantitative differences between butters stored in different conditions, and that these difference may ultimately be qualified through a combination of sensory studies, chemical analysis, and consideration of proposed reaction mechanisms.

Aged Butter part 3: culturing butter

Added on by Johnny Drain.

by Johnny Drain

This series is about oxidation, rancidity, and aging butter. Part 1 gave some background about butter, rancidity and the cultural context for eating aged butter. Part 2 explored the science of oxidation in fats and the safety of eating them. In this part I’ll describe the results of my work on culturing butters with unusual sources of bacteria, and on aging butters in Part 4. 

Found in the biome of healthy intestines, vaginas and faeces, Lactobacillus brevis might not strike you as the best thing to make butter with. However, as I found out, this pervasive bacteria, which is, reassuringly, also used in beer-making and pickling, can be used in conjunction with Finnish viili to make some top-notch cultured butter. 

Cultured butter

Butter churned from fresh cream, irrespective of the quality of the cream, is somewhat bland. To unleash the full flavour potential of butter, the cream used to make it first needs to be cultured, that is, allowed to be fermented by lactic acid bacteria. Lactic acid bacteria, henceforth LAB, are a family of bacteria that are used widely in the making of other dairy products, such as cheeses and yoghurts, and in the pickling of vegetables (sauerkraut, kimchi, nukazuke), baking, wine-making, sake-making, and the curing of fish and meats [1]. Most European butter is cultured, whereas much of the butter sold in the USA is uncultured and is known as sweet cream butter.

LAB produce lactic acid, which makes the cream more acidic (lowers its pH) and can make it taste tangy, tart, and refreshing. Some LAB can also produce a variety of aroma compounds, most notably diacetyl, which can give rise to a richer, more complex, and characteristically ‘buttery’ flavour. Diacetyl also lends richness and butteriness to Burgundy whites and Chardonnays via malolactic fermentation. In beer-making, the presence of diacetyl was seen traditionally as a flaw, but in recent years have been reclaimed by some contemporary brewers as a desirable taste property—a notable precedent for the current project, and how we hope to encourage people to re-examine how oxidised and rancid characteristics might contribute similarly positive properties to butter.

Unpasteurised milk, and therefore cream, naturally contains a variety of LAB strains, alongside many other microbes. LAB are also present in the air, on plants, on our skin, and all around us; traditionally, spontaneous culturing of cream in an open vat was how cultured butter was made. Today, cultured butter, even that made by non-industrialised processes, is often made from cream that has been pasteurised and then had cultures of known bacteria added to it.

Lactic acid bacteria

During fermentation, LAB use lactose (milk sugar) to make ATP energy for themselves: a by-product of this process is lactic acid. LAB can be split into two groups: mesophilic LAB, which thrive at ~25–30˚C, and thermophilic LAB, which thrive at higher temperatures, ~38–45˚C. Thermophilic LAB are used typically to make yoghurt, whereas butter is typically made with mesophilic LAB. Some common LAB starter types used in butter-making are given in Figure 1.

Figure 1. Classification of lactic acid bacteria commonly used in culturing butter and yoghurt

Figure 1. Classification of lactic acid bacteria commonly used in culturing butter and yoghurt

The project

As the first step of the project, I wanted to create a flavoursome ‘base’ butter that we could use as the starting point for making the aged butters that I’ll discuss in Part 4.

Having read about chefs at Atera, NYC, making butter cultured with rinds of washed-rind cheeses (Josh tried it made with ‘Arpeggio’), and Patrik, the Butterviking, making butter with cream cultured by having the chefs at Noma dunk their hands in it, I was interested in exploring butters cultured using unconventional sources of LAB.


A few months before I arrived at the lab, Edith had done a project on Finnish viili, a yoghurt-like substance, often described as “ropey milk”, that is produced by a colony of symbiotic microbes (just like kefir and kombucha).

While variations between different viili cultures almost certainly exist, in general they are said to contain Lactococcus lactis subsp. cremoris, Lactococcus lactis subsp. lactis biovar. diacetylactis, and Leuconostoc mesenteroides subsp. cremoris. It is the latter, which produces exopolysaccharides such as dextran, that is the source of the slimy texture of viili and other similarly ropey fermented foods.

As can be seen from Figure 1, with these three bacteria present, viili is very similar to a mesophilic LD-type starter, but without Lactococcus lactis subsp. lactis. That is, it is very similar to many starter cultures that are used to make cultured butter.  

Viili also contains Geotrichum candidum, a fungus found on many bloomy-rind cheeses, most famously Camembert, and which gives viili its characteristic white, velvety surface. Meanwhile, on the surface of fruits and vegetables such as peach, nectarine, tomato, carrot and lemon, Geotrichum candidum can also cause Sour Rot leading to slimy secretions, also from the production of exopolysaccharides. But we’re more interested in the former.

Figure 2. Viili.

Figure 2. Viili.

Figure 3. Viili surface with Geotrichum candidum

Figure 3. Viili surface with Geotrichum candidum

Viili butter

With the addition of a few rounds of fresh milk, I was able to nurse Edith’s viili cultures back to full strength within a week, and used them to inoculate some cream. The butter I made with the viili-cultured cream was buttery, but tasted slightly musty, like old hay: not so good.

Furthermore, after 48 hours, the pH was only ~5.1 and it lacked the characteristic tang of a really good butter: it was clear that we needed to adjust the LAB in order to make the cream more acidic. This was important not just for taste but also for safety: culturing cream to a pH of ~4.2–4.5 ensures that it is inhospitable to pathogenic microbes.

Our approach was to complement the viili by adding lactic acid-producing LAB commonly used in beer-making. We already had samples of these in the lab (because of previous brewing projects) and they were particularly well-suited to our aims because they are commercially available in monocultures and can be stored stably for quite a long time.

The beer-making LAB we used included: Pediococcus damnosus (sours and produces diacetyl); Lactobacillus delbrueckii (produces moderate acidity and sour flavours found in lambics, Berliner Weiss, sour brown ale and gueuze); and Lactobacillus brevis (typically produces more lactic acid than L. delbrueckii). Though L. brevis is found in some cultured butters, it is not one of the most commonly used LAB, despite its ability to produce significant amounts of diacetyl [2]. 

In combination with the viili, the L. delbrueckii produced great cream and butter, but the L. brevis produced even better results (richer, more buttery). In contrast, the P. damnosus produced cream that had an unpleasant bready, yeasty aroma and did not acidify to a safe level. I also tried culturing cream with only L. brevis (i.e. no viili), but this produced a cream that was bitter, cheesy and tasted slightly of toasted rice: it was the LAB and fungus in the viili in combination with the extra kick of acidity provided by the L. brevis that gave rise to the best possible butter from our tests. 

A brief digression on Lactobacillus brevis

Like many bacteria, L. brevis has a multitude of uses:
- It’s found in pickles and kefir
- It’s used in beer-making, but an abundance of it leads to spoilage
- It’s found in the microbiome of healthy oral cavities [3], vaginas [4] and faeces [5] of humans
- Its ingestion has been shown to improve human immune function [6]
- Multiple strains have been patented for use in various novel technologies, often in probiotic systems [7]


Figure 4. Lower left: Viili/brevis butter; Upper left: Villi/brevis butter, ‘underchurned’, à la Butterviking's Virgin Butter; Right: Caraway and cascara butter

Figure 4. Lower left: Viili/brevis butter; Upper left: Villi/brevis butter, ‘underchurned’, à la Butterviking's Virgin Butter; Right: Caraway and cascara butter

Basic butter: viili + L. brevis

500 g pasteurised, unhomogenised cream (Naturmælk’s 38% piskefløde, pH 6.9)
5 ml Lactobacillus brevis culture (White Labs WLP672)
20 g viili starter

1. Mix ingredients in a sterile container. Leave at room temperature for 48 hours. The final pH should be ~4.5, and the temperature of the cream should be stable at ~24˚C throughout.)
2. Churn in a stand mixer with a dough hook until the butterfat and buttermilk separate. Pour off the buttermilk and save.
3. Work the remaining buttermilk out of the butter with a wooden spatula (a process known as ‘throwing’), washing periodically with fresh water.
4. Add salt to taste.

Yield: ~200g butter, ~250g of buttermilk.

The viili/brevis butter is intensely buttery, deeply creamy, tart and a little fudgey.


Caraway and Cascara Butter

Jason’s work on tea and coffee analogues and a chance encounter with Anette Moldvaer from Square Mile Coffee led to us receiving some bags of cascara (thanks Anette!). Cascara are the dried skins of coffee cherries, a by-product of coffee bean production. In addition to brewing tea with them, we noted that their flavour complimented that of caraway, a member of the Apiaceae family (carrot, celery, parsley) that is native to Europe, north Africa and western Asia, and which has long been used as a primary flavouring in Scandinavian Akvavit.

20 g roasted cascara (Los Alpes Cascara, produced by Aida Batlle in El Salvador)
10 g caraway seed

1. Lightly toast the caraway and cascara in a pan. Blitz to a fine crumb in a food processor; mix into the 'basic' butter during step 3.
2. Add salt to taste.

Serve on sourdough (esp. if you have access to that of Jonas Astrup Pedersen) or with grilled fish.

Figure 5. Cascara

Figure 5. Cascara

Figure 6. Cascara tea

Figure 6. Cascara tea

Clarified Crab Butter

Curious things often get brought to the lab. During my stay, as part of a project on Round Goby, (a fish invasive to Denmark, for which there are limited culinary uses; the fish are small, bony and not that flavoursome), we received delivery of a crate of Carcinus maenas (aka European green crab or shore crab). Carcinus maenas are also small with little meat to them, and are, as such, unprofitable by-catch for many Danish fisherman. Furthermore, they are invasive to the US and parts of Australia where they have a dramatically negative impact on other species, particularly smaller shore crabs, clams, and small oysters [8]. 

I made a butter by boiling my cultured cream with the crabs, before churning it. The results were quite fascinating: everyone who tasted it blind said it reminded them of brioche or pastry dough, but with some additional x-factor that they couldn’t quite place. 

The boiling of the cream is almost certainly where some of the "pastry dough" notes came from: essentially by boiling the cream we'd caramelised some of the milk sugars in the cream. 

500g cultured cream as per basic butter
500-750g of Carcinus maenas (European Green crab)

1. Freeze crabs.
2. Blanch in briskly boiling water for 3 minutes
3. Drain crabs and add to cream: bring to a gentle boil and simmer for 30 minutes. Skim off any scum and skin that forms.
4. Discard crabs and retain cream.
5. Chill the cream to 10ºC. Then churn. Add salt to taste.

Figure 7. Crabs

Figure 7. Crabs

Figure 8. Crabs 'n' cream

Figure 8. Crabs 'n' cream

A selected history of my many failures:

–Cheese-rind cultured butters made using various Nordic cheeses including the Danish Thise Mejeri Thybo Ost and Hodde Kristian Øko, and the Swedish Jürss Mejeri Granbarksost. These fermentations were difficult to control and produced some very funky, tangy, potent results. I didn’t produce anything I was happy with but I think this approach is worth pursuing further and could produce some truly extraordinary results. 

–Cream cultured with bee bread, which typically contains many LAB strains. Some of the creams developed floral and fruity (pineapple) notes but did not thicken or reach a satisfactorily low pH. Perhaps this particular bee bread had lost some of its culturing potency in storage? Definitely worth trying further with some fresh bee bread.

–Inoculated butters: I tried to grow moulds (Aspergillus niger, Penicillium camemberti) and bacteria (L. brevis) on the outer surfaces of butter pats in a process analogous to how bloomy-rind and washed-rind cheeses are made. However, my efforts were not successful, probably because there was insufficient water in the butter matrix (butter typically contains less water than cheese) and/or insufficient protein (butter contains very little protein, in contrast to cheese) to nourish the moulds. However, microbial growth might perhaps be achieved if the surfaces were washed once (or multiple times for Brevibacterium linens, one of the quintessential cultures of washed-rind cheeses) with buttermilk, which contains both water and all the milk proteins that don't make it into butter—an idea for further experiments.

Figure 9. Mould failing to grow on the surface of butter.

Figure 9. Mould failing to grow on the surface of butter.

Coming up: With a great-tasting ‘basic’ butter to use as a starting point, I began exploring if we could develop desirable flavour profiles from controlling the aging conditions of butter. 


[1] European Food Information Council (1999),

[2] Christensen, MD., & Pederson, CS. (1958). Factors affecting diacetyl production by lactic acid bacteria. Applied Microbiology, 6(5), 319–322.

[3] Walter, J. (2008). Ecological role of Lactobacilli in the gastrointestinal tract: implications for fundamental and biomedical research. Appl. Environ. Microbiol. 74(16), 4985–4996.

[4] Vásquez, A., et al. (2002). Vaginal Lactobacillus flora of healthy Swedish women. Journal of Clinical Microbiology. 40(8), 2746–2749. 

[5] Wilson, M. (2005). Microbial inhabitants of humans: Their ecology and role in health and disease. Cambridge University Press. 398.

[6] Kishi, A. et al. (1996). Effect of the oral administration of Lactobacillus brevis subsp. coagulans on interferon-alpha producing capacity in humans. Journal of the American College of Nutrition. 15(4), 408–412

[7] Castellana, JP. (2015). Probiotic composition for oral health. USPTO Applicaton #20150273000 A1. (Also, see

[8] Washington Department of Fish and Wildlife Conservation,

Aged Butter part 2: the science of rancidity

Added on by Johnny Drain.

by Johnny Drain

This series is about oxidation, rancidity, and aging butter. In Part 1 I gave some background about butter, rancidity and the cultural context for eating aged butter. In this second part, I’ll explore the science of oxidation in fats and the safety of eating them. I’ll then describe the results of my work on culturing butters with unusual sources of bacteria in Part 3 and on aging butters in Part 4.

In Part 1 of this series, we examined how rancidity, culturally speaking, is rather poorly defined: foodstuffs can be seen as rancid depending on historical precedent and context, even though they may involve similar or identical chemical processes in foodstuffs we regard as delicious. From a scientific perspective, rancidity can be defined a little more strictly, though we will see that discussing the science of rancidity, oxidation, and their relationship to each other can still become unclear. In this post, I will outline some of what we know of the science behind rancidity in fats and examine whether such fats are safe, and indeed where they already enter our diet.

‘Rancidification’ can be broadly defined as the development via chemical transformations of new, sensory-active, often hedonically-negative compounds that don't play a significant role in a food product’s expected/desired sensory profile. More specifically, with respect to fats and oils, it refers to the decomposition of triglycerides by hydrolysis and/or oxidation into free fatty acids, which can then break down further into a wide array of flavourful compounds [1]. The majority of this second post will be devoted to digging into the technical details of this definition, which we can use to start to understand why old butter is deemed ‘rancid’ but blue cheese is not, even though the same chemical processes may have taken place in both.

In rancid fats, the characteristic tastes and smells come primarily from the short- and medium-chained free fatty acids, whose carbon chains contain 12 or fewer carbon atoms (those with more are generally tasteless). Of these, the acrid-tasting, sweet- and goaty-smelling butyric acid (CH3CH2CH2-COOH, i.e. 4-carbon free fatty acid) is the primary culprit (Figure 1). In small quantities it can make positive contributions to flavour profile—it is found in sheep, goats and buffalo milk, Parmesan and mozzarella, and kombucha—but in larger concentrations is offensive: it can be used to make stink bombs and is the primary smell in human vomit.

Figure 1: Short- and medium-chain saturated fatty acids.

Figure 1: Short- and medium-chain saturated fatty acids.

Around 4% of fresh butter is made of a triglyceride of butyric acid, and when this breaks down the butyric acid is liberated and we can smell its sickly, caprine smell. Other responsible free fatty acids include caproic acid (6 carbons), caprylic acid (10), and capric acid (12)(Figure 1). The shared goat-related Latin stem gives you an idea of what they smell like!

Other compounds that contribute to rancid flavours in degraded fats include acetic acid, peroxides, alcohols, aldehydes and ketones. There are three main pathways responsible for the breakdown of fats and for the formation of these compounds that contribute to rancid flavours. Their principal mechanisms are well-characterised, although their precise effect on flavour are still not fully understood.


The most important rancidity reaction pathway in butter is oxidation (Figure 2). Oxidation of fat involves cascades of free radical reactions that cause the C-C double bonds of unsaturated fatty acids to break. This releases peroxides as primary reaction products, and subsequently alcohols, aldehydes and ketones, as secondary reaction products, which can then degrade further into various volatile products. The primary oxidation products have little or no effect on taste and smell, but the subsequent reaction products do. Oxidation reactions can be initiated by oxygen in the air or light (photo-oxidation), and are catalysed by metals; they are chain reactions that can propagate in the dark once started—so butter can turn rancid even if stored in the fridge or a cloche, if it has been previously exposed to light or oxygen.

Figure 2: Schematic of a lipid oxidation chain reaction.

Figure 2: Schematic of a lipid oxidation chain reaction.


The second critical reaction pathway that causes the degradation of fats involves hydrolysis by water and heat of the -O-alkyl ester bonds of a triglyceride to liberate free fatty acids, such as butyric acid, from the glycerol backbone (Figure 3). Polymerisation of the free fatty acids can then lead to the gummy deposits found on utensils used to store or cook with used cooking oil.

Figure 3: Schematic of the hydrolysis of a triglyceride. The free fatty acids can then break down.

Figure 3: Schematic of the hydrolysis of a triglyceride. The free fatty acids can then break down.

Enzymatic lipolysis

Spoilage of fats can also be caused by microbes, or certain enzymes—lipases—they produce. As mentioned in Part 1, many of the compounds found in rancid fats, and the processes that form them, are critical to flavour development in aged cheeses. For example, moulds that are introduced to blue cheeses, such as Penicillium roquefortii in Roquefort, produce lipases that break down triglycerides via hydrolytic reactions to create short-chain fatty acids, leading to spicy and peppery flavours. Enzymatic lipolysis also plays a key role in flavour development of hard cheeses such as Fiore Sardo and Pecorino, in which the lipase comes from the rennet paste used to initially coagulate them [2]. At this point, it’s probably also worthwhile dwelling on the primary chemical difference between cheese and butter: cheeses contain significant amounts of protein, whereas butters don’t. Therefore, proteolysis (the breakdown of milk proteins such as casein into amino acids and then volatile compounds) is a significant flavour formation pathway in cheese, but not in butter.


Now that we have established the chemical processes that can lead to rancidity, it is worth returning to the issue of terminology, specifically the distinction between the words ‘rancid’ and ‘oxidised’.

The first issue is that, in common parlance, they are sometimes used interchangeably. This conflation is not wholly incorrect: it is possible to have rancid fats that have been degraded entirely by oxidative processes, and to have oxidised fats that are rancid. However, this is not always the case: it is possible to have a fat that is rancid but that has not been oxidised (if it was degraded purely via hydrolysis), and to have a fat that is oxidised but not generally deemed ‘rancid’ (if only primary oxidation products, which one cannot taste or smell, have been produced, or, for example, as was highlighted in Part 1 in cases of chocolate- and toffee-making, if the oxidation leads to added desirable complexity of a flavour profile).

The second issue is whether positive or negative attributes can or should be ascribed to either of the two terms. In common and scientific parlance, both ‘rancid’ and ‘oxidised’ typically have mostly negative connotations, but long-standing examples can be found where they are used to express a desirable, positive character (most notably in the world of wine—’rancio’ with respect to e.g. sherries and cognacs, and ‘oxidised’ with respect to many natural wines).

To make sense of this blurry field, the key point to grasp is that the two words describe processes and properties that are non-binary. Many archetypally 'rancid'  and ‘oxidised’ flavour compounds make important, hedonically positive contributions to flavour profiles in quantities below some (ill-defined, contextual) threshold, e.g. 3% butyric acid in fresh butter. It's only if they are produced in larger quantities, that we might in common speech start terming the product in which they are found as 'rancid' or ‘oxidised’. (As an aside here, it is interesting to note that the descriptor 'oxidised' has entered, to some extent, the popular vernacular but the descriptor 'hydrolysed' has not and remains the preserve of the world of science.)

It’s not easy to distill the complexity with which these terms are used and understood into something simple, but we’ve devised a Venn diagram-like framework, shown in Figure 4, to try to clarify their interrelations. This diagram also helps to clarify the central concept behind the project: can we create a butter analogue of blue cheese, ‘blue butter’, which uses oxidation and/or hydrolysis to develop flavours that are a) intended/expected/desired and, therefore, b) not perceived as ‘rancid’ or ‘unpleasant’.

Figure 4: Framework for understanding the complex interplay between oxidation, hydrolysis and ‘rancidity’, in both scientific and more general contexts.

Figure 4: Framework for understanding the complex interplay between oxidation, hydrolysis and ‘rancidity’, in both scientific and more general contexts.

Factors affecting rancidity

The proneness of butter to turn rancid is dependent on what the butter is made of, how it has been made and how it is stored. The variables include: exposure to oxygen, light, and heat; the presence of antioxidants, microbes, and catalysts (e.g. metals such as iron and copper, which kitchen implements might be made of); the water and salt content of the butter; and the saturation of the fats in the butter.

For example, the oxygen in semi-solid room-temperature butter can move through the butter more freely (has higher mobility) than in colder, more solid butter: room temperature butter will therefore, all else being equal, oxidise more quickly than refrigerated butter. Furthermore, butters with higher concentrations of water can spoil more quickly, predominantly because free metal ions in the water can catalyse oxidation reactions [3].

Conversely, butters with a higher level of saturated fats will be more stable with respect to rancidification. Similarly, butters that contain more antioxidants—occurring naturally in the diet of the cows or added at some point during processing—remain stable for longer.

Antioxidants typically scavenge oxygen by being sacrificially oxidised, thus preventing the formation of primary oxidation products. Once antioxidants are exhausted, the level of primary oxidation products increases. However, these are not detectable to the human palate. Therefore, how quickly something turns rancid can be deceptive. For example, two samples, one with a much higher concentration of primary oxidation products, may taste, look and smell the same. It has also been found that some antioxidants—most notably for this project, some species of seaweeds found on the Danish coast—serve the extra function of actually reducing secondary oxidation products to their original oxidation states [4].

Modern manufacturing processes for many foods involve addition of a panoply of synthetic antioxidants, each with various strengths and weaknesses: some common ones include propyl gallate, BHA and BHT. However, traditionally, many naturally occurring antioxidants have been used to preserve fats. For example, studding a ham with cloves, which contain antioxidative phenolic compounds, serves to add flavour but also protect its fats from free radical oxidation; and slippery elm bark has been used to preserve bear fat [5]. Furthermore, oats—a good source of phenolics— might serve an antioxidative effect in the double cream cheese Caboc (reputedly Scotland’s oldest cheese, dating from the 15th Century), which is rolled in toasted oats.

With the advent of more rapid processing and distribution methods, modern butters and oils typically reach consumers in a less oxidised state and/or with more antioxidants intact. For example, in many places olives were traditionally harvested in batches and stored, perhaps even for months, until enough had been collected to press [6]. As a result, oxidation and fermentation would take place, and polyphenolic compounds, which impart the oil with spiciness and bitterness, would be sacrificially consumed. (Leaving them to rot slightly was also said to facilitate extraction of the oil, leading to greater yields.) The resulting oil would be milder and smoother than the ones that are made today, in which olives tend to go from tree to oil in under 12–24 hours.

Is eating ‘rancid’ or oxidised fats bad for you?

There have been a number of alarming claims about the harmfulness of rancid fats, linking them to, among other things, cancers.

However, much of the research we found cited alongside such claims has been extrapolated or is only tangentially relevant, e.g. experiments performed on animals in which, in order to produce measurable levels of adverse effects, much larger amounts (in relation to body weight and lifespan) than would be encountered by humans were used. Food: The Chemistry of Its Components highlights this fact, and adds that “the possibility that lipid oxidation products are toxic to humans remains unresolved” and “[despite claims to the contrary] there is little evidence at the present time to suggest that oxidized fats do cause cancer in humans.”[7]

Furthermore, McGee’s On Food and Cooking reassures us that “rancid fat won’t necessarily make us sick, but it’s unpleasant”, [8] and, as mentioned, the processes through which we make some cheeses, and the compounds these processes produce, are analogous to those that cause rancidity in fats.

Therefore, in essence, the answer to the question is: no, not in the amounts one might typically consume them as part of a balanced diet.

Figure 5: Photograph of the telltale translucent layer that develops on the periphery of slightly rancid butter.

Figure 5: Photograph of the telltale translucent layer that develops on the periphery of slightly rancid butter.


Given that the chemical processes responsible for rancidity in butter, and the flavours and aroma compounds they produce, are common to and characterise many much-loved cheeses, and that, furthermore, the perception of rancidity and oxidation in foods and fats are culturally elastic and context-dependent, the central hypothesis of this research was that we could make butter in which some mildly ‘rancid’ character added richness and complexity to its flavours, thus enhancing its gastronomic qualities, uses and value.

For example, could we prioritise one rancidity pathway over others to produce a desired flavour profile? Could we stabilise a mildly rancid butter in a given state using an appropriate combination of antioxidants or storage conditions? Taking inspiration from existing products—such as Morocco’s aged smen and blue cheeses that undergo significant lipolytic flavour development—could we reframe rancidity in butter as a positive quality?

In the next two instalments I’ll detail the results from our tests that explored whether this was indeed possible: this involved heaps of bacteria sourced from unusual places, an interminable obsession with pH readings, and a lot of cream.



[1] Allen JC. & Hamilton RJ. (1994). Rancidity in foods. London: Blackie Academic.

[2] Fox, PF. (2004). Cheese: Chemistry, physics and microbiology: Volume 1: General aspects, Elsevier: Academic Press. 60

[3] Saxby MJ. (1996) Food taints and off-flavours. Boston, MA: Springer US. 176.

[4] Farvin KS. & Jacobsen C. (2013). Phenolic compounds and antioxidant activities of selected species of seaweeds from Danish coast. Food Chemistry. 138(2-3), 1670–81.

[5] Min DB. & Smouse TH. (1985). Flavor chemistry of fats and oils. Champaign, IL: American Oil Chemists' Society. 155.

[6] Vossen, P. (2007). Olive oil: History, production, and characteristics of the world's classic oils, Hort. Science, 42(5), 1093–1100.

[7] Coulate TP & Blumenthal H. (2009). Food: The chemistry of its components. Cambridge, UK: Royal Society of Chemistry. 122–123.

              [8] McGee H. 2004. On Food and Cooking: the Science and Lore of the Kitchen. New York: Scribner. 204.





Aged Butter part 1: background and basics

Added on by Johnny Drain.

by Johnny Drain

This series is about oxidation, rancidity, and making aged butter. In this first part, I'll give some background about butter, rancidity, and the cultural context for eating aged butter. In the second part, I’ll explore the science of oxidation in fats and the safety of eating them. I’ll then describe the results of my work on culturing butters with unusual sources of bacteria in Part 3 and on aging butters in Part 4.

Butter. A symbol of purity in India and of depravity in the hands of, amongst other things, Marlon Brando.

Butter is a vector for taste. It carries fat-soluble flavour and odour compounds and therefore facilitates the expression of non-water-soluble flavours and aromas, such as of spices and herbs, in our food. In this role it is a workhorse of many classical canons of cookery, most notably that of France.

It’s also delicious as a primary, characteristic flavour in its own right: cultured butter, made by culturing cream with lactic acid bacteria prior to churning, has a gently refreshing acidity and rich, well, butteriness.

The Project

My project at the lab focused on butter, but not normal butter: aged butter. I started thinking about this when I made a salted caramel with butter that had been kicking around my fridge for a little too long. The outer surface had yellowed and it smelled slightly sweet and a little goat-like, but I thought it probably wouldn’t affect the flavour of the caramel. I was wrong. The caramel was very tasty, but with some unusual, subtle, savoury, meaty notes (step aside bacon jam).

Most people, including myself, would find the idea of eating ‘rancid’ butter stomach turning. However, as I dug into what rancidity was, and whether it is even okay to eat old butter, I found a 2011 study by sensory scientists at UC Davis [1] that found that 44% of tasters preferred olive oils with some degree of rancidity, and, furthermore, that one of the compounds found most prominently in rancid butter—butyric acid—is also found in significant amounts in sheep and buffalo milk, and a wide range of cheeses, including Roquefort, Limburger and Gruyère [2].

Similarly, American peanut butter, which contains rancidity-prone polyunsaturated fats, can taste rancid to non-Americans; yet the US is said to spend a whopping $800 million a year on the stuff. “In some cases, we [Americans] have gotten used to rancid flavours," says food science writer Harold McGee, "so we assume that they are normal."[3]

So perhaps, I thought, many people’s attitudes to certain funky, mildly rancid flavours are unnecessarily negative? Maybe there is scope for making butters with some controlled degree of rancidity, to develop and accentuate certain desirable flavours?

Conscious that this might be a hard sell for even (or perhaps especially) the most ardent of butter lovers, I was heartened to find that precedents do exist—some cultures like aged flavours in fats and have developed culinary uses for them.

In Morocco, highly-prized ‘smen’—or as it is sneeringly called in French, beurre rance—is made by mixing normal butter with herb-infused water (often with oregano), leaving it overnight, straining, and then aging for anywhere between a couple of months and several decades. It has a texture similar to that of normal butter but tastes like a spicy blue-cheese or Parmesan rind. The oft-recounted story is that families would make a batch of smen on the day their daughter was born, and only open it to stir through the ceremonial couscous on the day of her wedding. It is also known as a signifier of wealth, with reports of royalty hoarding smen [4]. From my own trials, roasting chickens in it and adding some to stews or stocks (indeed, as is often done with parmesan rind) also works wonders: it adds a rich, unique complex flavour that would be difficult to attain with any other combination of ingredients.

Mounds of glorious smen in a Marrakech souk.

Mounds of glorious smen in a Marrakech souk.

It is also of note that Yak’s butter, which forms a central part of the Tibetan diet in butter tea and tsampa dumplings, is often described by westerners as tasting ‘rancid’, and that slight rancidity is part of the flavour of traditional confit [5]. Perhaps the closest northern European analogue to smen is bog butter—butter packed into barrels and buried in peat bogs, a tradition known in Scotland, Ireland and Scandinavia, but which seems to have died out before the 19th century—despite the fact that the acidic, anoxic environment of the bog actually prevents, or at least dramatically slows, oxidation and degradation of the butter. 

Looking for more contemporary examples, since starting the project I found that Zak Pelaccio from Restaurant Fish and Game in the Hudson Valley, NY, ages butter brushed with local whiskey and wrapped in horseradish or turmeric leaves, so it takes on a gaminess and sherry-like nuttiness, and then whips it with fresh yoghurt. Furthermore, Matt Lightner from Atera in New York ages butter made from cream cultured with cheese rind for a week at room temperature.

So, while examples of aged butters can be found throughout the world, they have limited notoriety, popularity and availability. In marked contrast, cheeses such as Gorgonzola, Roquefort and Stilton [6], in which some of the key flavour compounds—and the processes that create them (such as the transformation of fatty acids into methyl ketones)—are the same as in rancid butter, are gastronomically prized and appreciated across the globe.

My project therefore aimed to explore what we really mean by rancidity, from a chemical and cultural perspective, why old butter seems to have developed such a bad rep whereas cheeses with similar compositions are celebrated, and, ultimately, whether mild, controlled rancidity in butter can be a positive hedonic quality.

Butter Basics

First, a little overview of what butter is. Its composition is normally a minimum of 80% fat, 15–17% water, and 1–2% other stuff—non-fat milk solids—which includes milk proteins, phospholipids, free fatty acids, calcium, fat-soluble vitamins (A, D and E), and fat-soluble pigments such as carotenoids that give butter their colour. The more carotenoids, the more yellow the butter; goats milk contains few carotenoids and is therefore much paler than that of cows. Butter contains only small traces of lactose so, like many cheeses, it’s suitable for lactose intolerants, but people allergic to milk proteins should avoid both.

Cream, the precursor to butter, is an oil-in-water emulsion. Churning damages the protective layer of phospholipids and milk proteins that cover the fat globules, and which normally prevents them from coagulating. With these protective layers broken, the fat globules coalesce into a solid mass—butter, a water-in-oil emulsion.

Freshly churned butter. The milky droplets are buttermilk, the liquid that remains once the butterfat has coagulated.

Freshly churned butter. The milky droplets are buttermilk, the liquid that remains once the butterfat has coagulated.

The fat in butter (and milk) is composed primarily of triglycerides. Triglycerides are shaped a bit like the letter ‘E’ (Figure 1). They have a backbone of a glycerol unit, with one fatty acid chain bonded to each of its three oxygen atoms—this arrangement of bonds make it what chemists call an ester, or more specifically a triester. Triglycerides are the central component in vegetable oils and animal fats [7], and are also found in human skin oils [8].

In all triglycerides, the glycerol backbone is always the same, but the length and composition of the chains dictate the properties of the fat. The fatty acid chains are made of links of either single or double carbon-carbon bonds. When all these bonds are single carbon-carbon bonds we call the chain saturated, but if there are one or more carbon-carbon double bonds we say it is unsaturated.

Figure 1. Short- and medium-chain saturated fatty acids.

Figure 1. Short- and medium-chain saturated fatty acids.

Fats with more unsaturated triglycerides, such as vegetable oils, tend to be softer, while those with more saturated triglycerides tend to be firmer. Butter is mostly saturated triglycerides and is therefore solid at room temperature. Importantly, unsaturated fats are more prone to rancidity than saturated ones, hence butter is more resistant to rancidity than, say, soy or sunflower oil. (‘Trans-fats’ refer to the stereochemistry of unsaturated fats, but we won’t be going into that here.)

If the bonds between the fatty acid chains and the glycerol backbone break, this liberates ‘free‘ fatty acids, which are key to the development flavours ('good' and 'bad') in fats. But I’m getting ahead of myself, more on that in Part 2.

A Short History of Butter Making

The word butter comes from the Latin butyrum, which in turn comes from the Greek bouturon (where bous means ‘grazing ox’ and turos means ‘cheese’) [9]. However, its manufacture, with sheep and goats’ milk rather than cows, can be traced back 4,000 years, meaning it predates olive oil.

Like many of the foods we eat, butter likely started off as a way to preserve nutrients—in this case, by extending the shelf life of milk in a rich, delicious, energy-dense way. Northern Europe, with its combination of pastures for livestock and cool climates, was perfect for butter, but in the hotter climes of southern Europe, butter spoils more quickly than cheese. Perhaps for this reason, the Greeks and Romans were a little snooty about the stuff and considered it to be food for northern barbarians. Greek comic poet Anaxandrides referred to Thracians as boutyrophagoi or “butter-eaters” (admittedly, other scholars said far meaner things about them), while Pliny the Elder, in his Natural History, calls butter “the most delicate of food among barbarous nations”, and then proceeds to describe its medicinal properties. Interestingly, Galen described butter purely as a medicinal agent rather than as a food—a notoriously tricky distinction best left for another time, but suffice it here to say the awareness that butter is good for you is millennia-old.

Introduction to rancidity and oxidation:

One of the central questions of the project was: what do we mean by ‘rancid’? As I explored this, I realised that there are in essence two relevant meanings—a more scientific one and a more cultural one. The two are not well correlated, and there lacks, among the general populace, including myself and most of us at the lab, a coherent lexicon to describe the latter.

Something rancid is typically defined as smelling or tasting unpleasant as a result of being old and stale, which is of course incredibly subjective: when we describe something as rancid what we often mean is “this tastes too old/weird for me” or “I am not willing to eat this”.

Context is a critical factor in determining what we think is palatable. I’ve discussed some examples of rancid butters above but, more widely, encouraging rancidity is actually not such a crazy idea: Cognac and Armagnac are both aged to develop ‘rancio’ character, which derives from oxidative processes [10]; in the UK, butter for toffee was often stored to develop some rancidity, to produce a more desirable stronger dairy flavour; and in the USA, chocolate manufacturers encourage their milk fat to undergo some rancidification by fat-digesting enzymes to develop modest cheesy and animal notes which enhance the complexity of the chocolate’s flavour [11]. In analogous processes, the enjoyment of many nuts is augmented by roasting-induced lipid oxidation, which cause the development of new flavours [12], and highly prized Sherry, Marsala, Vin Jaune, Maury, Banyul and Madeira wines rely on flavour development via oxidative processes [13]. In particular, because Madeira wines are so oxidised there is little scope for further oxidation and they are very stable, meaning that they can be stored for many years before being enjoyed.

In all these cases, particular audiences of people enjoy the results of ‘rancidity’—the flavours and value it adds to a product—without thinking of it as such. Furthermore, despite the words ‘rancid’ and ‘oxidised’ being more typically used in general parlance to imply negative hedonic qualities, there are also cases (eg. ‘rancio’ and ‘oxidised’ in the context of some wines and spirits) where the same words are used to describe positive attributes. Nonetheless, my experience of explaining to people the concept of this project showed me that phrases like ‘rancid butter’ and ‘oxidised fats’ do typically elicit a pained expression, and a sudden unwillingness to let me cook for them. So, if we want to develop a delicious, mildly oxidised, hedonically-positive butter—which has a flavour profile similar to cheeses that we know people love—then perhaps the first step should be simply to not describe it as ‘rancid’, or even the somewhat more technical-sounding but not entirely neutral ‘oxidised’ (more on the intricate chemical and linguistic relationships between ‘rancidity’ and ‘oxidation’ in Part 2). We could instead, for example, use the term ‘aged’ to draw parallels with the worlds of cheese and wine, where instances of similar physico-chemical processes elicit positive hedonic response. 

Additionally, cultural priming is important, and people from different cultures have very different levels of sensitivity to rancidity. We have seen how Moroccans prize smen, yet for their French colonisers beurre rance was barbaric, offensive stuff. Roland Barthes, no less, writes on the subject:

"One day I was invited to eat a couscous with rancid butter; the rancid butter was customary; in certain regions it is an integral part of the couscous code. However, be it prejudice, or unfamiliarity, or digestive intolerance, I don’t like rancidity. What to do? Eat it, of course, so as not to offend my host, but gingerly, in order not to offend the conscience of my disgust…"[14]

Barthes raises the notion of disgust which is key to understanding what rancidity is, and isn’t. As Rozin and Fallon note, "It is the subject's conception of the object, rather than the sensory properties of the object, that primarily determines the hedonic value."[15] Thus, disgusting foods need not even have negative sensory properties: many people find the idea of eating some animal species (rats! dogs! horses! snakes!) revolting, and yet, from a nutritional and sensory perspective, they are pretty similar to those that they are perfectly happy to eat (piglets, sheep, cows, geese). Put another way, even stuff that tastes good can be perceived as disgusting. Rozin expands:

"The sense of disgust that overwhelms someone who bites into a wormy apple—the feeling of revulsion, the spewing of chewed apple pieces, the approach to the brink of vomiting—is not brought on because the worm tastes bad. The half worm is 'found' by seeing it writhing in the bitten apple; it is not tasted at all."

Elicitors of disgust vary enormously from culture to culture, and to a lesser extent from individual to individual within cultures (with some possible exceptions, such as vomit and faeces, which may be universal disgust objects—though surprisingly there is limited evidence to support this notion) [16].

Some conjecture on cheese and butter

Pondering the relationship between cheese and butter, I became deeply interested in why rancid butter and blue cheese, for example, are regarded so differently. Why is there widespread cultural acceptance for one but not the other? Here are some ideas—granted, they are speculative.

DeLaval cream separator.

DeLaval cream separator.

Firstly, butter requires more raw ingredients. It takes 20 litres of milk to make 1 kg of butter, but only 10 litres to make 1 kg of hard cheese, and even less for softer cheeses: 1 kg of Brie might require 7 litres [17].

Secondly, the milk from which cheeses are made has long been readily available in significant amounts and people have had time to perfect strong-tasting, challenging varieties of cheese, and their appreciation has been firmly embedded in the cultures that produce or import them. In contrast, cream was historically very much a luxury and only available in smallish quantities until the late 19th century when mechanical cream separators were invented. Prior to this, using traditional shallow setting pans, which could only handle a modest amount of milk per batch, it would take 3 days to generate a small amount of cream. The method was time-consuming and unreliable; the cream could easily sour in the process. However, once De Laval invented his continuous cream separator in 1878, the cream could be separated from 150 kg milk in just one hour.

Thus, until relatively recently, making butter was more expensive and impractical than making cheese, meaning that the resulting product was more precious and valuable, and so people might have been less willing to let it age or develop unusual flavours and aromas. Without widespread cultural precedent for enjoying it—we have highlighted a few pockets of the world where the tradition did develop—aged butter seems to have been largely overlooked as a source of deliciousness, and rather become one of Rozin’s “objects of disgust”.

Compounding this issue could be the central role that butter plays in the classic French cooking that has exerted such strong influence over global gastronomy, and via a trickle-down effect to ordinary households in many regions, for such a long time. With France’s wealth of delicious, funky-tasting cheeses—which provide plenty of sources of goaty, meaty, methyl ketoney flavours—perhaps there was little motivation to explore the aging of butters to create new, alternative additional sources of these flavours, especially when butter was already in high demand, used in baking, basting, sauce-making and pastry, and being eaten as a condiment in its own right. Contrast this with Morocco, where butter plays a far less critical role in the cuisine and there is a notable lack of aged cheeses; the complex flavour profile that smen can add to a dish sits quite uniquely amongst other traditional foods of the region.

Stay tuned for Part 2 of this series, in which I will explore the science behind rancidity, what it means chemically and linguistically, and how safe it is to eat aged fats.

A sampling of various aged butter trials

A sampling of various aged butter trials


[1] Delgado, C. & Guinard, JX. (2011). Sensory properties of Californian and imported extra virgin olive oils. Journal of Food Science, 76(3), 170–176. 

[2] Fox, PF. (2004). Cheese: Chemistry, physics and microbiology: Volume 1: General aspects, Academic Press, 381–383.

[3] McGee H. (2015). Personal communication.

[4] Wolfert, P. (2012). The food of Morocco. A&C Black, 159.

[5] McGee, H. (2004). On food and cooking (ebook). James Bennett Pty Ltd, 253.

[6] Belitz, HD. & Grosch, W. (2013). Food chemistry. Springer Science & Business Media, 502.

[7] Nelson, DL. & Cox, MM. (2000). Lehninger principles of biochemistry (3rd Ed.). Worth Publishing. 

[8] Lampe, MA. et al. (1983). Human stratum corneum lipids: characterization and regional variations. J. Lipid Res., 24: 120–130.

[9] Morton, M. (2004). Cupboard love 2: A dictionary of culinary curiosities. Insomniac Press.

[10] McGee, H. (2004). On food and cooking (ebook). James Bennett Pty Ltd, 1112.

[11] McGee, H. (2004). On food and cooking (ebook). James Bennett Pty Ltd, 998 and 1020.

[12] Agila, A. & Barringer, S. (2012). Effect of roasting conditions on color and volatile profile including HMF level in sweet almonds (Prunus dulcis), Journal of Food Science, 77(4), 461–468.

[13] Robinson, J. & Harding, J. (2006). The Oxford companion to wine (3rd Ed.), Oxford University Press.

[14] Barthes, R. (1976). Sade/Fourier/Loyola, translated by Richard Miller, Hill and Wang.

[15] Fallon, AE. & Rozin, P. (1987). A perspective on disgust,  Psychological Review, 94(1), 23.

[16] Bitton, D., Current theories of sensory and interpersonal disgust.


Sex on the Beach

Added on by Josh Evans.

by Josh Evans and Guillemette Barthouil

It must have been in the spring of 2013 when one of our hunters, Jesper Shytte, brought on board a beast none of us had ever worked with in the kitchen. Late April and early May, he told us, was the best time to hunt beaver, and he had brought us one, along with its castor sac and a sample of castoreum tincture he had made.

The beaver tail, prior to cooking

The beaver tail, prior to cooking

We cooked the tail for staff meal (it takes some finesse, we later learned; Jesper has since offered to show us how) after immediately popping the castor sac into 70% ethanol to make tincture our own.

Castor tincture, day 0

Castor tincture, day 0

The sac

The sac

Castoreum is the secretion of the castor sacs of the Eurasian and North American beaver (Castor fiber and Castor canadensis, respectively), which they mix with urine to mark their territory. Beavers have been valued for centuries in Europe and North America for their pelts, their castor sacs, and their flesh. Castoreum has a particularly long history of use. It was used as a medicine at least as early as ancient Rome and as late as the early 20th century [1], and is still used today as a perfume and food additive for its notes of leather, vanilla, smoke, and musk. In fact, beaver became so popular that by the middle of the 19th century many European populations had been trapped to near extinction [2]. They then became protected in many areas of Europe to allow the populations to recover, and now, after around 150 years, the conservation has been a great success—the International Union for the Conservation of Nature's Red List now lists both species under the category of 'Least Concern'. Many populations have bounced back—in some places even becoming so populous that they are crowding out other species and are beginning to have some detrimental effects on forest and riparian landscapes. They are, after all, quite efficient tree-cutters and river-dammers. Many areas of middle and northern Sweden are just such places, which is where Jesper found himself that spring, hired to help keep certain overactive beaver populations 'in balance' with the local ecosystem (an idea which is of course also a contestable ideological position—that humans not only have access to knowledge about this ideal, singular, and stable 'state of balance', but that we also have the power to orchestrate it, with or without disinterest—the ultimate neoliberal 'Nature' [3]).

Wildlife emerges through ecologies of becomings, not fixed beings with movements of differing intensity, duration, and rhythm. Wildlife is discordant, with multiple stable states. It is not in any permanent balance. It is shaped by but divergent from the past, multinatural in its potential to become otherwise.
— Jamie Lorimer, Wildlife in the Anthropocene: Conservation after Nature

Hunting beavers is not yet allowed again in every member state of the EU, but in Sweden it is from the 1st of October to the 10th or 15th of May (the former in the south, the latter in the north). One may only hunt them with rifles [4]. 

Working with the beaver and its castoreum has fed into a larger ongoing conversation at the lab about humans' roles in ecosystems, and the different ways we participate in eroding, maintaining, and contributing to biodiversity—intentionally and not. Is it possible to use responsible, ecologically-attuned hunting as a way of participating in and contributing to flourishing ecosystems? If so, how? And how can we use taste and cooking as one way to give value and respect to the creatures we hunt and to ensure, for example, that nothing goes to waste? These are not new ideas by any means, but it is surprising how far some contemporary policy and public opinion has strayed from this idea. We think it is more than time to bring it back. For a conversation between Roberto and our hunter friend David Pedersen on the role of hunting and the hunter in contemporary eco-conservation, take a listen to our NFLR podcast 'Two white flies'.

Since starting that first tincture in 2013, the big glass jar of alcohol sat on one of our shelves, an inscrutable specimen slowly disappearing in a darkening veil of brown. We opened it up now and then, to smell the particular smell and keep it floating in our minds.

Jesper's tincture, and ours

Jesper's tincture, and ours

Finally, in June 2014, Guillemette and I decided it was time for something to be done. Given we already had the castor in alcohol, it seemed perfectly natural to follow that to its logical end and make a cocktail. We have been interested in tinctures and perfumery for some time, with Ben and Justine working on different techniques, so it seemed like a great way to incorporate some of these methods of aroma extraction, like enfleurage and absolutes, into a recipe. We had also learned the beavers use castoreum to attract mates, which echoes its use in perfumery as an attractive, musky base note. At last we had an excuse to make an NFL version of Sex on the Beach.

Starting our mixing experiments..

Starting our mixing experiments..

After a few very serious experimental trials, this is what we came up with.

Sex on the Beach, NFL-style

400 ml high-quality vodka
58 ml dulse snaps (we used one made by Schumacher Brændevin)
58 ml beach rose absolute
50 ml beach rose vinegar
Castor sac tincture

Beach rose absolute
Enfleurage. Mix 50g of cocoa fat powder with 10g of fresh unblemished beach rose petals. Replace petals with fresh ones every day for one week. Then wash the fat with a small amount of 70% ethanol to obtain the absolute.

Beach rose vinegar
50g rose beach petals
450g apple balsamic vinegar
Put the ingredients together in a vacuum bag and vacuum on full seal.

Mix first four ingredients together and store in a sealed glass bottle in the freezer.
Prepare glasses by frosting in the freezer (I believe the ideal shape may be a mini-coupe). Place glasses on the counter and, using an atomiser, spray the castoreum tincture once or twice over the glasses, so the vapour settles in and on the glasses. Then fill with desired amount of cocktail, straight from the freezer. Serve immediately.

We wanted to incorporate the beach rose in two different ways, to highlight how different methods can be used to extract different registers of aroma. The absolute uses neutral fat to absorb the lipid-soluble volatile molecules, which are then dissolved out of the fat with the ethanol wash. The vinegar, on the other hand, absorbs the water-soluble volatile molecules, which are then held in the acidic solution. We also made a cordial to investigate how sugar affects aroma extraction from the rose, but didn't end up using it—we had enough rose aroma and Guillemette and I like our cocktails spirit-forward and dry.

Aside from name, and perhaps the vodka, in no way does this recipe bear any resemblance to the actual cocktail. We'll let the community decide if this is a good or bad thing. 

Months after making this recipe, I learned that there is already a hunters' tradition in Sweden of making snaps with the castor sac, called bäverhojt in Swedish (lit. 'beaver shout'). There truly is nothing quite new under the sun...

Stay tuned for some further castoreum exploits...

The castor and its tincture, June 2015

The castor and its tincture, June 2015



1. British Pharmaceutical Codex, 2nd. ed. Pharmaceutical Society of Great Britain, 1911.

2. Parker & Rosell. 2003. Beaver management in Norway: a model for continental Europe?. Lutra 46(2): 223-234.

3. Lorimer, Jamie. 2012. Multinatural geographies for the Anthropocene. Progress in Human Geography 36(5): 593-612.  

4. 'Hunting in Sweden'. Handbook of Hunting in Europe, 1995. <>. Published online 2005. Accessed 2015.


Birch buds

Added on by Josh Evans.

by Josh Evans

It was in the heart of winter of 2013, just after solstice. Guillemette and I took up to Nordskot in Norway, above the Arctic Circle, to visit our supplier Roderick Sloan for the first time.

L to R: Guillemette; Pawel, Roddie's assistant; and Roddie.

L to R: Guillemette; Pawel, Roddie's assistant; and Roddie.

The sun would not rise, per se—more approach the horizon asymptotically from below, hover for a while under the glow, and descend again. There was, for a few hours if there was also luck, some light, and none of it direct.

Sometimes we used our brief day out on the water, checking sites, scouting new ones. Others we spent walking the wet heath, fishing with the kids at the fjord's inlet, and stumbling upon things surely known to others but not, at that time, to us.

The birch bud was the primary one.

Birch trees surround Roddie's property. As we walked through the brush we would absent-mindedly pick a twig, a leaf, or in this case, a bud so aromatic the resinous smear stayed on our fingers hours after crushing it.

This small discovery prompted a few sole-purpose excursions to pick as many as we could before our bare hands would refuse from the cold. The trees were mostly short and dense, which made them easy to pick from, and everywhere, which made it easy to not over-harvest from any one.

After picking, the best and easiest way we had to preserve their potency was to pound them with salt. This seemed to retain their powerful aroma and yielded a fine salt with a satisfying moist feel.

We returned to the lab in January excited with our find. It proved versatile.

Then, in April/May, Guillemette went up to Jämtland in Sweden to spend some weeks working with Peter Blombergsson—perhaps more popularly known as 'the Duck Man', through his relationship with Restaurant Fäviken—and his ducks. There, the birch buds had still not yet begun to open, and she managed to pick quite a good amount and this time put them into tincture.

We have noticed, while harvesting buds at different times and from a few different places, that the buds seem to be at their best—most aromatic and least bitter—deepest in winter and often further north, where and when the weather is coldest, long before any sign of spring begins the transformations that lead them to unfurl into new leaves.

Michael harvesting birch buds in Småland, Sweden, January 2015.

Michael harvesting birch buds in Småland, Sweden, January 2015.

After experimenting casually with the salt and tincture, we settled on a way to incorporate the sweet, heady aroma into a dish. We presented it with dessert at The Science of Taste Symposium at the Royal Danish Academy of Arts and Letters in August 2014: lemon verbena koldskål with freeze-dried berries, lemon thyme sugar, kammerjunkere, and the birch bud tincture vaporised over the tables as it was served.

This little gem continues to hang around the lab finding its way into different things, and it's about time to share it.

For more on birch, check out some of our other work with the sapbark, and the chaga fungus.

Artist-in-residence: mobile and mothership

Added on by Rosemary Liss.

by Rosemary Liss

As an artist my role at Nordic Food Lab was somewhat more fluid. Yet what began as a gentle anxiety—”what is my purpose? where do I belong?”—became the driver of my projects and interactions. I found a space between the experiential, the edible, and the data-driven. While my research took many directions, I also worked to create installation pieces for the space that manifested both the principles of the lab and my personal experience of it. 

I began to gather discarded materials: vegetable scraps, sauerkraut, kombucha mothers. Even within an organization that champions the latent possibilities of the unwanted we continue to accrue waste. But here lies more beauty—within this waste, other types of inedible yet aesthetic elements emerge. Texture, colour, form are still richly present. The building blocks of sculptural installations reached out to me.

I wanted to create work that spoke of these things: the interactions across disciplines, the hive mind working towards unknown goals, the nuances of the individual braided into a larger textile.

I dehydrated and saved it all. I created pieces like stained glass from ombré-hued kombucha mothers of rhubarb, cascara, elderflower. I laminated the dehydrated membranes then pieced them into a quilt. The fibres pushed tightly against the plastic-like embossed prints. I built a frame from scrap wood found behind a container city. Thinking about soft sculpture and the discourse between a range of materials I added felt corners and hung the frame with bright red thread. Gentle reminders that this space is not just a ‘lab’. Yes, we were once on a houseboat, but this textile piece speaks to the wunderkammer, the cabinet of curiosities that its inhabitants are creating. From meat curing in wax, to jars of insects and dehydrated frogs—there is nothing sterile about this place.

['mothership' photos by Chris Tonnesen]

Inspired by conversations about phylogenetic diagrams, recursive cycles, and the constraints of language, I made a mobile. I used dehydrated food waste, the weighted ornaments ranging in size and colour. Tomato pulp in cadmium red, creamy sauerkraut, plum and sencha greens, a spinning galaxy of vegetable paper. Hung from red thread the mobile gave a nod to its mothership, the quilt that now hung parallel along the ceiling, joining the kitchen and desk spaces.

[mobile photos by Chris Tonnesen]

Building these sculptures brought up questions about the importance of aesthetics when it comes to the complete sensory experience. The non-edible aspects of a space, a dish, or any experience not only inflect the edible but also form it. Our connection to food goes beyond taste and aroma. The senses are heightened or diminished by the visual, olfactory, and tactile. With multi-sensory perception in mind, I created an event around kombucha mother projections, curated sounds, and a variety of kombucha cocktails, sorbets, and gelatins. This culminating party allowed me to show my colleagues and friends what I had been working on over the previous three months, and the relationships between my work on kombucha mothers and the installations for the lab space. It brought together a mix of people from across the city, each bringing something unique into that vibrant night in our courtyard, lit with projected visuals, filled with dulcet sounds and the chatter of friends and strangers, and warmed with a reminder to soak it in and enjoy the surprises of the edible.

portrait of the artist.

portrait of the artist.

Artist-in-residence: Eating the zoogleal mat

Added on by Rosemary Liss.

by Rosemary Liss

This project was born out of a type of failure. The kombucha membrane is the perfect medium to tell this story. The look, the feel, colour, texture, flavour. I wanted to touch and taste. I found myself in a gelatinous substrate, a mother, a zoogleal mat. Suddenly I found a confluence of art and fermentation. I became obsessed.

Eating the SCOBY brought up rich and diverse imagery. Films where food stands in for sex: that scene in Tampopo where a mobster and his moll pass a raw egg yolk back and forth with their tongues in coital bliss; MFK Fisher’s budding sexuality conveyed in eating her first oyster. I find this appealing, some find this disgusting. Taste happens.

With these tropes in mind, I drafted some dishes using the mother. I paired SCOBYs with salt, cream, spice, smoke, umami agents. I used chartreuse-hued coal oil, mauve dashi, pink rose hips. Sometimes the SCOBY played a supporting role, sometimes as a focal point and ultimately as the narrator. With each experiment I asked: how can I create a dish that is playful and arouses all the senses?

seared duck heart, rhubarb, coal oil and kombucha mother

seared duck heart, rhubarb, coal oil and kombucha mother

I worked on many different applications of the mother. From dehydrating it to form a shell enclosing brined duck tongues, to dicing it to juxtapose with blanched squid. I also made a variety of kombuchas to generate different types of mothers: rhubarb, elderflower, black pepper, cucumber and even one with oysters. I mixed the acidic liquids into creams and made sorbets and granitas, continuing to explore the possibilities. Fluffy steamed buns soaked up pepper kombucha granita and cucumber kombucha sorbet as it melted into smoked mackerel and kombucha-infused cream. Each new interpretation yielded interesting results, but I struggled with the chewiness of the mother and keeping kombucha the star.

two trials of mother and squid with rhubarb kombucha and søl dashi

two trials of mother and squid with rhubarb kombucha and søl dashi

I made cucumber kombucha dumplings from blended cucumber, separating the juice from the pulp through a fine mesh sieve. With the cucumber pulp I added a splash of rhubarb kombucha. Using a very young kombucha mother, I cut 7cm circles to create dumpling wrappers. I plated the dish by creating a small lake of cucumber juice at the bottom of a wide ceramic bowl. The kombucha skin wrapped around cooled cucumber pulp was finished with toasted caraway seeds, a few drops of olive oil and sea salt.

cucumber 'dumplings' with kombucha mother, caraway, and olive oil

cucumber 'dumplings' with kombucha mother, caraway, and olive oil

Unlike other applications of the kombucha mother, the dumplings dish was on its way to success. The bite-sized dumplings and younger kombucha made it easier to chew through the mother. It provided a complementary balance between sweet and sour that paired nicely with the coolness of the cucumber. The toasted caraway seeds added a slight crunch and a hint of vegetal smoke. Unlike some of my other trials, this dish was well received. But I was also interested in the disgust factor and I wanted to push the relationship we have with food, sex and disgust through the use of the zoogleal mat.

Focusing on the mouthfeel of raw oysters, I made an oyster kombucha. When the mother was 5mm thick I cut a piece of the membrane into an oyster shape. I laid this new oyster in its shell and with a stroke of squid ink and a splash of dashi and suddenly the mother became the oyster.

the oyster mother 'oyster'

the oyster mother 'oyster'

There was a strange sensation when consumed. Slightly sour, salty and sweet the mother provided more chew than a real oyster and less burst of flavour, but still I found enjoyment in the gelatinous experience as it slid down my throat. Was this dish a novelty? Well-balanced? A success? That’s up to debate, but it provided me with a mind-manifesting object. Something happens in the brain and in the body when we try new things, as we build and dismantle preferences. Our likes and dislikes find companionship between past experiences and unknown futures. In the end, the kombucha mother may not become a popular menu item. As a food, it serves a different purpose.

Calibrating Flavour part 2: formulae for deliciousness

Added on by Kristen Rasmussen.

by Kristen Rasmussen

Enjoying food is similar to enjoying music—we have preferences from an early age, but by learning more about a longtime favorite or exploring a new genre, we can better understand and appreciate nuances and new styles. Cuisine is not one-note, but rather a combination of factors: the central baseline of chemicals that register taste, the chords and melodies determined by hundreds of aroma compounds, and the tangible percussion of texture and trigeminal effects, such as temperature and spice, all merge to create the songs of gastronomy. Like music, we all come to the table with culture and history that shape our experience and no one combination will work the same for every diner. Given this high potential for variation and the subjective nature of preference, how do we know what makes for a successful combination of ingredients? 

In a previous article, Calibrating Flavour Part I: measuring the senses in a fast-paced world, I discussed the some of the challenges of sensory analysis and described a few innovative sense-measuring tools that are less time-intensive than the ‘gold standard’ evaluation process. Yet although these tools provide a valid overview of certain measurable characteristics such as similarity between samples, they do not get at the (IMHO) most important attribute when examining food—deliciousness, or shall we say in sensory terms, ‘hedonic value’. The study we conducted using these tools to investigate various aromatic spice blends showed us how compounds identified through chemical analysis translate to perceived flavour, but that is only part of the story. To get the full picture, or hear the full song, we need to understand how those blends of chemical and physical attributes inform preference, from a variety of different viewpoints.

One theory for why a cook or chef might want to use a certain combination of ingredients is the concept of ‘food pairing’. Food pairing hypothesises that ingredients sharing more flavour compounds are better suited for each other than those that share fewer flavour compounds. An obvious example of this concept would be garlic and onions, whereas tomato and parmesan or shrimp and white wine are less obvious examples of the pairing hypothesis, yet still intuitive. Even more extreme are the white chocolate and caviar or dark chocolate and blue cheese pairings that were introduced to menus specifically because of this food pairing theory and the discovery that these food duos shared a high number of flavour compounds (an impressive total of 73 for dark chocolate and blue cheese). This theory is so prevalent that it is a registered trademark and there is even a website dedicated to helping chefs and bartenders understand and use it. 

Figure 1. Example of ingredients that share many and few compounds.

Figure 1. Example of ingredients that share many and few compounds.

Apricot galette contains butter, flour, sugar, and nuts, which share many compounds. (photo by the author)

Apricot galette contains butter, flour, sugar, and nuts, which share many compounds. (photo by the author)

Food pairing is such a popular concept because it is relatively easy to understand but, fortunately or not, we humans and our desires are a bit more complex than this hypothesis alone can explain. Furthermore, it is difficult to quantify something with such an artistic element as gastronomy using so simple a formula. For a more complex view of the issue, one can look to the flavour network illustrated by Yong-Yeol Ahn and colleagues (2011). In their research, these Harvard scientists evaluated the shared flavour compounds in ingredients from over 50,000 recipes. What they found seemed to confirm the pairing hypothesis —a lot of ingredients having a high number of shared flavour compounds are in the same recipes, but it held only for Western European and Northern American recipes. For recipes hailing from Southern Europe and East Asia, it was the opposite story—foods are more likely to be paired with other foods if they have fewer flavour compounds in common, giving birth to the idea of ‘antipairing’. 

Figures 2 and 3. Example of how ingredients in North American recipes tend to share many compounds, whereas ingredients in East Asian recipes tend to share few compounds.

Figures 2 and 3. Example of how ingredients in North American recipes tend to share many compounds, whereas ingredients in East Asian recipes tend to share few compounds.

They go on to point out that these trends diminish significantly when the most characteristic ingredients of each cuisine are taken out of the equation. For example, when milk, wheat, and eggs are removed from North American recipes the resulting combinations demonstrate the food pairing hypothesis less robustly, and the same is true for anti-pairing of ginger, pork, and onion in East Asian recipes. At first glance, this observation supports the ‘flavour principle’, or the concept that the difference between traditional cuisines can be reduced a few ingredients (Rozin, 1973). However, if an observation is only true under the condition that the key ingredients in a recipe are removed, is it really worth noting, or is the recipe transformed beyond recognition and the observation rendered rather unuseful? I would also argue that the flavour principle itself is misguided because not only can a cuisine not be reduced to a set of ingredients, but a cuisine, its dishes, their variations, and an eater’s interaction with them, cannot be reduced to a set of factors—there is so much more at play. Consider the difference between consuming a meal in haste with a phone or computer nearby, and eating that same meal around a table in the company of others. Our daily companions and our broader culture not only determine what is considered acceptable as food, but also what is considered acceptable as the food environment—communal dining, conversation or no, sitting on chairs or on the floor or reclining, eating with cutlery or hands, take-out, and all manner of distractions. 

The rosemary is an example of using the anti-pairing concept in a recipe where most other ingredients contain many shared compounds. (photo by the author)

The rosemary is an example of using the anti-pairing concept in a recipe where most other ingredients contain many shared compounds. (photo by the author)

The food environment is just one factor beyond ingredient combinations that can not be ignored when exploring cuisine. Further important factors are, for example, culture, history, and relationship to innovation. By labeling certain cuisines with a formula for deliciousness—food pairing for Western Europe and North America and food anti-pairing for Southern Europe and East Asia—we are making assumptions that there is a correct way to create food in a given region. These assumptions make us more likely to disregard the diner’s background and context, and forget that norms and standards are constantly reorganising. Just like jazz, during its emergence, was (and in many cases continues to be) a musical revelation, recipes, menus, and new food genres do the same for the gastronomic world. These new ideas aren’t always good ones, and they often take some time to be iterated, refined, and accepted, but I believe it’s important to always keep trying rather than assume that the story is set in stone. 

Parmesan cheese, olive oil, and zucchini share few if any compounds—but the combination sure works for me.

Parmesan cheese, olive oil, and zucchini share few if any compounds—but the combination sure works for me.

Another idea illustrated in the Ahn article on flavour networks is that all foods have a ‘fitness value’, which is determined by a combination of factors such as nutritional value, availability, antimicrobial properties, flavour, etc. In theory, foods are used because of their fitness value, which makes sense when you think about acidic ingredients like lemon or vinegar, that have a tartness to balance other flavours and create an inhospitable environment for “bad” bacteria. However, the elements of sensory and aesthetic preference  that should be included as part of a food’s “fitness” are, as we have seen, difficult to quantify and evaluate. There are objective food fitness factors that make up part of the story, but there are also subjective factors without which the story makes no sense.

Determining the formula, or musical arrangement, for deliciousness is no easy task—probably because there is no one such arrangement in the first place. Foods do have certain measurable characteristics, but we also all taste food with a personal perspective—which is exactly what makes gastronomy fascinating for both the cook and the eater. Research investigating connections between flavour compounds and preference, such as those mentioned above, are vital to better understanding cuisine, but it is imperative to remember all the other factors that contribute to our eating experience, and, I would say, to never stop listening to new gastronomic music. 


Ahn, et al. Flavour network and the principles of food pairing. Scientific Reports 1, Article number: 196 (2011).

Rozin, E. The flavor-principle cookbook. Hawthorn Books, Book Club Ed: 1973.

Artist-in-residence: Nukazuke pathways

Added on by Rosemary Liss.

by Rosemary Liss.
Check out Rosemary's first post, a slideshow of images from her summer as our artist-in-residence,

as well as our first short post on nuka from a few years back.

My interest in nukazuke stems from my more general interest in the physical relationships between bodies and food as a life-sustaining force. I was introduced to the nuka duko (or nuka pot) on my very first day working at Hex Ferments, a company that creates kombucha, kimchis and kraut in Baltimore, Maryland. This magical process inspired later artistic projects both visual and comestible.

The nuka is a perfect example of a process that was born from utilising waste. Its origin finds roots in the Edo period of Japan when the milling of rice rose in popularity. The by-product of polishing rice is the rich outer membrane also known as bran. By adding a salt brine and other inoculants from seaweed to sake, a nutrient-dense pickling bed is cultivated that, if well-tended, can pickle raw vegetables from morning to evening. This process, born from preservation and waste reduction, transmutes raw materials into a microbial-rich habitat.

I was initially drawn to the daily ritual of tending the nuka because it goes beyond food preparation and become a metaphor of life cycles. The bed is a living organism, a community of bacteria and yeast, feeding, digesting and expelling. Interpreting the nuka in one’s own environment cultivates not only a somewhat new kind of pickling machine, but also opens up new forms of living (for microbes and for humans) layered between the global and local aspects of one’s own foodshed. As I tended to our Baltimore pot—aerating the paste, removing the pickled vegetables, adding fresh ones—I began to see its possibilities for my own research and exploration. And I saw how different raw materials from Denmark might respond very differently from those found in Japan.

I found a deep connection to this daily process. When I stirred the pot my mind would slip into quiet and a sense of calm materialised; my body moved automatically with the soft sand-like paste and we become one. This past January I was a resident artist at the Vermont Studio Center. I spent a portion of the program exploring this certain intimacy. Removing the comestible component of this process by replacing the vegetables with wood and ceramic objects I created a performance piece to showcase the nuka’s meditative qualities.

While in Vermont I applied to be an intern at Nordic Food Lab. I proposed doing more research on the Nuka, but in context with the Nordic landscape. In my proposal I stated:

“Like many ferments, the Nuka is influenced by its environment, and a pot cultivated in Baltimore would produce a uniquely different mouthfeel from one in Copenhagen. My project would focus on producing a Nuka Pot connected to Denmark’s terroir as a way to study its microbial influence.“

When I came to the Lab, I wanted to continue to expand on my relationship with Nuka, but in a new environment. I saw this process as a lens to study the Nordic terrain—I would recontextualise the process within the structure of my available materials. It was a starting point to begin to understand the importance of using what a particular ecosystem provides. In my notes I wrote:

“I will begin my research studying the ability of a variety of traditional Nordic grains to find a good alternative to rice bran. I will create multiple nuka pots in 5 L containers with the controls being set for the same amount of bran and salt in each pot and only carrots as the pickling object. Once I have found the ideal bran, I will broaden my research to explore a variety of inoculates including: seaweed, beer, and miso. I will explore whether these ingredients are necessary to help the nuka ‘bed’ ferment and protect from spoilage. When I have found the most ideal flavor profile and combination of ingredients I would like to play with burying various vegetables, fruits and proteins and see which ingredients produce the best nuka pickles.”

Specific requirements for the nuka:
1. The pickled vegetables have a complex flavour, tangy and aromatic from the pickling medium, with a crisp yet yielding texture;
2. The pickling bed has good consistency: not too moist nor too dry (ideally the texture of wet sand);
3. The pickling bed can make good pickles in 6-12 hours.

I did research on four different heritage grains. My colleague Jonas, our team sourdough baker, introduced me to grains I had never heard of, like Øland and Dacke wheats. He taught me how to mill my own flour, removing the hull or husk of the grain. I loved using the small stone grinder to turn whole kernels into flour. This process was beneficial both to Jonas and to me. As the wheat was milled and sifted, he was left with fresh flour for baking, and I was left with its by-product, the bran, for my nuka pots. It was a perfect relationship, especially in a space that focuses on finding latent potential in all kinds of raw materials and utilising what might otherwise be seen as waste.

Nordic Food Lab is a hive of interdisciplinary learning, but it is still a laboratory. And when you do research-based projects to try to generate knowledge it is vital to set up controlled experiments. Below are my notes from my first experiment.

It took a while for the beds to ferment and the salt content remained high. Every day I would aerate the nuka bins and remove the pickled carrots. I tested the “soils'” pH content and added fresh veggies. The nuka ranged from dry to sticky and the four types of bran had a fluffier consistency than the rice bran I was used to.

Different nuka inoculants

Different nuka inoculants

Obtaining organic, local carrots was not as easy as I had hoped, so I switched my control substrate to asparagus, which is bountiful in the summer months. When pickled, the tough skin would soften and become prune-like as the membrane began to break down. The asparagus kept a nice crunch with a burst of briny juice ranging from sour to sweet. There were slight variations in flavour and texture depending on the bran, but it did not obtain the complexity of flavour I was used to with a traditional rice bran nuka.

Process and tasting notes from the nuka trials.

Yet still from these trials I had discovered that the Øland was the most suitable bran. Focusing on one pot for my second experiment, I got a much larger batch of pre-milled Øland. For this round I inoculated the batch with pieces of sourdough baked in the lab, sugar kelp, eggshells, and roasted koji miso. The bran fermented more quickly and the pH began to drop. Immediately the flavours were more intense and a complex umami taste developed. The bed, however, remained fluffier than my first trial batch of Øland bran and began to smell of ethanol. For my first batch, I milled the Øland wheat myself; for the second batch, I used bran from wheat that had been milled at the farm. The second batch was fluffier and did not stick together well, which I believe might have come from the two brans having different final compositions—the second batch bran had more efficiently removed the husk resulting in its particular certain texture, while my own bran seemed to have a higher concentration of flour remaining, which provided more texture to the paste and probably was also facilitating the growth of metabolising yeast and LAB.

By the beginning of July I had eaten so many pieces of asparagus that they began to blend together and my tongue had difficulty discerning between the nuances in nuka pots and fermentation times. The pH did continue to go down, but so did my energy level. I felt uninspired and the act of churning the pot everyday became a chore. I started to get jealous of colleagues who were experimenting with a variety of dishes and the excitement that followed each success and failure.

I continued to aerate, remove and replace vegetables in the new nuka for another week. The pH went down slightly, but the nuka bed did not yield tasty results and the bran remained fluffy, lacking the pasty, sandy consistency of the rice bran. After some deliberation, I put the project to bed and composted the nuka.

I did find that Øland wheat was a suitable alternative, but suitable doesn’t necessarily mean exciting or delicious. Ultimately, none of the grains I tried really compared to the flavour and texture of rice bran. I also began to understand that the purpose of the lab isn’t to take a traditional process and make it Nordic, but to find something in one’s environment and cultivate it through experimentation until you create something that is delicious unto itself. It was about exploration and playfulness, feeling alive and coming into that space everyday to share with my colleagues interesting tastes and new combinations of ingredients and dishes. I found the routine and body connection in other ways. Feeding sourdough and making rye bread, gutting fish, and processing bee larvae. No longer was I second guessing my role and I began to play. 

While my nuka was a failure, it was also a gift. I had to struggle through it to find meaning and context for other projects. I would hurry though my own research so I could have more time talking tempe with Bernat or learn how to make the perfect tortilla with Santiago. Meanwhile a kombucha SCOBY I had brought all the way across the Atlantic had settled nicely into its new environment and multiplied.

At that time I was thinking about the intersection between eating and disgust. Bernat had just presented some trials from his tempe project at a conference put on by the Asian Dynamics Initiative at the University of Copenhagen, entitled ‘Food, Feeding, and Eating in and out of Asia’. The team was surprised to discover the intensity of the audience’s reactions. Those that had grown up eating traditional tempe found this new softer, chewier and mildly acidic cousin revolting (more info in part 2 of Bernat's tempe research results). It brought up many questions about how cultural perception creates a framework for taste. With these discussions in mind I started to experiment with the SCOBY itself as an edible substrate, playing with similar themes. My adventures cooking with kombucha began and my nuka experiments came to an end.

But really it's not the end. The work becomes part of a greater rhizome of material generated by the lab; these small failures are part of a larger experience. We are not specialists, were are enthusiasts. Most of us don’t come from long generations of singular producers or craftspeople. We are looking around at the world with open minds and excited hearts and we are making a big mess and out of this mess we find new and experimental ways to think about what growing, preparing and consuming food means to us.