There will be slime

Added on by Edith Salminen.

by Edith Salminen


Nordic people love fermented milks, with an average intake per person of 100g a day. We have in the Nordic region a distinctive subfamily of fermented milk and cream products sometimes referred to in English as the “ropy milks of Scandinavia”. These ropy milks are rather similar in flavour and acidity, but differ in consistency and mouthfeel. The Finnish one is called viili and it is a traditional fermented milk product involving lactic acid bacteria (LAB) that enjoy ambient temperatures between 17 and 22 °c, as well as a surface mould which makes the product unique in taste, aroma and appearance compared to all other Nordic fermented milks. The mould growing on the surface is Geotrichum candidum (the same mould which plays a crucial role in the development of certain cheeses). It feeds on the cream and forms a tasty, slightly fuzzy upper layer.

The slimy ropiness of viili is created by a specific strain of LAB called Lactococcus lactis subsp. cremoris. Other LAB strains used in industrially produced viili are Lactococcus lactis subsp. lactis biovar diacetylactis (contributes to flavour) and Leuconostoc mesenteroides subsp. cremoris. These LAB strains produce long chains of exopolysaccharides. Exopolysaccharides are long chains of many (‘poly’) sugars (‘saccharides’) that are excreted from the cell (‘exo’) as part of its metabolism. Other, more known exopolysaccharides commonly used in the food industry are Xantan and Gellan gum.

Viili was traditionally made in wooden barrels, often made of alder wood. Nowadays, one doesn’t need to carve a barrel of alder: making viili is a no-brainer. If you have full fat, good quality, unhomogenized cow’s milk, a 200ml plastic or glass jar and a viili seed you’re good to go. Go ahead and try it for yourself. Let there be slime!

Our viili gets its own fridge drawer.

Our viili gets its own fridge drawer.

Nordic people love their fermented milks, with an average intake per person of 100g a day. Finns and Danes rank highest in the bunch with a ravishing 41 kg per person per year (Fondén & et al. in Tamine 2007)! Yet what is perhaps less known is many people’s proclivity for a bit of slime in their fermented milk.

We have in the Nordic region a distinctive subfamily of fermented milk and cream products that Harold McGee refers to as the "ropy milks of Scandinavia" (McGee 2004, 50). These yoghurt-like substances are known under different names depending on their geographical origins: långfil in Sweden, tettemelk in Norway and viili in Finland. These ropy milks are rather similar in flavour and acidity, but differences in consistency and mouthfeel are noticeable even to a non-Nordic palate.

I am Finnish so viili is my bread and butter. Let me tell you a story of viili.



Viili is a traditional Finnish fermented milk product involving mesophilic bacteria[1]. In some scientific papers it has also been classified as a “mould-lactic fermentation product” (Tamine & Marshall in Law 1997). Viili is the modern version of old-school filbunke traditionally produced in Sweden, from where it made its way to Finland when the two countries were one roughly from the 12th century up to the year 1809 (Fondén & et al. in Tamine 2007). It is hard to say how long viili has existed, but there are records of it being produced and consumed in Finland since the 19th century. Somewhere along the way, distinct from its Swedish ancestor, viili gained a mould growth on the surface, which makes it unique in taste, aroma and appearance compared to all other Nordic fermented milks (Law 1997). Beautiful, delicious surface mould.



Today, viili is mostly considered as breakfast or a snack, whereas back in the days it was regarded as a full meal, especially in summertime (Linquist 2009, 79). Nowadays viili is most often consumed topped with sugar and cinnamon, or served with fruit. To give viili a modernising face-lift, fruit-flavoured and -coloured industrial viili called Viilis was introduced to the market in the 1980s and continues to be popular among children (Tamine & Robinson 1988).

The reason why I decided to get to know my beloved slimy friend more deeply is because I have been taking it for granted all these years. Available in any little kiosk or food store in Finland, viili is no longer an artisan product as it used to, the viili seed passing from mother to daughter. I want to change that.


Once upon a time…

The first commercially sold viili was produced in a sauna hut by a riverbank close to the town of Sipoo in South-eastern Finland in 1929 (Ingman 2013; Wallén 2003). A young man called Hjalmar Ingman made his first trip to Helsinki to sell his viili – thirty 1-liter wooden jars of it to be exact – on June 23rd of that year. Safe to say his efforts paid off. Ingman’s viili was a succulent success. Except for a brief halt in business from spring to October 1941 due to WWII, Ingman’s viili business kept growing. In 1960, he founded Hj. Ingman Ky, a public organization owned by a group of municipalities. That is also when his viili would become available in the first milk shops such as Wickström, HOK and other Finnish supermarkets (Wallén 2003, 220).

Determined and young Mr. Ingman (Wallén 2004).

Determined and young Mr. Ingman (Wallén 2004).

As mentioned above, viili was traditionally made in wooden barrels. According to old sources, the best wood to use was alder wood. Whether the wood added some important aromas or flavour to the final product or had some other particular function is uncertain, but one could guess it did. When time to eat, the viili barrels (hence the Swedish name filbunke, or 'viili bowl/barrel') were placed in the middle of the table for shared consumption. The unwritten eating rules were common knowledge: one should always keep to one's own corner of the barrel and one was never to only skim the creamy surface that for many was the most delicious part. From the 1920s onward the wooden barrels were gradually replaced by single serving glass jars (Lindquist 2009, 78). Nowadays, viili is sold in plastic single-portion-sized (250g) containers sealed with an aluminium foil cap.


It’s all in the slime

What is so precious and exciting about viili is its distinctive ropy and gelatinous consistency, which gives it its characteristic mouthfeel. Other Nordic fermented milk products with mesophilic bacteria have this to some degree, but viili is downright the slimiest I’ve encountered. Slurp a spoonful of viili and you can feel how it holds together firmly but softly. In fact, viili is so cohesive that if some of the viili spills out from its container the rest of it will most probably be dragged out of the container too. It’s like a dairy slinky. As a kid I remember thoroughly enjoying and playing with this feature.

Ropy viili.

Ropy viili.

The slimy ropiness is created by a specific strain of lactic acid bacteria (LAB) called Lactococcus lactis subsp. cremoris. Other LAB strains used in industrially-produced viili are Lactococcus lactis subsp. lactis biovar diacetylactis (contributes to flavour) and Leuconostoc mesenteroides subsp. cremoris (Meriläinen 1984). These LAB strains produce long chains of exopolysaccharides at the correct fermentation temperature to create the characteristic consistency and also contribute to the aroma and flavor profile of viili (Kahala & Joutsjoki 2012, 177).

Exopolysaccharides are long chains of many (‘poly’) sugars (‘saccharides’) that are excreted from the cell (‘exo’) as part of its metabolism. They have multiple applications in various food industries, as their properties are almost identical to different plant and algal gums currently in use (e.g. xantan gum, gellan etc.). In general, the various exopolysaccharides are increasingly used to attain certain wanted textures and consistency as well as to improve physical stability in food items (Giavasis & Bilideris 2007). To give you a concrete and more familiar example, Gellan gum (E number E418) forms soft, elastic, transparent and flexible gels, but forms hard, non-elastic brittle gels once de-acylated. Xanthan gum (E number E415), another common exopolysaccharide and often used in gluten-free baked goods, hydrates rapidly in cold water without lumping to give a reliable viscosity, encouraging its use as thickener, stabilizer, emulsifier and foaming agent.

[1] Gellan gum molecule. Source: Water Structure and Science, Martin Chaplin, 2012.

[1] Gellan gum molecule. Source: Water Structure and Science, Martin Chaplin, 2012.

[2] Xantan gum molecule. Source: Water Structure and Science, Martin Chaplin, 2012.

[2] Xantan gum molecule. Source: Water Structure and Science, Martin Chaplin, 2012.

Moreover, the naturally-occurring exopolysaccharides that give rise to sliminess also prevent syneresis (the expulsion of water from a gel) and graininess, resulting in a pleasant natural thickness in the product (Macura & Townsley 1983). According to Sundman, It is thanks to these exopolysaccharides that the Nordic ropy fermented milks, and viili in particular, keep longer than many other fermented milk products under the same conditions (Sundman 1953). 

[3] Lactococcus lactis subsp. cremoris, bar: 1 µm. Photo by Bart Weimer, Utah State University.

Certain LAB strains, but also yeast and fungi, excrete exopolysaccharides as part of their metabolism. Research shows that these molecules have beneficial effects to human health, being antitumorous, immunostimulatory, hypocholesterolic and hypoglycemic (Giavasis & Bilideris 2007.) The exopolysaccharides do not interact directly with the pathogenic agent, but they do stimulate the immune system to respond and are therefore referred to as “biological response modifiers” (Giavasis & Bilideris 2007).

(For more on lactic acid fermentation, read this article on the blog and listen to this podcast of one of our talks for noma stagiaires and staff.)


Delicious mould

Often, moulds and fungi tend to not tolerate lactic acid bacteria very well, that is why you rarely find, for example, green mould on your yoghurt (unless its very old) (Frisvad 2014, personal communication). But what distinguishes viili from its other Nordic counterparts is in fact its delicate mouldy surface. When making viili, the milk cream rises to the surface (a normal occurrence when unhomogenized milk is left to stand). Many Finns consider this upper layer the most delicious part of viili, as do many of us at the lab. This deliciousness is not only because it is composed of cream (duh) – the mould Geotrichum candidum (which plays a crucial role in the development of certain cheeses, particularly small-format goat’s cheeses from the Loire Valley) feeds on the cream and forms a tasty, slightly fuzzy upper layer (Kurmann et al. 1992). 

[4] Geotrichtum candidum x1000 LPCB stain. Photo by George Barron 2013. 

[4] Geotrichtum candidum x1000 LPCB stain. Photo by George Barron 2013. 

The G. candidum also contributes to viili’s overall flavour formation giving it some fruity and mushroomy notes. Like most other moulds, G. candidum is aerobic and therefore only develops on the surface of the viili (Frisvad 2014 personal communication). This mould also consumes lactate (any salt or ester of lactic acid). This process lowers the acidity in viili resulting in a mild and delicate, slightly acidified milk flavour – less acidic than the similar Swedish långfil, for example. As moulds consume oxygen and produce carbon dioxide, an airtight viili jar bought from the store can be slightly carbonated when opened – totally fine, and totally tasty (Kahala et al. 2008,105). Some of this carbonation could also be due to heterofermentative LAB. In addition to G. candidum, traditional viili also contains the yeast strains Kluyveromyces marxianus[2] and Pichia fermentans. In industrially-produced viili, however, these two yeast strains are considered contaminants.


All for slime and slime for all

Making viili is a no-brainer. If you have full fat, good quality, unhomogenized cow’s milk, a 200ml plastic or glass jar and a viili seed you’re good to go (unless you happen to be located in a very warm climate). When in Finland, one can walk into practically any little food store or kiosk and find viili next to milk, butter and yoghurt. In Denmark on the other hand, viili is nowhere to be found, but that’s what kind mothers are for. A quick call to Finland and I had both a viili seed and my mother in Copenhagen a week later. That’s what I call a special delivery.

But do not worry, fellow viili-lover – there is another way to get your viili going if you don’t happen to have a mother in Finland. To my delightful surprise while reading Sandor Katz, I discovered that a viili seed, a real traditional one, was transported dried in a piece of cloth to the United States over a 100 years ago. The family with Finnish origins, now American, run a webstore called GEM Cultures selling various microbial cultures that have been in their family for ages, and among them a viili culture. Similar online stores selling viili seeds are Happy Herbalist, Cultures for Health, and Yemoos Nourishing Cultures. I tried the latter, just out of curiosity and because they send you the seed dried. I also discovered a woman from Norway named Eva Bakkeslett, an artist and cultivator who as a part of her artistic work uncovers forgotten or rejected practices, concepts and cultures which she then cultivates and shares with others. Eva has made a whole anthropological art project on my beloved slimy milk! Check out her work here.

It never ceases to amaze me when, concentrating on one single esoteric subject, one finds leads and connections all over the world. We often become so used to our distinctive cultural food items that we forget their peculiarity and their beauty. Stumbling upon these viili lovers all the way in the United States really made me appreciate this odd Finnish dairy product even more.

This is not a drill.

This is not a drill.

As we speak, there are containers of different sizes all over the lab breeding slimy deliciousness. Though I have to admit that stepping outside of my culturally constructed box when it comes to viili has been challenging. What to do and what to create with something that is already so good and special as it is? How to give a new angle to it without losing its essential character? Luckily this is what we do here at the lab and I’ve got a great team pushing me to rethink viili and all its potential. The full results of my viili experiments remain to be seen, but what I know without a doubt is that I have an important mission to spread the seed. Getting the sporadic visitors and curious passers-by to take home a few tablespoons of viili is my immediate aim. So far viili seeds have travelled to Norway, Austria, Greece and back home to Finland. Slowly but surely, my humble Finnish ropy milk will take the world over. There will be slime –

to be continued...



[1] Mesophilic bacteria are medium temperature bacteria, a group that grow and thrive in a moderate temperature range between 20°C and 45°C. The optimum temperature range for these bacteria in anaerobic digestion is 30°C to 38°C.

[2] This yeast is also produced commercially as a nutritional and bonding agent for fodder and pet food, and as a source of ribonucleic acid in pharmaceuticals.



[1] (Accessed March 24th 2014).

[2] (Accessed March 24th 2014).

[3] (Accessed March 18th 2014).

[4] (Accessed march 18th 2014).



Fondén R. et al. “Nordic/Scandinavian Fermented Milk Products” in Fermented Milk, Wiley-Blackwell, 2006.

Frisvad, Jens Christian, personal communication at the Lab on March 12th 2014.

Fuquay et al. Encyclopedia of Dairy Sciences 2nd Edition Second Edition, Academic Press, 2011.

Giavasis I. & C. G. Biliaderis “Microbial Polysaccharides” in Functional Food Carbohydrates, Eds. Biliaderis & Izydorczyk, 2007.

Kalaha et al. “Characterization of starter lactic acid bacteria from Finnish fermented milk product viili”, Journal of Applied Microbiology, vol 15, 2008: 1929-1938.

Kahala M. & V. Joutsjoki “Traditional Finnish Fermented Milk “Viili”, Handbook of Animal-Based Fermented Food and Beverage Technology, Second Edition, Eds. Y . H . Hui, E . Özgül Evranuz,  CRC Press, Taylor & Francis Group, 2012.

Kurmann, J. et al. Encyclopedia of Fermented Fresh Milk Products: An International Inventory of Fermented Milk, Cream, Buttermilk, Whey, and Related Products, Springer, 1992.

Linquist, Yrsa Mat, måltid, minne – Hundra år av finlandssvensk matkultur, Svenska litteratursällskapet, Helsinki, 2009. 

Law, B.A Microbiology and Biochemistry of Cheese and Fermented Milk Second Edition, Chapman & Hall, London, 1997.

Macura D. & Townsley P. M. “Scandinavian Ropy Milk – Identification and characterization of endogenous ropy lactic streptococci and their extracellular excretion”, Journal of Dairy Science, vol. 67, 1984: 735-744.

McGee, H On Food and Cooking: An Encyclopedia of Kitchen Science, History and Culture, Hodder & Stoughton, London, 2004.

Meriläinen V. T “Microorganisms in fermented milks: Other Microorganisms”, Bull. of Int. Dairy. Fed., vol 179, 1984: 89-93.

Sundman V. “On the protein character of a slime produced by Streptococcus cremoris in Finnish ropy sour milk”, Acta Chem. Scand., vol 7, 1953: 558-560.

Tamine A. Y. Fermented Milks, Wiley-Blackwell, 2006.

Tamine A.Y. & Robinson R.K. “Microbiology of yoghurt and related starter cultures”, Yoghurt: Science and Technology. Eds. Tamine A.Y., Robinson R.K. Cambridge, Woodhead Publishing Ltd. 2007, 468-534.

Wallén, B  Juusto-Uusimaa: Itä-Uudenmaan kadonnut juustonvalmistusperinne/Ostnyland : Den försvunna osttillverkartraditionen i Östra Nyland, ETC-consulting, Finland, 2004.





Vinegar Science pt. 5: Recipes

Added on by Arielle Johnson.

by Arielle Johnson


What follows in our last post in this 5-part miniseries on the hows and whys of vinegar making are some of the recipes we developed using the previously discussed techniques and methods. There are three recipes: one for celery vinegar using the ethanol addition method and single (acetic) fermentation; one for strawberry vinegar using a double (alcoholic and acetic) fermentation and aquarium bubbler; and one for roasted koji ale vinegar, using a triple fermentation (fungal saccharification, alcoholic, and acetic), and passive aeration.

Young Celery Vinegar:

1. Juice celery in a juicer – you should get a yield in juice of approximately 50% of the initial weight.

2. Add high-proof alcohol to the celery juice until the mixture has an ethanol concentration of 6-8%. If you're using 80 proof liquor to do this, only 40% of what you're adding is ethyl alcohol so plan accordingly.

3. Add 20% of a raw, unpasteurized vinegar you like the flavour of – either a previous batch of homemade vinegar, a commercial vinegar, or vinegar mother.

4. Submerge an aquarium air pump and airstone in the vinegar, cover the container with something air-permeable, like cheesecloth with a fine weave or a side towel ­(you'll want to keep fruit flies out but let the air you're pumping in escape) and aerate the mixture until it tastes strongly of vinegar, approximately 3-8 days.

Alas, a Dane wrote the names, in whose language celery has two 'l's (bladselleri)

Alas, a Dane wrote the names, in whose language celery has two 'l's (bladselleri)

Strawberry Vinegar:

1. Juice strawberries.

2. You want juice with 12.5-15% sugar to reach 6-8% alcohol post-fermentation. Your juice alone will probably not have this much sugar. Split the juice into two even volumes, reduce one on the stove by about 3/4, then combine them to attain this range. This method assumes you have about 8% sugar in your strawberry juice to begin with. If you have a refractometer, take measurements and calculate; or, cowboy it by taste and let us know how it turns out, we're curious.

4. Add champagne or white wine yeast to your strawberry juice, seal it with an airlock, and let it ferment until it stops bubbling (it should taste dry and alcoholic), somewhere around 7-14 days.

5. Rack the strawberry wine off the yeast lees, add raw unpasteurized vinegar at 20%, and either aerate or let stand for 2-4 months.

Roasted Koji Ale Vinegar (with botanicals)

(Makes 25 L of beer, 30 L of vinegar)

1. Make Koji: Soak 1.5 kg of pearled barley overnight, steam it for 1.5 hours, cool to 35˚, inoculate with 1.5 g koji spores (1g/kg dry grain if using pure spores; 20g/kg if using koji-kin), spread into a 2cm layer, cover with a damp towel, and incubate in a humid room at 30˚. Stir and turn after 6, 12, and 18 hours. The koji is ready when a fuzzy white mycelium binds the grains together; if it has started turning green, use these parts for spores but don't cook with them. Roast the koji at 175°, mixing frequently, until it is dark golden brown.

2. For easier fermentation and improved beer flavour, make a yeast starter. Make 2L of wort the day before brewing by diluting malt extract or dried malt in boiling water to about 12-13% sugar, let cool, and add a packet of dried yeast or, better, a tube of yeast culture like White Labs California V Ale Yeast, and let it grow for 24 hours before you brew. Adding this larger amount of yeast to the 25 L of wort stresses the yeast less.

3. Grind 4500 g of Maris Otter Pale Malt or another similar malt, and 1900 g of roasted barley koji.

4. Pre-heat a large insulated container such as a large thermal drink dispenser or cooler by pouring boiling water into it. This container is your ‘Mash Tun’. It will make your life much easier if it has a tap at the bottom out of which you can drain liquid, and even more so if you attach a piece or a cylinder of wire mesh to the opening as a filter)

5. Heat 15 L of filtered water to 72°C. This is your ‘strike water’, and you want it at a temperature so that when you mix it with your grain, they will be at 65°C. Use this calculator for a more precise estimate.

6. Combine the grain and the heated water in the pre-heated insulated container, make sure the temperature of the mixture is about 65°C, stir it, put a lid on it, and let it sit for an hour. Right now you've activated amylolytic enzymes in the malt which are converting starches into sugars, and these sugars as well as other flavour compounds are being extracted into the water. The extracted grain is your wort.

7. Heat another 15 L of water to at least 72°C; it can be boiling.

8. After an hour, slowly drain the wort off the grain with the tap on your mash tun. This is called lautering. Minimizing exposure to air, for example by covering the spout with tubing, will prevent oxidative flavors. Your wort will probably be fairly cloudy. If the mash tun has no tap, you can pour all of it through a strainer to separate the spent grain from the wort.

9. To filter the wort further and extract more sugar, slowly pour the drained wort over the grain bed again one or two times, preferably through some kind of perforated plastic so the wort trickles over the whole surface and contacts all the grain.

10. Pour the second batch of 15 L of water slowly over the mashed grain and collect it. Mix the original wort with this second batch of wort. [i]

11. Let the wort cool and take a sample to measure its sugar content by specific gravity. This is done with a hydrometer, which floats in the wort and measures its density by how high or low it floats. Assuming you'll have a small amount of sugar and other dissolved solids left when the yeast have finished their fermentation, you want an original gravity of about 1055-1060, which means that the wort has a density that is 1.055-1.06 times that of water. A higher gravity means higher sugar, and either a sweeter or higher-alcohol beer. You can add water or boil down to adjust the gravity. You can also check the sugar content with a refractometer, which measures degrees brix, or percentage of dissolved solids calibrated to sucrose.

12. When the wort is at about room temperature, add yeast. We recommend White Labs Burton Ale Yeast, WLP023, as a starting point.  Put the yeasted wort in a sealed container with an airlock and let it ferment until you like the sweetness-alcohol balance; for vinegar you may want to stop it before it gets completely dry. This will take about 1-2 weeks. Either at this point or at the next step when you add vinegar starter, add 0.5-5% by weight of botanicals, depending on intensity and desired aromatic balance. We have used juniper berries, juniper wood, pine needles, liquorice root, and kelp.

13. Add 20% of the volume of beer of unpasteurized raw vinegar to the beer. Cover the container with an air-permeable cover, like a clean kitchen towel or muslin, and let it sit in a relatively warm place for 2-4 months, tasting every 2-4 weeks, until it reaches an acidity level that you like.


[i]            At this point, if you want to turn it into beer, you'd take hops, and boil some of them in the wort for an hour and then add the rest to boil for a short amount of time- the long boil transforms some of the hop compounds into bitter-tasting isomers, and the short boil will provide more hop aroma. Hopped beer can be made into vinegar, too.


Cricket Broth

Added on by Nurdin Topham.

Recipe development for our Pestival menu, by Nurdin Topham


As part of our own learning process we tried making some simple stocks to taste the inherent flavour of these different creatures, and to determine which was the optimal proportion of insect to use to impart the flavour.

After trying 10%, 20%, 30%, 40% we found that 20% was sufficient.

Once determining our basic ratio, we began adding a few more variables with the following recipes cooked sous vide at 85˚C for 1 hour.


White stocks

1. Cricket
60g     20%    Crickets
0.5g    0.1%     Sea salt
300g   100%   H20

2. Cricket & Kombu
60g     20%    Crickets
0.5g    0.1%     Sea Salt
2g       0.6%    Kombu
300g   100%   H20

3. Meal worm
60g     20%    Meal worms
0.5g    0.1%    Sea Salt
300g   100%   H20

4. Meal worm & Kombu
60g     20%    Meal worms
0.5g    0.1%    Sea Salt
2g       0.6%   Kombu
300g  100%    H20

Brown stocks

5. Cricket
60g     20%    Crickets, roasted 12 minutes @ 160˚C w/ 5g rapeseed oil
0.5g    0.1%     Sea Salt
300g   100%   H20

6. Cricket & Kombu
60g     20%    Crickets, roasted 12 minutes @ 160˚C w/ 5g rapeseed oil
0.5g    0.1%     Sea Salt
2g       0.6%    Kombu
300g   100%   H20

7. Meal worm
60g     20%    Meal worms
0.5g    0.1%    Sea Salt
300g   100%   H20

8. Meal worm & Kombu
60g     20%    Meal worms
0.5g    0.1%    Sea Salt
2g       0.6%   Kombu
300g   100%   H20


Tasting notes:

Screen Shot 2014-02-20 at 1.09.17 PM.png


The brown stocks were on the whole better than the white. With the browning masking some of the ‘unpleasant insect’ flavours. Cricket stocks were the more pleasant, naturally sweet and reminiscent of a prawn with a rounded biscuity savoury flavour. The Meal worm flavour was distinctively unpleasant – the aroma and flavour was hidden and improved with roasting which gave rise to chicken skin flavours and a crispy texture.

During a research visit to the Copenhagen zoo we learnt that often crickets’ diet is based on 1/2 cereals and 1/2 fish feed. We wondered to what extent the fish feed influenced the flavour of the crickets – more work could explore the effects of different feeding regimes on flavour. After speaking to different suppliers, we found crickets fed on grasses, not on fish food, and this improved the flavor dramatically.


Cricket Broth

After these initial trials we decided to pursue a broth as a concept to present the pure taste of insect. So we continued to investigate how to best obtain this purity of flavour. 

Our first task was to try testers of different stock cooking methods – in a pan, sous vide, and in the pressure cooker. We found sous vide to provide the cleanest flavour. 

Some notebook diagram notes:

fig 1: cricket broth trials

fig 1: cricket broth trials

fig 2: broth 2 - production batch

fig 2: broth 2 - production batch

Final broth recipe

Base brown cricket stock
1000g            100%             Water
200g             20%               Crickets roasted, preheated Rational 160˚C for 18 minutes
4g                  0.4%              Sea salt        

Combine in sous vide bag and cook @ 85˚C for 1 hour, then chill.

For the clarification & final broth

500g             100%             Brown cricket stock, reduced by half, cold
165g              33%               Crickets roasted in a preheated oven at 160˚C for 18 minutes
50g               10%                Carrot, finely sliced 2mm 
50g               10%                Shallot, finely sliced 2mm            
50g               10%                Leek, finely sliced 2mm                          
80g               16%                Chicken breast
50g               10%                Egg white
10g                 2%                Grasshopper garum


Puree chicken breast and egg white together at full power for 20 seconds. Mix ingredients together in a vacuum bag and seal under full vacuum. Cook at 85˚C for 1 hour, pass through a fine super bag, taste and adjust the balance of seasoning with a little grasshopper garum if necessary.

When preparing for larger numbers we cooked the clarification traditionally in a large stock pot.

At the Pestival event, we served alongside the roasted desert locusts.

photo: Wellcome Images

photo: Wellcome Images

Vinegar Science pt. 4: Slow Malt Vinegars with Nordic Flavours

Added on by Arielle Johnson.

by Arielle Johnson


Traditional malt vinegar, most commonly doused on fish and chips, is not regarded with much culinary interest. In our quest for developing Nordic vinegar, we found this widely produced, commercial malt vinegar as a source of inspiration for developing beer-base vinegars that held the potential for more complex and interesting flavors. The experimentation consisted of two types of malt-beer bases. For one, we mashed and fermented pale ale barley malt in a style similar to home-brewed beer. For the other, we brewed a koji-beer by creating a mash as if koji were malt. This method of brewing and fermenting koji proved unsuccessful, so we tried using another type of grain-based alcohol as our base. We created barley koji sake, which yielded much better results. To these malt vinegar bases we added flavourful foraged Nordic botanicals and allowed the vinegars to continue to slowly ferment for another 3-4 months.

After our descriptive analysis, we wanted to experiment further, especially with approaches to alcoholic fermentation and flavour addition. Could we better incorporate Nordic flavors like pine, liquorice, and juniper, as well as things like seaweed, which we have used at Nordic Food Lab for other flavour and functional purposes, into robustly-flavored, well-rounded vinegars with stability and aging potential?

The obvious next step was to explore a 3-stage process: a sugar-to-alcohol yeast fermentation, followed by the addition of non-fermentable, highly-flavoured ingredients (either during or after fermentation), and then a slow (3-4 month) passive fermentation into vinegar following the addition of raw vinegar as a starter culture.

Sugar and Alcohol

Initial ideas for sugar sources that could contribute a pleasant but not overpowering flavour to a vinegar, that would be available in the winter (in keeping with our interest in seasonality), and that would ferment nicely were apple juice and birch syrup. Apple juice could be reduced into a syrup through boiling, and then mixed with uncooked juice to reach a sugar level that would yield a relatively mild vinegar. Similarly, birch syrup, which has a much fruitier flavour than maple syrup, could be diluted to a comparable level. Both of these sugar sources, we reasoned, should provide, if not a blank canvas, then at least a foundation to begin showcasing other aromatic ingredients.

We were separately but simultaneously experimenting with an insect-hopped ale, and realized that beer malt was another near-perfect base for new vinegars. Relatively inexpensive, plentiful, covering a huge range of flavours (all beers, by definition, involve malt; the flavour range between, say, lagers, lambics, pale ales, baltic porters, and quadrupels speaks to the versatility and diversity of malting as a process), and fairly easy to work with, malt also allowed us to begin exploring vinegars made from more specialty beers. Traditional malt vinegar is one of the most widely-produced commercial varieties of vinegar, but despite its ubiquity on fish and chips, the commercial versions are not so interesting culinarily. This next-stage project would focus not on getting the cheapest vinegar out of malt, but exploring malt’s potential for producing and supporting complex and delicious flavours.



We mashed and fermented pale ale barley malt (augmented with a variety of other malts) in batches of 8 to 30L with techniques likely familiar to home brewers. Using some handy online calculators, we figured out how much malt we needed to obtain a certain sugar content. About 80% of malt mass can be converted into sugar, and somewhere between 60-90% of this sugar can be extracted out of the grain – which in turn yields a particular alcohol level and, after acetic fermentation, a particular concentration of acetic acid. We ground the malts in a grain-grinder, small enough for an efficient extraction but not so fine that the particles would mix with water and cause a ‘stuck’ or slow fermentation.

our mash tun

our mash tun

The malt and hot water were mixed together in an insulated container and held at a temperature between 64 and 69°C, where the amylase enzymes in the malt are most active, chopping long starch molecules into small sugars which yeast can metabolize into ethyl alcohol. At the lower end of this range (64-65°C), beta-amylases are more active, leading to higher proportions of disaccharides (called maltose), which are wholly digestible by yeast. At the higher end (67-69°C), a different form of the enzyme called alpha-amylase becomes active, and this indiscriminate digester of starch yields maltose molecules as well as many other larger oligosaccharides, called dextrins, which can contribute viscosity, body, and sweetness but are not digestible by yeast. As such, a slightly cooler mashing will yield a drier, higher alcohol beer, while a hotter mashing will produce a sweeter, more viscous, and less alcoholic beverage. For most of our batches we stuck to the lower range, but for a few we heated the mash up to higher temperatures at the end to get a bit more body and sweetness in our resulting vinegars.

Many times, projects that may seem new actually end up being reinterpretations of long-held traditions. In taking malt through the brewing process, for example, the question of to hop or not to hop invariably came up. For vinegars with a distinctly beer-like taste it would make sense to hop the beer, but we also wanted to make at least some vinegars whose flavours expressed the other aromatic ingredients along with the malt. A little research into the history of brewing shows that the un-hopped beers we made were actually much closer to the medieval and pre-early-modern version of ale, which didn't contain hops until somewhere between the 11th and 16th centuries. Totally unhopped, alcoholic malted grain beverages, at least in England, were called ales, to differentiate them from hopped versions imported from Holland, which were called beers. In fact, adding things like pine needles, juniper wood and berries, and other foraged herbs to the fermenting or finished wort actually reflects a much earlier style of brew called gruit (which often also included bog myrtle, mugwort, yarrow, and/or heather), or the still-popular Finnish beer sahti, made with juniper berries and filtered through juniper twigs.

At the same time that we were developing beer vinegars, we also started playing with roasting koji, which caramelizes the sugars in the koji and creates new flavours, similar to coffee or chocolate but definitely its own creature. Our friends at the Noma test kitchen put this to excellent use in a mole dish (a diverse group of sauces in Mexico, some of which involve cacao), and we collaborated on different ways to get roasted koji into vinegar – making alcoholic teas out of it, pine-vinegar-1.0 style, and also adding it to a beer mash with regular malt. By exploring different roast levels, ratios, and fermentation routes, we made koji-beers in a variety of colours, strengths, and flavours that then slowly, with the addition of foraged botanicals, continued on their way to becoming vinegars. For the recipe for Ben's first roasted koji pale ale, check out our post on roasting koji.

roasted barley koji

roasted barley koji

It seemed logical to also try brewing with barley koji directly, rather than as an adjunct to a malt fermentation. Treating the koji like a malt – mashing it with water at pro-amylolytic temperatures (64-68°C) – was unsuccessful, as it had quite a low yield and also seemed to induce some proteolytic action, producing a funky taste that wasn't altogether pleasant. Making a barley sake, on the other hand, worked quite well, and we're excited to see what acetifying this will lead to. Unlike the sugar extraction through mashing and heat involved in beer-brewing, that in sake-making involves Aspergillus oryzae grown on grain (in our case, barley) to make koji, which is sweet and full of amylolytic enzymes, and then mixed with cool water, more steamed barley, and yeast. The koji will slowly convert the starch of the steamed barley into sugar, and the yeast will metabolize the sugar as it is transformed into alcohol. Then, the sake is strained off of the lees of grain, mold, and yeast, and these lees – which still have some enzymatic activity – can be used for pickling (as in the traditional Japanese kasu-zuke, sake-lee pickles) or other purposes.

After brewing and fermenting the beers/gruits with yeast under an airlock, we began splitting the larger batches and adding aromatic ingredients, as well as starter vinegar, which we kept at 20% in order to control our comparisons from batch to batch. Each vinegar batch gets a cloth lid so oxygen can get in, and we are keeping them in a safe place until later, when we are planning to do a more formal sensory analysis.

Next up: Recipes



A side of bee larva with your afternoon coffee?

Added on by Edith Salminen.

by Edith Salminen

Bee larvae straight from our freezer.

Bee larvae straight from our freezer.

When a fellow researcher here at the Lab asks me whether I’d like to give him a hand doing field work for his thesis, meaning feeding random Copenhageners bee larva soup, I say “Ja tak!” 

Could there possibly be a better way to spend an afternoon?

Jonas Astrup Pedersen is the Larva-man. Now an almost-graduated Master in Food Science and Technology at University of Copenhagen, Jonas has been in and out of this rocking houseboat for as long as some of the oldest ferments downstairs. He is passionate about sensory analysis and experimentation, coffee and sourdough bread – really everything gastronomy. Being one of the only Danes on board, Jonas has been a wanted man these days, requested to address various food-related topics on Danish national TV and radio. Blood and gluten are some of the more recent ones. When he’s not busy doing public appearances that is, Jonas is keen on discovering how neophobic – or neophilic – Danes are in their foodways. Ever since November, I’ve been sitting across from him at the Lab watching him meticulously busting his brain for his master’s thesis on unravelling how people perceive and accept novel foods, using bee larvae as a case study.  The Lab for him – as for us all – is both his playground and safe-zone for quirky and delicious experimentation. Stepping out from this inspiring and encouraging cradle can sometimes get rather knotty. 

Almost ready for service.

Almost ready for service.

“If we manage to get 70 people to try the soup today, that would be great,” he says with his characteristic grin, as we start prepping the vegetable and bee larva soup in the morning for our first service. It says ‘VISIBLE LARVAE’, ‘INVISIBLE LARVAE’, ‘NO LARVAE’ on a sheet of paper next to the cutting board on the stainless steel island. Three soups, one base recipe with three slightly different variations. Will people want to see the larvae as they savour the soup, or is ignorance bliss? Will the bee larva flavour be a sought-after twist to a perfectly acceptable but otherwise banal veggie soup? Let’s see.

By now, two months into my internship at the Lab, I’ve learned to recognize the very distinctive smell and flavour of the fatty little creatures: nutty and buttery, sometimes even mushroomy, and to me much like this ubiquitous Swedish “liver” paté that comes in a tube (super addictive). I’ve only had them straight up deep frozen and in Jonas’ soup, but Josh describes fresh and alive bee larvae as something close to fish roe in texture, very delicate and “fucking delicious” in flavour. Listening to Josh’s description, I got the oddest urge to pop one of those alive babies in my mouth. Deranged? Totally, but also far from it. Talking about how bee larvae burst against one’s palate… I can but smile, stir the soup and see how the tasty little suckers float around in creamy veg stock together with carrots, celeriac, leek and onions. The whole boat smells of sautéed bee larvae. Yup, very distinctively bee larvae indeed. And we love it.


Off to the larva-mobile!

The Larva-man has chosen to do his guerrilla soup tasting at three different locations in order to reach the maximum variety of people. This excites me. Not only do I get to see Copenhagen’s many sides, but I’ll also get the chance to observe different people accepting or refusing insects as an edible food item. The socio-anthropologist in me is on alert. 

Jonas working his charm on one of our first guests at Spinderiet.

Jonas working his charm on one of our first guests at Spinderiet.

First up, a suburban square by Spinderiet mall in Valby, a 15 minute bike ride away from the centre of Copenhagen. Valby is a kind of grudgy neighbourhood further west from the hipster central Vesterbro. Second stop, the humongous shopping centre Field’s erected in the middle of nowhere, on a field, hence the (not very original) name. At Field’s you get all kinds of people, students, teenagers, families, locals and foreigners: a mish-mash of people living in Copenhagen for different reasons. Last stop, Torvehallerne right by Nørreport station. This bourgeois-bohème indoor market is where the well-off Copenhageners buy their (very expensive) food. It’s also a favourite amongst tourists. Of all three locations this is surely the most foodie-like of them. Our presumption is that the higher socio-economical status might correlate to an increase of the acceptance of our experiment. 

“These are places where we’ll find normal people,” Jonas explains. “Normal people” are a rare breed here at the Lab where the next person stepping on board this mad, floating research centre is probably somehow loonier than the previous one. We often forget about “those other types of people” who might not, with immense appetite and lust for umami, attack a container filled with more or less mashed and rotten edibles or, for that matter, a fragrant bowl of bee larva soup. We didn't really discuss this potential challenge beforehand, but we certainly expected to be confronted with it to varying degrees in the different locations.

Jonas and I head to the first location right after lunchtime, our car loaded up with our three steaming soup pots. I wonder how many Danes will choose a side of larvae over a kanelsnurrer with their afternoon coffee? As my Danish is not quite there yet, I told Jonas I’d do the people hunting and lure them in for him to feed them larva soup. Game on. 

(Click through the photos below of some of our intrepid participants)

How hard could it be?

The table is set.

The table is set.

Spinderiet. We definitely overestimated people’s will and courage in trying novel foods. “No thanks, I’ve got a chewing gum in my mouth”, “I just ate”, “I’m vegan”, “Why would I eat bugs”, “Are you crazy”, “ I have no time for such nonsense”, “No time, sorry”, “Oh no, insects, no, no, I thought it was free coffee”, “No thanks, I’ve got a girlfriend” were some of the reactions I got approaching our potential targets. At the Valby mall women especially did not like the idea of a bee larva soup dégustation on this crisp winter afternoon. On the other hand when I, as a woman, challenged young and middle-aged men to try Jonas’ soup, asking them if they’re “man enough”, they obviously couldn’t say no. It proved to be a good strategy and we got a decent number of hits with this method. Nevertheless, my utmost respect goes out to a mother of two boys, I’m guessing a 5- and a 9-year-old, who didn’t hesitate having a fun and educational pit-stop at Jonas’ soup shack. What a cool mum! And the boys loved it too. 

Field’s. Damn, even harder than the previous location. People at Field’s were on autopilot, wired to their smartphones, impossible to be reached and couldn’t be bothered to take part in our wacky arthropodan experiment. It seemed as though the “normal people” at Field’s that cold and grey afternoon had no interest in “new foods”, and as a matter of fact, using those two words in the first sentence of approach was not the way to go. Enquiring “Have you ever eaten insects before?” had a slightly better effect, but still didn’t do the trick. Frustrated, we had to face the obvious: people were just more neophobic in this part of town. Third time’s the charm, we thought. However well one prepares for such fieldwork, trying to reach out to a maximum number of people across the maximum range of a crowd is a real Rubik’s cube.

The Lab bike parked at Torvehallerne. 

The Lab bike parked at Torvehallerne. 

Torvehallerne. “Foodies” and gourmands pilgrimage here for quality food. Also a lot of tourists come here to savour the “chic and pure” taste of Copenhagen – the perfect crowd for our fieldwork. Of course, it had to be the coldest day so far this winter. Typical. With icy wind and snow freezing to the core, we had our doubts about how well it could go. We served the soup out of our very cool Lab bike right outside the entrance to the market. Whether it was the weather or the slow Monday, we didn’t have the same stamina in our approach. However, to our happy surprise, people actually came to us. The ‘Nordic Food Lab’-branded bike surely helped in attracting curious eaters. Not only did people want to try the soups, but they were keen on learning more about insects as food. We had the privilege of feeding an Austrian noma chef, a professor of landscape architecture (and his gorgeous 1 year old Samoyed doggie too), a group of business school exchange students from Australia, just to name a few. All in all, Torvehallerne was the most fruitful of the three locations.


(Don’t) Stop bugging me

Close to a hundred people accepted the challenge of tasting Jonas’ bee larva special, keen on trying a novel ingredient with potential for expanding cuisine. Unfortunately, at least the same amount, if not more, bluntly declined. For some reason, men were more prone to savour the soup than women were.  An observation that made us hopeful was that kids and teenagers seemed more curious and keen to eat the larvae. Could it be they are more open and have a different attitude to the future, or just a battle of gaining coolness points by doing something outrageous? Let’s be positive and go with the first idea. Quite a few elderly people proved to be gutsy too, even though most were hard to convince at first. They were definitely more open to spare us ten minutes out of their busy schedules than others. Yet if we only managed to hold people's interest while presenting our motivation in a few sentences, it opened up a window in most people’s minds for what they might consider food. It also proved easier to attract couples or small groups. Peer pressure and/or encouragement from loved ones also seemed to make it easier to accept and grasp what we were trying to do. 

"Normal people" at Field's.

"Normal people" at Field's.

(from R to L) Me, Jonas, and one of our most enthusiastic participants at Torvehallerne. Thanks for the photo, Alex!

(from R to L) Me, Jonas, and one of our most enthusiastic participants at Torvehallerne. Thanks for the photo, Alex!

Most importantly, these taste experiments in the field made us reflect on how crucial it is to not forget about all the “normal people” out there. Whether it’s about them having different tastes or a less-strong attraction to the new and unusual compared to the people in our immediate surroundings is a big question worth thinking about. What is usual here at the Lab is often weird and disgusting for many folks out there. Doing what we do is exciting and fun, at times both dippy and inspiring – but if we fail to reach out and convince others unlike us to at least give some of these foods a try, what is the point in the long run? After all, our ultimate aim is to share our food and ideas with everyone, not just preaching to the choir or worse, fuelling a load of foodie onanism.

In the car after our third and last guerrilla soup run, we drove in silence. I think both Jonas and I had a lot on our minds, many impressions and many questions without simple or straightforward answers. As we parked the car outside the Larva-cave, we glanced at each other and smiled. We both knew… we’re lucky to be where we are and this experience was a much needed reality check. We need reminders of the fact that there’s a whole world out there to reach in order to make people look at bugs – or seaweed, or microbes, or any other neglected or underutilised ingredient – and go, “Yum, I’ll have that for lunch." For us, it is the kick we need to give all of this madness a real purpose.

Hop into it

Added on by Justine de Valicourt.

by Justine de Valicourt


We did a lot of different things to hops. Some worked, some didn't. An exploration of the life of Humulus lupulus beyond beer.

When people ask, we say the lab is funded by independent foundations, private businesses, and government sources. This is true; though really, we should start saying producers, passion, and the sheer generosity of people.

Dernière importation - 1.jpg

We recently asked a hops supplier from Germany to send us 2 kg of two kinds of fresh hops to experiment on the curing process and the effects on beer taste. Our aim was to investigate flavours in other ways of preparing hops than the conventional quick-drying method. Yet instead of 2kg, we received 12 kg of each variety. 24 kg of fresh hops is a lot. A – lot. We don’t think this was a mistake, because we received even more a few days after. Beyond the fact that the lab smelled like legal cannabaceae for days – as did our urine – this free flood of hops was a great creative challenge and pushed us to investigate not only the drying process, but also their molecular composition and culinary potential. For two weeks, we almost stopped every other project to be able to process and use this mountain of hops.

I will reveal the punchline up-front: hops are terribly bitter and most of our recipes turned bitterly bad. But gaining this knowledge is indeed the aim of trying.

Contrary to what many people think, Nordic Food Lab is small. The team currently varies between 4 and 8 researchers at a time, depending of the season and the day of the week. This small scale and loose structure permit us to impose few limits on our thoughts. The team is formed with people with different backgrounds and strengths, but we are all curious. And we like answers.

Receiving 24kg of hops, or 40kg of herrings, or 150kg of quinces fuels our drive for knowledge. What to do with all this? How to keep it? How to make it delicious? Sometimes it is not the quantity but the thing itself that poses a creative challenge. What should we do with a very smelly beaver or just a tail of one of its fellows? Or with kilos of green, unripe plums?

It's Christmas at every funky delivery. First, we look, then we smell, and, when possible, we taste it raw. For some ingredients, these first steps are enough to bring an idea that will take care of all of it. It was the case for the green plums: we tried different ways of curing them as if they were fresh olives. Some turned out awesome – a little acidic and crunchy, definitely delicious in a salsa verde or with a beer.

Dernière importation - 3.jpg

The hops were more difficult. Before receiving them, we had never heard about hops in anything other than alcoholic beverages. Knowing that hops are in the same family as marijuana and hemp made things easier. There are a lot more how-to-get-stoned-with-cannabis recipes out there than ones that use hops beyond brewing. Part of our conclusion was to not use the hops as a main ingredient, but rather as a subtle spice. Hops give a lot of flavour even in very low concentrations. The bitterness is also easier to manage in fats than in water, partly because the α-acids are hydrophobic, so the essential oils containing all these acids cannot be washed from the tongue with water. Oils and fats bond with the bitter molecules, preventing them from interacting with the taste buds. In other words, if those acids are mixed in oil, they are going to have less interaction with the tongue cells because they will stay 'attached' to the fatty molecules, and so the taste won't be as potent as if they are in suspension in water.

We tried many many recipes.

A hop mayo was awful, as were all things involving infusion into water: soup, tea, etc.

We also tried to lacto-ferment some, as we do with almost every new ingredient we get. Didn't work. Hops, as we already knew, inhibit bacterial growth (Simpson, 1993), especially lactobacilli, the bacteria responsible for wild lacto-fermentation, and beer spoilage.

From our research on marijuana, we decided to try butter, but preparing from scratch, using the hops to both infuse and culture the cream. We tried cold and warm infusion at 10% w/v. Don't try the warm version. The cold infusion was fine, but nothing outstanding: a butter that tastes like hops.

We also found a recipe for hop and potato sourdough and made a bread from it. The result was a beautiful crusty bread with a nice texture – but the taste was the worst ever for a bread.

Dernière importation - 5.jpg

Yet there were some recipes with real potential. One was a gravlax exchanging the traditional dill for hops – fragrant and complex. Another discovery was grapeseed oil cold-infused with hop for few minutes – it turned out to be very fruity, green and with a little pinch of spiciness at the back of the throat, similar to some extra-virgin olive oil. We tried this technique with a variety of hops called Herkules, an infusion of 30 minutes with a concentration of 10% (10 parts fresh hops, 100 parts oil). Better results could probably be obtained with other hop varieties with lower alpha-acid content. Next season we will try with the wild hops we foraged in Christiania (yes, it's hops, so nothing illegal).

We inoculated them with food-grade moulds: Aspergillus niger and Botryotinia fuckeliana. A. niger occurs in the process of making Pu-erh tea, but didn't bring anything interesting to the hops, just some oxidized aromas. Botrytis, however, gave us something worth talking about. B. fuckeliana is also called noble rot, the fungus that infects some grapes and permits the famous Sauterne wine, among others. On the grape, Botrytis concentrate the solids (sugars, minerals, fruit acids) by making holes in the skin, allowing some of the water to evaporate. On the hop, by unknown means, it developed fruity and citrusy aromas. Further investigation has to be done to use these nobly-rotted hops in different kinds of beverages and food.


We had some leftover still sweet elderflower wine. We cooked it briefly to stop the fermentation and added hops (10%, cold-infused for 1hr) and kombucha mother. It turned out better than the wine by itself. We also made a hopped cherry wine, a hopped cider, a hopped malolactic fermented cider, and brewed a half apple juice half malt beer. All of these alcohols are quite interesting, some are even gaining some complexity with time, and even if they are not outstanding yet, they are a first step that could be taken further by others who know more about brewing and alcoholic beverages.

We brainstormed about how to make acceptable the strong bitterness that came with all our food trials, and decided to go for sweets. We made two types of toffees, both traditional recipes from Quebec. I guess we Quebecois have a sweet tooth. The first is called ‘Tire Ste-Catherine’ and is a smooth toffee made from sugar, molasses, water, vinegar, something alkaline and a few other things. It is pulled for a while when still warm and turns golden. We cold-infused the hops in water (10g of fresh hop/100mL of water) and the final flavour was interesting. Just hoppy enough to add some complexity to the taste and balance the sweetness.

Dernière importation - 2.jpg

The second recipe is more hoppy. We cold infused hops in cream (10g of fresh hop/100mL of cream) and forgot about it for more than a week. We finally used that cream to make ‘Sucre à la crème’ or Scottish tablet. In Quebec, it is a toffee traditionally made from maple syrup, cream and butter. Without the maple syrup, it can easily be done with brown sugar. The recipe is 1 parts cream hopped cream, 1 part of fresh cream, 6 parts sugar/syrup and 1 part of butter. Cook it until it reaches 118°C, let it cool down without disturbing until 50°C, then whisk and pour into a mould. At the whisking step, one can also add some nuts. Cut before it cools down completely. The whisking process brings seeds of crystallisation and makes the final texture sandy and moist at the same time, without sticking to your teeth. Miam! Is it better with hops? I'm not sure, but it might be more interesting to pair with coffee this way. Doing the same recipe with proper maple syrup and cream a little less infused hops would probably turn out even better.

No more bitter-sweet for now. Further directions include exploring some of the more aromatic varieties from Australia, New Zealand, and the US, investigating different types of bitterness (co-humulone is often thought to give a more rough bitterness at the end, for example), and looking deeper into different techniques for oxidation. One of our collaborators at the Jacobsen brewery has even told us about an experimental German variety he has with 0% alpha acid – that’s exciting. In addition, in the coming months we hope to smoke food with the hops along with wood chips, make new trials with alcohol infusion, and perfect the hop oil.

And even with all these trials, our freezer is still full of dried hops. Any ideas are welcome.

Vinegar Science pt. 3: Sensory Analysis

Added on by Arielle Johnson.

by Arielle Johnson


With all of these techniques being put to the test, comparison is needed to to determine whether the different vinegars are interesting enough for future elaboration. In this third instalment of our 5-part miniseries on vinegar science, we detail the process of sensory analysis – including assembling a trained human panel, generating flavour descriptors, identifying reference standards, and conducting replicate sets of tests – that we used to qualify their specific characteristics and perhaps to reveal which processes had led to a tastier result. Overall, it seemed that the vinegars that had ended with some residual sugar and had undergone more stages of fermentation yielded tastier vinegars.

While we taste all our experiments carefully and mindfully, we decided for this vinegar-investigating project to use descriptive analysis to profile the flavours of the vinegars. This meant that we could get some hard data to work with, and also explore how best to incorporate sensory analysis techniques into our ongoing research and development. We performed descriptive analysis on our vinegars at the University of Copenhagen (KU) Faculty of Life Sciences in Frederiksberg, with the help of a trained panel of ten volunteers from the food science department. The goal of this analysis was to pinpoint specific flavours, fix their definitions to real references, and determine the intensity of each flavour in a set of products.

The key components of a descriptive analysis are:

- The samples in the experimental set: Are they very similar or very different from each other? Small differences will be more difficult to detect but may yield more specific and less obvious information about flavour. Our samples were somewhat similar as they are all vinegars, with many of their flavour differences coming simply from differences in their primary ingredients.

- The panel: Human beings used as analytical instruments, reporting on what flavours are present and at what intensities.

- Flavour descriptor generation: The panel is both the tool and the process by which sensory analysis determines what flavours are present and prominent in a set of samples. This begins with panelists tasting the samples blind, thinking about what they perceive, and discussing them with each other, which leads us to:

- Terms and references: For every flavour the panel says they perceive, it is our job to create a reference that captures a consensus definition for each aroma. For example, when a panelists says “citrus", does she mean lemon peel or orange peel? Or something that only exists as a mixture of different fruits? We need to figure out the ideal combination that will then serve as a reference standard to keep all panelists based in a shared olfactory vocabulary.


Along with the taste descriptors sweet, sour, salty, bitter, and umami, we narrowed the list of flavours down to “red berry”, “strawberry”, “acetic acid”, “rotten fruit”, “chemical”, “green apple”, “liquorice”, “yeast”, “wine”, “tropical fruit”, “rhubarb”, “celery”, “earthy”, “green vegetable”, “citrus”, “pine”, and “blue cheese”. Creating references for some of these were pretty straightforward. Everyone agreed that the descriptor “strawberry” was perfectly captured by a ripe strawberry, cut in half.  But what about less precise terms? Rotten fruit – according to the panelists – did not smell like a fully rotten apple, but was more oxidized and fermented than just a bruised apple. Cubed, bruised, and yeast-sprinkled apples and pears, left to sit on a counter for a day, we finally agreed, captured the aroma the best. Dry yeast was too weak for the panel, but a cube of fresh yeast was perfect (since Danes tend to use this variety for baking, it was likely more familiar to our local panelists). For “red berry”, which the panel insisted was different from strawberry, neither red currants nor raspberries alone were quite right, but satisfied when combined together. The "chemical" aroma the panel was picking up on was probably ethyl acetate, a common by-product of vinegar fermentation formed from the reaction of ethyl alcohol and acetic acid; for this, nail polish remover was a good match. For “pine” and “earthy” references I gathered samples from the Assistens cemetery in Nørrebrø. Who knows, maybe they imparted a few molecules of Hans Christian Andersen, who is buried there, for good luck.

the references, with watch glasses on top to keep the smells from dissipating

the references, with watch glasses on top to keep the smells from dissipating

With the references prepared and agreed upon, we began the descriptive analysis proper. For 3 days in a row, the panelists smelled the references to reacquaint themselves with each aroma and its specific descriptor, and then went into isolation booths, where they smelled and tasted each of the vinegars and then rated the intensity of each of the reference flavours in the samples.

These pooled intensity ratings make up the flavour profile data we use to analyze the sensory characteristics of the vinegars. Certain statistical techniques we apply to this data determine which flavours are most useful for distinguishing samples from each other, while other techniques look at the sensory data holistically, and compare it to the flavour-active molecules present in each vinegar, to describe the sensory and molecular drivers of flavour across the dataset as a whole. This analysis will be made available in a forthcoming journal paper.

The sensory and chemical analyses we performed on our vinegars give us a glimpse into how their component flavours interact. By continuing to borrow analytical techniques from academic sensory and flavour chemistry labs, we look forward to building a molecular intuition about flavour to complement the intuition of our palates. But when it comes to the answers we seek, and their questions, the scientific process will only reveal so much. To fully understand food, we need also to listen to our palates in more aesthetic, less quantitative ways. For example, some of us around the lab, and some of the panelists, talked about differences in balance, complexity, and depth of flavour, which are difficult to measure analytically. We can develop our culinary empiricism to deal with these ideas faster and better not only by taking into account whatever hard data we might have, but also by contemplating and making decisions on the most compelling directions to pursue using our own senses.

Many of the most interesting questions that arose while we developed our vinegars had little to do with naturalist, analytical ideas of underlying flavour chemistry and more to do with practical concerns about what we can do with these ingredients, the best ways to work with them, and how to make products that are new and interesting and better than what we already have.

For example, it seemed like some of the tastier vinegars were more complex and had gone through multiple fermentations (for instance, a yeast fermentation followed by an acetic fermentation). On a molecular level, this theory makes sense: each fermentation step will generate more and different volatile molecules as by-products, leading to a greater potential pool of flavours. Furthermore, starting from a sugary mixture and fermenting it into alcohol with yeast means that some residual sugar might be left over – balancing some of the acid, giving a bit of body, and improving the overall flavour. At the same time, some of the tea-based vinegars had interesting flavour potential but at times seemed to lack complexity. We also wondered if the air-pump approach to running the acetic fermentation – which was especially good for rapid prototyping as it produced workable vinegars in under a week – led to any flavour differences, good or bad, compared to a slower, passive fermentation over the course of months.

Next up: Slowing down the process, and expanding from wine to beer.

Dream Christmas Cake

Added on by Guillemette Barthouil.

by Guillemette Barthouil

Dreams are in season. Days blur into nights,

the northern darkness plays with our minds.

We awake with cake: our dreamed christmas cake –

a midwinter feast to celebrate the light.

Longer days – a taste

of what has and is to come.



We have had one of our whiteboards emblazoned for months with the phrase “DREAM CHRISTMAS CAKE” and filled upwith all sorts of related brainstorms. Then, in late fall, the Sustainable Food Trust asked us to make a dessert for a conference they were organising in London entitled ‘True Cost Accounting: Food and Farming’ – a key issue in our current food system. The event was to be held in early December. It was close enough to Christmas: time to actually make the cake we had been dreaming up for months.

Traditionally, much of the food eaten at Christmas is preserved in one way or another – dried, cured, smoked, fermented, combination thereof. But what about making the cake itself the way of preserving? English Christmas puddings, cakes, and mince pie seem to have evolved from the same fifteenth-century process of preserving meat [1]. In autumn, when fodder was dwindling, farmers would slaughter the surplus livestock. The meat was then preserved in a pastry case and mixed with dried fruit to prevent spoilage. Over time, dried fruits have become the main component of the sweetened pudding, with suet reminding us of its meat-based history. The alcohol component has been present at least since the 19th century, when Christmas pudding and cake as a dessert rather than a savoury course ('Christmas pottage') emerged as the now traditional dish [2]. It is likely, though, that alcohol appeared in prior recipes, for its abilities to enhance both preservation and enjoyment. British gentlemen (including our beloved head of research and development, a Scot) will tell you that the best puddings are at least one year old, the best being considerable older, doused in alcohol every once in a while to preserve it. Bloody English. [ed. – It should be noted that the author of this post is herself French – enough said.]

As we began to experiment in the kitchen, we started to favour pudding over cake, for its flavour, texture, and pliability. Then, in trying to source ingredients from our landscape while keeping the taste identity of a Christmas pudding, we slightly adapted the classic recipe. We adopted bone-marrow over suet for its delicate yet meaty and distinctly umami component. The liquoricey, clovey, and mineral notes of beet molasses allowed us to forego spices in the mix, while giving the pudding a beautiful dark colour. The addition of a nice dark beer only enhanced the deep, bittersweet, mineral flavour profile of the pudding. Working with the concept of preservation we also decided to make our own raisins. We lacto-fermented grapes – in brine with 2% salt – for 2 weeks and then dehydrated them at 40°C. This process gave the grapes a dried fig taste that fit perfectly with the pudding.


NFL Christmas pudding

100g bone marrow
20g butter
110g breadcrumbs
60g wheat flour
1 tsp baking soda
225g beet molasses
110g raisins
60g dried lacto-fermented grapes
275g dried blackcurrant
1 grated pear
2 tbsp brandy (we used oaked apple cider brandy)
75ml Dark Christmas beer
2 eggs

Freeze the bone marrow. Grate.

Weigh the breadcrumbs, flour and baking soda. Blend with the grated bone marrow.

Melt the butter over low heat. Weigh the molasses. Add them to the mix.

Weigh the dried fruits. Grate the pear. Add to mixture.


Mix the eggs, brandy, and beer. Add to mixture.

Blend the ingredients thoroughly. Cover and let the dough rest in the fridge overnight.


The next day, press the dough into a stainless steel bowl. Wrap and steam for 8h in a combi oven.

After the pudding is cooked and cooled, pour brandy over. Depending on how much in advance you make your pudding – and how alcoholic you like it – you can repeat this process as many times as you like.

credit: Nicola Robecchi

credit: Nicola Robecchi

The result was a rich and beautiful pudding, waiting to be paired with the freshness of a fruit. A poached pear seemed like the perfect accompaniment; classic.

Too classic. At this stage, we got stuck. Nothing really sang. We couldn’t find the thing that would make us jump to the next step.

One day, our microbiologist friend and mushroom expert, Sara Landvik, was at the boat for lunch. After lunch we served a version of the dessert for critique, and together we tried to talk it through. All of a sudden Sara said “you should serve it like a mushroom!” That was just the leap we needed. The rest is history.

A pear, poached in a syrup of elderberry, dried chanterelle and labrador tea. Fruity, fragrant, and terpinous as a walk in the woods.


Poached pear

Choose a round-shaped pear variety – we chose Williams.

labrador tea

labrador tea

Peel, cut horizontally into two equal parts and carve out the inside with a melon baller, leaving edges of around 0,5 cm. With a turning knife remove the stalk and the calix end of the fruit.

For the syrup, boil 1L of water with 100g of sugar and 100g of elderberries.

10 minutes before poaching the pears, add 15g of dried chanterelles and 5g of labrador tea, Rhododendron tomentosum.

Strain the syrup and poach the pears for 10 minutes.

Once poached, remove the pears and reduce the syrup to a fifth of its original volume. Pour the syrup over the pears so they become bright red.

credit: Nicola Robecchi

credit: Nicola Robecchi

Stuff the pears with approximately 30g of the soaked Christmas pudding, shaping it with your finger as if it were the stalk of a mushroom supporting the fruiting body of the pear. The pudding should stick out of the pear about 1 to 2 cm. One pudding should yield enough for around 50 mushrooms.

credit: Nicola Robecchi

credit: Nicola Robecchi

Cheese dots

Take 150g of Stichelton cheese (delicious English raw milk blue cheese), mix it in a thermomix with 150g of cow cream 38% and 1,5g of Xanthan. You should obtain a soft yet solid paste with a mild flavour of Penicillium roquefortii.

Fill a pastry bag, cut 3 mm off the end and create dots of cheese on the poached pear, transforming it into the classic fairytale mushroom, Amanita muscaria, the fly agaric.

Amanita muscaria

Amanita muscaria

Like children dancing around the Christmas tree, we were super excited about our wild mushroom Christmas pudding. Tasting, critiquing, finding new ideas and pairing - we tried and tried again. Though something was still missing. What did we want to eat most when we were playing in the forest as kids? What lies under the underbrush, the result of fungi digesting and mulch compacting, the foundation of the forest? Earth; of course. Mother Earth.

Edible soil

200g wheat flour
120g butter
140g beet molasses
200g toasted hazelnuts coarsely grounded
30g finely grounded toasted koji
10g porcini powder
1 tsp baking soda
2 eggs


Mix the flour, hazelnuts, koji, porcini powder and baking soda together.

Melt the butter over very low heat.

Add the butter, beet molasses and eggs.

Mix the ingredients together, working the dough as little as possible.

Spread on a baking sheet approximately 0,5cm thick and cook at 160°C for 20 minutes.

Once cooked, dehydrate the cake overnight in a dehydrator or in the oven at around 45°C.


credit: Nicola Robecchi Sweet Amanita Victorian plum pudding with bone marrow and berries, poached English pears, Stichelton cheese and edible soil.

credit: Nicola Robecchi
Sweet Amanita
Victorian plum pudding with bone marrow and berries, poached English pears, Stichelton cheese and edible soil.

Oh Sweet Amanita!

Pick the right one, enjoy your trip and see you in the new year!



[1]  Black, M. 1981. “The Englishman's Plum Pudding” in History Today, Volume 31, Issue 12
[2}  Davidson, Alan. The Oxford Companion to Food. Oxford: Oxford University Press, 2000. p.184-5.



Roasting Koji

Added on by Josh Evans.

by Josh Evans


Finished koji smells amazing. It is fruity and floral, with an underlying hint of fresh mushrooms. And it changes depending on the substrate: rice and quinoa give a nuttier aroma, sunflower seeds and buckwheat are more earthy, and beans give a smell that is entirely savoury.

At the beginning of this year, we began thinking of how we could broaden this flavour spectrum even further. Maybe it was the zeitgeist in our little family at the time – Rosio in the noma test kitchen began to roast the koji and it gained an entirely different flavour profile. When we began doing the same on the boat, our first method was to roast the loose grains at 160˚C for 30-40 minutes. The koji became deep and rich, with aromas reminiscent of chocolate, coffee, caramel, and toast. Some of our trials retained hints of their original fruity and floral aromas. The potential was great.

We began treating this new ingredient in a similar way to its flavour companions. 
Taking Rosio's lead, we infused it into cream (1 part koji : 2 parts cream) overnight, and passed the thickened mixture through a sieve the next day which yielded a rich, ganache-like substance.


We brewed the ground grains into coffee (more work is needed). We stirred some fine powder into heated milk and chocolate for a more complex cocoa (admittedly more of a treat than an experiment).


Over at noma, it has found its way into a variety of dishes and projects, from the Potatoes and Bleak Roe to the Seaweed Danish. Definitely a versatile ingredient.

It also became a crucial pairing with pork’s blood in many of our intern Elisabeth’s recipes for blood as an egg substitute in baking. The minerality of the blood meshes well with the caramel and Maillard notes of the roasted koji, and one of the successes of that project (in my eyes at least) was a recipe for ‘chocolate’ ice cream with blood, roasted koji, no chocolate, and no eggs. Details forthcoming.

The similarity to malt was undeniable, and Ben started using it to make syrup extracts and to brew beer. At first, the beer trials seemed to lack body, but after some months of aging they are starting to develop into something quite good. We’ll be taking this one further for sure. In the meantime, here’s our first recipe.

Ben’s Toasted Koji Pale Ale

Volume:      28 L
OG:           1050
FG:             1025
Alcohol:      3.3% but we had problems with attenuation
IBU            39
BU/GU       0.78

Maris Otter Pale Malt    5634g
Roasted Koji                 1000g

Mash schedule:
66­68°C / 60 minutes, 71°C  / 35 minutes (during continuous sparge) 

Summit                    17.4% alpha      20g   90 minutes
Saaz                        4.4% alpha        33g   15 minutes
East Kent Golding   5.85% alpha     16g    10 minutes
East Kent Golding   5.85% alpha     22g    5 minutes

Yeast: WLP500 Trappist Ale
Fermented at 18 degrees C for 30 days.
Bottled conditioned with 7g/L of sugar although still quite dense
Needs time in the bottle to improve.

We are not experts in beer making, and so working out how much roasted koji to put in this recipe was really just instinct; however, the result is good. There are problems with attenuation, like how much sugar is left in the beer, but the taste is good, and improving with age.


We recently became more curious about the roasting process and decided to go back to basics to better understand our options, creating a sensory trial with samples varying temperature and time. We roasted batches of 300g at 140˚C, 160˚C, 180˚C, and 200˚C for 20, 30, 40, and 45 minutes. We then let the samples rest for two days for some of the most assertive burned or over-roasted flavours to dissipate, then we ground them in the thermomix for 10 seconds at level 7. We added 60g of the ground koji to 120g of cream, and vacuumed the mixture to 96.5% to infuse overnight. The next day they were warmed in a bath for around one minute to return the mixture to a fluid state. Samples were tasted with small spoons and included the ground koji in the cream.

Sensory evaluation by lab members yielded the following results.


20 min   fruity with some chocolate notes. Very koji-y. tropical, passionfruit.

30 min   less flavourful, creamier

40 min   little burnt taste at the end, dark chocolate at the end

45 min   more burnt, little coffee-y

160˚C   very oily

20 min   acidic, burnt, like bad coffee… very oily

30 min   more coffee-y, harshness like 100% cocoa chocolate

40 min   toasted breadcrumbs, burnt, maybe good in small amounts

45 min   just burnt

180˚C   also very oily

20 min   interesting, in between green coffee and burnt, more pleasant coffee acidity, green leafy vegetalness

30 min   bitter burnt caramel

40 min   just burnt

45 min   ashes


20 min   burnt with koji fruitiness, between chocolate and coffee with slight caramel, uneven toasting

30 min   acidic and burnt

40 min   very unpleasant, way too much toast

45 min   too much toast

One of the lab members also thought the 140-series smelled very savoury, like fermented soy-style sauces, while the 160-series gained more of the chocolate/coffee notes. The 180-series was pretty variable, with the lower times having bitternesses bordering pleasure and distate, while the 200-series was pretty much inedible, although there could be some possible applications of a quick blast with high heat.

Overall, the mid-160-series came through as a stronger roast, with the 140-series generating gentler and more diverse aromas and the shorter end of the 180-series also holding potential for further exploration. 

We are excited by this wealth of unexplored possibilities. Further directions include refining its use in beer (we also used some in ‘Wormhole’, our ‘oatmealworm stout’ designed with Siren Craft Brewery for our Pestival menu in April/May), and developing recipes for a Nordic chocolate and a Nordic coffee using wild plants, fruits, roots, and other botanicals. In the meantime, I’m fine eating the ganache straight with a spoon.


Koji – history and process

Added on by Josh Evans.

by Josh Evans


Koji is our lifeblood. It is the basis of many of our fermentation experiments, the functional backbone of our pursuit for diverse flavours and umami taste. This post reviews its cultural and evolutionary history, and describes our technique for producing koji at the lab.

The basics

Koji (kōji in Japanese, qu in Chinese, nurukgyun in Korean) is a culture made by growing different fungi on cooked grains or legumes in a warm, humid place (Shurtleff & Aoyagi 2012). The koji moulds produce many enzymes, including amylases, proteases, lipases, and tanninase, that break down (hydrolyse) macromolecules like starches, proteins, and fats into their constituent parts, such as dextrin, glucose, peptides, amino acids, and fatty acid chains (Chen et al. 2008). These simpler substrates provide nutrition for cultures of yeasts and bacteria that come in subsequent fermentation stages (Mheen 1972). The cultures are ancient technologies used to produce a variety of fermented food products, including soy sauces, jiang/miso, fermented black soybeans, and grain-based wines like sake, amazake, and li (Shurtleff & Aoyagi 2012). The most frequently occurring microorganism found in koji production is the fungus Aspergillus oryzae, but there are others that also occur, including A. sojae, A. usami, A. awamori, A. kawachii, Rhizopus spp., Monascus spp., Mucor spp., and Absidia spp. (Murooka & Yamshita 2008; Chen et al 2008).

There is a diversity of methods for koji or qu production around East Asia, using different microorganisms, wild or inoculated sources, mixed or pure cultures, and a variety of substrates. This diversity can make mapping the relationships between the different analogues tricky. For example, in English the term ‘koji’ has come to stand for all members of the family of grain-based saccharifying fermentations involving A. oryzae and related organisms, even though the Japanese word kōji refers to only one subset of the larger group of more or less loosely related cultural analogues. Korean nuruk, for example is used for making rice wine, while meju is the one used for protein-rich fermentations. Chinese qu alone encompasses a breadth of fermentations involving different substrates such as rice, sorghum, wheat, barley, peas, or soybeans, different microbial species of the genera Aspergillus spp., Rhizopus spp., Monascus spp., Mucor spp., and Absidia spp., and different techniques such as keeping mixed cultures, using various wild sources for microbes, and making the qu in loose or different pressed forms (Chen et al 2008). This diversity is in turn spread across widely different geographical areas. We generally use the Japanese word ‘koji’ to refer more broadly to the class of grain-based saccharifying fermentations involving A. oryzae, while recognizing the multitude of both different traditions and words used to describe them – this decision is mainly due to the historical introduction of the concept and word into English from the Japanese, as well as our process with koji-making starting with an eye to exploring Japanese fermentation traditions; since then, we have begun exploring some Korean and Chinese techniques as well.

To illustrate the point, here are a few examples of different qu preparations:
Hong qu – also known as ‘red yeast rice’ or ‘red fermented rice’, fermented with Monascus spp., in loose form
Xiao qu – from south China, made with rice and rice chaff, fermented with Rhizopus spp., pressed into an egg-shaped form
Mai qu – from north China, made with wheat, fermented with Aspergillus spp., pressed into a brick-shaped form
Da qu – derived from Mai qu, made with barley, wheat, and peas, fermented with Mucor spp. and Rhizopus spp., pressed into a brick
Da qu with red core – fermented with Mucor spp. and Absidia spp. (dominant), Rhizopus spp. and Aspergillus spp. (less dominant), and Monascus spp. (minority), used especially in the production of Shanxi aged vinegar
Fu qu – a more recent type, made with wheat bran, fermented with pure cultures of Aspergillus oryzae

Regardless of the diversity of its forms, the solid-state cultivation of A. oryzae seems to be the key to inducing the production of hydrolytic enzymes, which are responsible for the breakdown of macromolecules in traditional fermented foods (Machida et al. 2008).

With soy sauces, most Japanese styles use roasted wheat and defatted soybean meal as a substrate for the koji, while most Chinese styles use the whole soybean for qu preparation. For more information about soy sauce production, check out our previous post on Yellow Pea Chiang Yu.

Some styles of koji production for spores (tane-koji or koji-kin) in Japan mix ash (tomo koji, lit. ‘friend of koji’) into the cooked rice, to create favourable conditions for the koji mould by increasing pH and providing certain minerals like potassium, magnesium, and phosphate, which help to increase spore production and resilience, as well as inhibiting various contaminants. The best ash is made from camellia, then zelkove (Zelkova serrata) and oak (Akita Konno).


Koji has been and continues to be referred to as a ‘malt’ by many Westerns, at least since the 19th century. This is understandable given its similar functional role in the production of grain-based wines to malt in the production of beer: that is, providing fermentable sugars. Koji and malt also share some general chemical similarities, as both saccharify starches into sugars with enzymes. The key difference, however, is that koji uses the enzymes produced by the metabolism of a living fungus, while the production of malt involves sprouting the grain and using the enzymes produced in the sprouting, after which point the enzymatic activity is halted through roasting. We have tried using fresh koji to make a mash for beer, with limited results; roasted koji has proven much more promising (more details in a later post).

At the lab, we have been growing koji on all sorts of substrates, including pearled barley, heritage barley varieties like nøgen byg, buckwheat, rye, quinoa and other Chenopodium spp., sunflower seeds, various beans, and more. Our mainstay has become pearled barley – it is what we make most often and what we know best.

photo credit: Chris Tonnesen

photo credit: Chris Tonnesen

A brief history of koji

300BCE – in Zhouli (‘Rites of the Zhou dynasty’), China – the first written mention of qu. The first conceptual framework to connect soy sauces, jiangs/misos, fermented black soybeans, grain-based wines like sake and li (a Chinese precursor to Japanese amazake), and other koji-based foods.

90BCE – in Shiji (‘Records of the Historian’), by Sima Qian, China – indications that fermented black soybeans and qu were already major commodities in the Chinese economy.

100CE – in Liji (‘Book of rites’), China – the earliest known description of how grain-based wines were made from millet and rice koji.

121CE – in Shuowen Jiezi (‘Analytical Dictionary of Characters’), China – earliest known written character for qu/koji, composed of a top radical for bamboo () over the character for chrysanthemum (). The etymology for this character interpreted by Huang (2000) stems from the idea that qu could have occurred when cooked rice was left in a bamboo basket exposed to air, which over time turned the yellow colour of chrysanthemum.
The contemporary character for koji/qu, in both Chinese and Japanese, is .

544CE – in Qimin Yaoshu (‘Important Arts for the People’s Welfare’), by Jian Sixie, China – the first known detailed description of how to make qu. It includes recipes for nine types of qu and 37 types of grain-based wine.

725CE – in Harima no Kuni Fudoki (‘Geography and Culture of Harima province’), Japan – the first known written mention of koji outside of China. Made using airborne koji moulds.

965CE – in Qing Yilu (‘Anecdotes, simple and exotic’), by Tao Ku, China – the earliest known reference to hong qu, or red rice qu. It includes a recipe for red pot-roast lamb, involving lamb simmered with red rice koji.

1603 – in Vocabulario da Lingoa de Iapam (‘Vocabulary of the Language of Japan’) – Japanese-Portuguese dictionary for Jesuit missionaries in Nagasaki. Contains entries for:
Côji [Koji], a yeast [sic] used in Japan to make sake, or mixed with other things.
Amazaqe [Amazake], a still-bubbling fermented liquid that has not yet completely become sake; or sweet sake.
This is the earliest known European-language document that references koji and amazake.

1712 – in Amoenitatum exoticarum politico-physico-medicarum (‘Exotic novelties, political, physical, medical’) by Engelbert Kaempfer – Kaempfer traveled and lived in Japan from September 1690 to November 1692, mentioning koji, or ‘koos’ as he called it, as part of the process of making miso.

1766 – Samuel Bowen, an American, begins producing, selling, and exporting Chinese-style soy sauce in Thunderbolt near Savannah, Georgia based on a technique he learned in China. Bowen was the first to introduce the soybean to North America (Hymowitz & Harlan 1983).

1779 – in Encyclopaedia Britannica, 2nd edition – the entry for ‘Dolichos’ mentions ‘koos’ (after Kaempfer).

1818 – in Account of a Voyage of Discovery to… the Great Loo-Choo Island [Ryukyu, or Okinawa], by Basil Hall – “…hard boiled eggs, cut into slices, the outside of the white being colored red.” This red colour was likely imparted to the outside of the shelled eggs by red rice koji, known in Japan as beni-koji.

1867 – in A Japanese and English Dictionary, by James C. Hepburn – the first written occurrence of koji referred to as a ‘malt’.

1878 March 10 – in Koji no setsu (‘Theory of Koji’), published in Japanese in Tokyo Iji Shinshi (Tokyo Medical Journal) by H. Ahlburg and Shinnosuke Matsubara – the first scientific article ascribing a latin binomial to koji mould. Ahlburg named the mould Eurotium oryzae, which was later renamed Aspergillus oryzae by Cohn in 1884. Japanese scientists rapidly adopting Western microbiology.

1878 Sept 12 – in Brewing in Japan, by R.W. Atkinson, British professor at University of Tokyo, published by Nature (London) – the earliest English-language document that mentions ‘tane’, or koji spores, and ‘tomo koji’, or wood ash.

1881 May 1 – R.W. Atkinson explicitly distinguishes koji from malt, and insists on the use of the Japanese word in English to avoid “erroneous impressions”.

1891 Feb 20 – The first article (appearing in the Chicago Daily Tribune) about Jokichi Takamine, a Japanese chemist residing in Chicago who developed method of using koji instead of malt to make whiskey, with 12-15% improvement in efficiency.

1894 Feb 23 – Takamine applies for a patent for ‘Taka-Diastase’, now known as the amylase produced by Aspergillus oryzae. This is the first US patent for a microbial enzyme.

1895 July – Takamine contracts with Parke, Davis & co. of Detroit, Michigan to manufacture and market Taka-Diastase on a large commercial scale. This is the earliest known commercially-produced enzyme in North America.

1897 – Yamamori Jozo-sho in San Jose, CA is the earliest-known company to produce shoyu (Japanese soy sauce) in the US.

1906 – Karuhorunia Miso Seizo-jo (California Miso Manufacturing Co.) in San Francisco is the earliest-known company to make miso in the US.

1908 – Kodama Miso Seizo-sho in Los Angeles is the earliest-known company to make and sell koji in the US, advertising its product as ‘Shiro Koji’.

1913 – Marusan Joto Shiromiso in Los Angeles is the earliest-known company to sell and advertise koji in English, as ‘Special Koji’.

1972 – The Erewhon Trading Co., Inc. catalog entitled ‘Traditional Foods’ advertises its koji imported from Japan. At this point there was a resurgent interest in koji in North America with the macrobiotic, natural-foods, and soyfoods movements.

2004 – Professor emeritus Eiji Ichishima of Tohoku University, Japan, proposes in Nippon Jozo Kyokai Zasshi (Journal of the Brewing Society, Japan) that Aspergillus oryzae become the ‘national fungus’ (kokkin), just like a national bird, flower, tree, or animal. The proposal is approved at the society’s annual meeting in 2006.

It should be noted that while the dominant popular narrative surrounding the flow of ideas – and associated structures of power – in the world has gone from ‘West’ to ‘East’, in the case of koji technology the knowledge has moved from East Asia to Europe and North America – very much the opposite.

For more information about the history of koji, look into the extensive book by Shurtleff and Aoyagi from 2012 called ‘The History of Koji’, available free online.


Evolutionary history and domestication

The evolutionary history of Aspergillus oryzae provides an interesting model for investigating mechanisms of domestication, and how they might differ in microbes compared to animals or plants.

The closest relative to A. oryzae is A. flavus, the two species sharing 99.5% genome-wide nucleotide similarity. Yet this difference is enough for the species to exhibit markedly different metabolic and behavioural characteristics. Though under certain conditions (mainly incubation longer than the standard three days for koji fermentation) some strains of A. oryzae have been shown to produce mycotoxins such as maltoryzine, ochratoxin A, and kojic, aspergillic, cyclopiazonic, and b-nitropropionic acids (USEPA 2012; Ciegler & Vesonder, 1987; Blumenthal 2004), the fungus has been used safely in food production for centuries, is Generally Regarded As Safe (GRAS) by the United States Food and Drug Administration (FDA), and has Qualified Presumption of Safety (QPS) by the European Food Safety Authority (EFSA). A. flavus, on the other hand, is an agricultural pest of several seed crops and producer of aflatoxin, another mycotoxin and one of the most potent naturally-occurring carcinogens.

In a 2012 study, Gibbons et al. compared the genome sequences of 14 geographically and industrially diverse strains of A. oryzae and A. flavus with their reference strains to learn more about the flavus-oryzae lineage and “the functional changes associated with microbe domestication and the impact of the process on genome variation.” Firstly, they found that the genome-wide nucleotide diversity among the A. oryzae strains was around 25% of that among the A. flavus strains. This result, paired with the knowledge that A. oryzae is monophyletic, indicates that all strains of A. oryzae originate from a single domestication event i.e. one common ancestor. Furthermore, two of the A. flavus isolates showed a closer affinity to A. oryzae than to the other A. flavus isolates, suggesting not only that A. oryzae descended from A. flavus but that it likely originated within an atoxigenic clade of A. flavus. Some strains of A. flavus are indeed known to be atoxigenic, so such an origin is evolutionarily plausible.

Some of the possible selective pressures for A. oryzae are illustrated by the relationship between koji and sake production. Aflatoxin is genotoxic to Saccharomyces cerevisiae, the principal yeast involved in the fermentation of sake and other grain-based wines, which means that evolution of the atoxigenic A. oryzae and/or its atoxigenic A. flavus ancestor could have been driven in part by its impact on yeast survival (Gibbons et al. 2012). In other words, that saccharification and alcoholic fermentation occur in parallel in many methods for sake production means that a less toxigenic saccharifying mould would allow for a stronger culture of alcoholically fermenting yeast, enhancing the production of sake and leading to alcohol levels up to 18-20% by volume – the highest recorded level of alcohol in a beverage without distillation (Murooka & Yamshita 2008). The fact that humans like alcohol probably directly selected for a non-toxic strain of saccharifying mould – leading to a technology with many applications beyond alcoholic fermentation itself.

Overall, what has emerged from this and other studies is a picture of microbe domestication different from that with many animals and plants: while domestication of many plant and animal species has been largely effected through “genetic tinkering” of developmental pathways affecting growth and morphology, the domestication of some microbes including A. oryzae was driven by the restructuring of metabolism (Gibbons et al. 2012).

IMG_0352 2.JPG

Making Koji

Now we can make some koji.
This recipe yields about 1450g of finished koji from 1 kg of dry pearled barley.

You will need:
1kg dry pearled barley, or another grain (it is worth noting that in sake production, the more polished/pearled the grain of rice, the more expensive the sake)
sufficient water for soaking
~40g koji-kin / tane-koji / koji spores
a thermomix, or strong blender, or mortar and pestle (less than ideal)
a steam oven, or something to steam in, or a slow cooker, or a pot of boiling water (as a last resort)
hand sanitiser
latex gloves
a gastrotray, or another similar tray
a clean cloth that can cover the tray
a koji chamber (we use an upright fridge turned off and fitted with heating mat and temperature probe connected to PID controller – essentially some place that can maintain a constant temperature of 30˚C and retain humidity, and has some space for airflow. For more information on creating a similar device, check out our previous post ‘Home Made’).

1. Soak pearled barley overnight.

2. The next morning, turn on koji chamber to 30˚C. 

3. Steam barley (100˚C) for 90 minutes in perforated gastro tray.

3. Remove barley from oven. While it cools, blitz koji-kin in thermomix to a fine powder (20g koji-kin / 1kg cooked barley).

4. Once barley has cooled to a comfortable temperature, sanitize hands with alcohol, put on latex gloves and break up chunks thoroughly. Pour or scoop barley into standard full-size gastros to a depth of about 2cm.

5. Prepare a warm, damp, wrung-out cloth to cover the koji.

6. When the barley has reached 35˚C, inoculate with powdered koji-kin and mix thoroughly to coat every grain. Smooth out barley and cover with the damp cloth.

7. Place the tray into the koji chamber (time T+0). Fill from the top racks down, to make use of the most heat. The barley should stay around 30˚C, and not go too far above. Place the temperature probe into the barley itself to keep track of the internal temperature – this is crucial to not letting it overheat. Put it in the koji chamber on the uppermost shelf, as it is in the warmest part of the chamber. Close door.

8. At T+6h, remove tray and turn the koji - mixing to aerate and ensure even distribution of spores. Redampen the cloth, cover and return to chamber. Nestle the probe into the koji on the top shelf. Close door.

9. At T+12h, turn koji again. It should start to smell fruity and fragrant. This time, create two furrows in the koji lengthwise with hands – the furrows should be as deep as possible without being able to see the pan through the grains. Return the koji to the chamber with a newly dampened cloth. Nestle the probe into the top shelf koji. This time, keep the chamber door open a crack to prevent overheating.

10. At T+18h, turn the koji a final time, again with furrows. Lightly re-dampen the cloth (at this point the chamber should be around 95% relative humidity) and return the koji to the chamber. Nestle the probe into the top shelf koji with the door slightly cracked.

11. Monitor the temperature carefully over the next 18h - it should stay between 25˚C and 30˚C in order to not denature any of the peptidases.

12. At T+36, the A. oryzae mycelia will have permeated the grains and they will hold together in a spongy white cake. 

13. If using koji for further fermentation, use while it is still white. If saving koji as koji-kin, let the A. oryzae continue to develop until it begins to sporulate and turn green. Once it turns green, break it up in the tray and let it dry slowly, somewhere warm and dry. Once completely dry, store and use for future koji inoculation.

14. Happy fermenting!

If the koji turns sticky and starts to smell ammoniated and like sour bananas, the A. oryzae has probably been killed due to an excessive temperature, and the substrate has been taken over by Bacillus subtilis – bacteria that are often found in certain alkali fermentations. It is the reason why natto is sticky and ammoniated. Discard, and next time be sure to keep the temperature in the center of the grains around 30˚c. It might take some experimenting to get it right depending on your incubation infrastructure.




Akita Konno Co., Ltd. “Outline of Koji and Yeast Stater [sic] producing process”. Japan. 17 Dec 2013. <>.

“Aspergillus oryzae”. Wikipedia. Sept 3 2013. Nov 24 2013. <>.

“Aspergillus oryzae Final Risk Assessment”. Biotechnology Program under the Toxic Substances Control Act (TSCA), United States Environmental Protection Agency. 27 Sept 2012. 23 Dec 2013. <>.

Chen, Fusheng et al. “Cereal Vinegars Made by Solid-State Fermentation in China”. . 2008.

Gibbons, John et al. “The Evolutionary Imprint of Domestication on Genome Variation and Function of the Filamentous Fungus Aspergillus oryzae”. Current Biology. 22: 1403-1409 (2012).

Glenn, Dianne and Rogers, Peter. “Industrialization of Indigenous Fermented Food Processes: Biotechnological Aspects”.

Hammes, Walter et al. “Microbial ecology of cereal fermentations”. Trends in Food Science & Technology. 16: 4-11 (2005).

Hui, Y. H. et al. Handbook of Food and Beverage Fermentation Technology. New York: Marcel Dekker Inc., 2004.

Machida, Masayuki et al. “Genome sequencing and analysis of Aspergillus oryzae”. Nature. 438: 1157-1161 (2005).

Machida, Masayuki et al. “Genomics of Aspergillus oryzae: Learning from the History of Koji Mold and Exploration of Its Future”. DNA Research. 15: 173-183 (2008).

Murooka, Yoshikatsu and Yamshita, Mitsuo. “Traditional healthful fermented products of Japan”. Journal of Industrial Microbial Biotechnology. 35: 791-798 (2008).

Nielsen, Dennis et al. “Mixed microbial Fermentations and methodologies for their investigation”. Unpublished.

Shurtleff, William and Aoyagi, Akiko. History of Koji – Grains and/or soybeans enrobed with a mold culture (300BCE to 2012). USA: Soyinfo Center, 2012. 17 July 2013. 17 Dec 2013. <>.

Tzean, SS et al. “Aspergillus oryzae var. effusus”. BCRC. Taiwan: Gifu University, 1990. Nov 24 2013. <>.

Move Over Wine

Added on by Avery McGuire.

by Avery McGuire

Over the last decade Nordic cuisine has been evolving rapidly. Many chefs have turned to the landscape for inspiration, rediscovering the diversity of wild and forgotten foods and using them to create distinct expressions of time and place. Yet while the food on the plate is a clear indication of the season and region, the drink in the glass often reflects distant terroirs and far-off cultures. Why is there this growing contrast between the cultural and geographical characteristics of food and drink, especially in the restaurant setting? We dove into the books and conducted interviews with sommeliers from around the Nordic region to try to answer this question.

Wet and dry

Due to differences in geographical climate, already in the 16th century there was a clear division between the food and beverage cultures of Northern and Southern Europe. Milk, meat, butter, and beer characterized the cold climate and forested landscape of the north, while the warmer south was known for its bread, olive oil, and wine (Montinari 2006). The foodways of these regions were built around the ingredients available, hence the strong geographic correlation with the consumption of different beverages. Yet this contrast in drinking habits is not based on climate and geography alone. Drinks are classified in terms of their social meanings; no alcoholic drink is ‘socially neutral’: every drink is loaded with symbolic meaning and every drink conveys a message about its consumer, the occasion, and the location (SIRC 1998). Cultural practices around both wine and beer, and their emergent associations with social status, have reinforced the contrast between wine and beer drinking cultures.



Mack P. Holt characterizes this cultural division into ‘wet’ and ‘dry’ drinking cultures. In Southern Europe where a ‘wet’ drinking culture persists, “drinking is a part of daily life and alcohol is consumed with meals on a regular basis as a form of sociability as well as a vital element to commensality.” (Holt 2006). Meanwhile, in the ‘dry’ drinking culture of Northern Europe, “drinking alcohol is perceived as something less connected with meal time and more associated with drinking in taverns, pubs, or beer halls.” (Holt 2006) In other words, the general and perhaps misguided understanding was that ‘wining’ was for ‘dining’, while ‘beering’ was for ‘cheering’. Despite the many different circumstances in which beer is celebrated and bears cultural and social significance in Scandinavia, the overwhelming association of beer with informal occasions has also diluted its perceived significance and value. We are not trying to suggest that beer was never important – it has carried great cultural significance for centuries; rather, it has not been specifically valued as part of restaurant culture in Scandinavia, especially in the last half-century, to the same extent as wine.

The status of beer is and has been at a disadvantage for decades, which perhaps stems from the drink’s complex history. Looking back to the medieval times weak and low-proof beer was consumed frequently by both children and adults, and for good reason. The purification of water that happens during the brewing process killed off numerous harmful bacteria therefore preventing many water-borne illnesses. Beer was the safe way to quench one’s thirst. Individual families, for their own consumption, brewed weaker beer, while stronger beers were brewed for festivals and celebratory occasions. It may have partly been this necessity to drink beer for hydration that limited the image of the Nordic beer-drinking culture. Yet beer has a much richer cultural heritage than this element of the past suggests; it has significant value in Scandinavian society, which can and should be restored. 

experimental hops tasting

experimental hops tasting

Roles of alcohol in society

In almost every society consuming alcohol is a social act; it does not take place ‘just anywhere’, and most cultures have designated environments for communal drinking. Subsequently one’s choice of beverage becomes a significant indicator of one’s status, serving as a declaration of membership to a particular group, generation, class, sub-culture, or nation (SIRC 1998).

In the wine-drinking cultures of the south, wine is seen on a sliding scale. There are the inexpensive table wines, cultural icons present on every table. While this wine is not necessarily highly regarded for its taste, it plays an important role in the cultural understanding of eating and drinking as a communal act. Many dining experiences, especially when dining out, deserve a wine of a higher caliber; these wines are often more complex, and crafted with precision and care. It is largely these highly appreciated wines that have lead to the perceived superiority of wine in general. The northern beer culture, however, has the potential to achieve this same gradation, from everyday beers to greatly appreciated craft brews appropriate for fine dining, and in fact, elements of this already exist.

As Blocker notes: “Beer – and especially branded beer – became a form of ‘conspicuous’ product consumption in which Danes identified themselves with particular brands that had symbolic and social significance” (Blocker et al. 2003). Certain beers have become associated with the working classes, while other “better, stronger and tastier” ones have gained reputations as first-class beers, associated with intellectuals and well-off members of Danish society. Simply put, “drinking the[se] products [came to be] interpreted as expressing identification with the ‘quality’ of Danish culture” (ibid.).

wild hops in Copenhagen

wild hops in Copenhagen

Value and access

Wine was (and still is) regarded as something complex, requiring study and therefore accessible to and understood by only a select few. Beer, on the other hand, is often regarded as cheap, filling, less profound, and more accessible. This perceived ease of access – both economic and aesthetic – may have reduced beer’s potential for high value, yet these preconceived ideas about beer are starting to change; many are rediscovering beer’s complexity, history, and value, and seek to share this knowledge.

Quality of ingredients, locality, and storytelling all contribute to the perceived prestige of any food product, including beer. It can be rich with history or have a unique story to tell, and can be made using high quality, local, or wild ingredients giving it a complex, unique flavour profile. These factors contribute to its uniqueness, which can be harnessed to generate gastronomic value.

In addition to these factors, value is often enhanced by scarcity, which is partly why wine and champagne are more valued than milk or water (aside from their complex craft). The aging process that some wines undergo is partly responsible for this – the product will often be consumed over the course of its aging, thus yielding a product of greater and greater scarcity. This increase in value with time can also be applied to beer: "certain beers, kept properly, will improve and deepen with age, becoming increasingly complex and even profound." (Oliver 2012) Unique beers served only in selected restaurants and specialty bars can gain a different type of value and appreciation from those served at every local pub and sports bar. The context of the product is an important part of its value.


This shift to valuing diversity and uniqueness in beer is already occurring both culturally and commercially. Microbreweries have been popping up across the globe and people are regaining an interest in exploring beer’s potential.

Today’s craft or gourmet beer market seems to be driven mainly by two different approaches to brewing. One approach is to intensify certain parts of the process, brewing bigger, bolder beers like triple IPAs and double stouts. The other approach is to focus on the history of a region, pulling the past into the present by working with rare, wild and/or native ingredients and traditional or forgotten techniques to give the beers unique characteristics. These elements are what give craft beers their edge, setting them apart from the beer one finds in most pubs and corner stores.


It is a well-known fact that the bottle and label have a great impact on how its contents are perceived and valued. Many of the higher-end beers currently on the market are sold in larger bottles, a clear strategy to signify quality. Perhaps more interesting though is the difference in attitude and sentiment conditioned by the bottle size. The size of a wine bottle lends itself to sharing, inviting a sense of commensality to its consumption. Most beer bottles, on the other hand, are designed for a single drinker, and this implicit individualism draws the focus away from a shared dining experience – even if everyone is drinking the same type of beer. A further significance of bottle size has to do with aging potential: the larger the bottle, the lower the contents' proportional exposure to oxygen, thus enabling a longer aging process. "As with age-worthy wines, beers that are destined to be beautiful after ten years or more of bottle age will tend to first experience a tough, inexpressive, and disjointed youth." (Oliver 2012) Some beers, such as Chimay, have traditionally been aged in Jeroboams; yet there seems to be much more documented knowledge on aging wine than beer. An interesting direction for aspiring breweries to take, then, would be to increase bottle size, both to gesture to this commensality and to open up experimentation with aging.


More drink

Nordic cuisine has come a long way in revalorizing what used to be considered the least valuable of ingredients: weeds, seconds, and plants formerly inedible. It accomplished this by focusing on the diversity of flavours and techniques available to unlock new or forgotten forms of deliciousness. This attitude broke down the perceived inferiority of Nordic food, and it has the ability to do the same with beverages. As one of our interviewees stated, “New Nordic cuisine (if you want to call it that) says we are free to do what we want, there are no rules and no strings attached, therefore we can do our own version of what we think a Scandinavian beverage paring should be.”

Move over wine – beer deserves a place at the table.


Askegaard, Søren. European Food Cultures: An Exploratory Analysis of Food Related Preferences and Behaviour in European Regions. Thesis. 1995. N.p.: C ENTRE FOR MARKET SURVEILLANCE , RESEARCH AND STRATEGY FOR THE FOOD SECTOR, n.d. Print.

Berrong, Nathan. "Berrong on Beer – Why Do Restaurants Neglect Beer? – Eatocracy - Blogs." Eatocracy RSS. CNN, 3 Apr. 2012. Web. 13 Sept. 2013.

Blocker, Jack S., David M. Fahey, and Ian R. Tyrrell. Alcohol and Temperance in Modern History: An International Encyclopedia. Santa Barbara, CA: ABC-CLIO, 2003. Print.

Fjellström, Christina. "Mealtime and Meal Patterns from a Cultural Perspective." Scandinavian Journal of Nutrition 48.4 (2004): 161-64. Print.

Holt, Mack P. Alochol: A Social and Cultural History. N.p.: Bloomsbury Academic, 2006. Print.

Montanari, Massimo. Food Is Culture. New York: Columbia UP, 2006. Print.

Oliver, Garrett. The Oxford Companion to Beer. Oxford University Press, 2012. Print.

Social and Cultural Aspects of Drinking. Publication. Oxford: Social Issues Research Centre, 1889. Print.

"Why Isn't Beer Gourmet? | The Sauced Chef." The Sauced Chef RSS. N.p., 14 Sept. 2009. Web. 13 Sept. 2013.

Wood for food: a primer on pyrolysis

Added on by Guillemette Barthouil.

by Guillemette Barthouil


Smoking is valued nowadays not only for preserving food, but also as a distinct set of flavours that can reflect the landscape of the region. Pyrolysis, the thermochemical decomposition of organic matter, breaks apart the three main components of wood: cellulose, hemicellulose and lignin. Each influences the colour, flavour, preservation and surface texture of the food – this information is summarized in Figure 4 below. Controlling pyrolysis is the key know-how involved in good smoking. Overall, for best results the wood moisture should be lower then 25% and its combustion temperature around 400°C.

“Smoking is one of the oldest food preservation methods, probably having arisen shortly after the development of cooking with fire.” (Encyclopedia Brittanica)

Most articles I have read for this research have started with the same statement. Humanity has used this technique for so long, it seems rather strange to try to explain it – but that is our job. All chefs know one has to understand a product or technique in order to make the most out of it. We use some scientific knowledge to enhance the desired, latent characteristics of a product, with the goal of better understanding how traditional knowledge could have been cultivated in a geographic area. And smoking is a great example.

The food history of the Nordic countries is particularly characterised by a ‘storage economy’ – a concept applicable to most parts of the world with seasons, here emphasised by the extreme climate. Most processes that we study -– drying, salting, smoking, fermenting, and others – were indispensable in these conditions. By increasing heat and lowering humidity, smoking enabled food to dry up more quickly, preserving it for long periods of time.


In the past decades, the taste for salted, dried and fermented food has shifted toward fresher food, gravlax being a good example. The taste for smoked products, however, has remained. Smoking is now not only important for preserving food, it is a valued flavor that can reflect the landscape of the region. Smoking in time and place depends on many things: the seasonal fish available, the smoking technique and temperature used – for cold smoking, the temperature drops the further north you go – and most importantly, the type of wood. Trees are part of the landscape before they become an essential component of the product’s taste. Alder trees growing in humid areas have been used along the west coastline of Norway and on the island of Bornholm in the Baltic; birch is a typical flavor from mountainous zones; dried manure is still used in the windy and harsh Icelandic land since trees and shrubs are in short supply; this list could go on. Understanding these traditions allows us to think of other flavors that could emerge from a specific land as we come to know it. Gaining a deeper understanding of wood pyrolysis and the science of smoke will also help us in our choices.


Smoke is not a simple gas. It is a mixture of three state of matter: an aerosol of solid particles, liquid drops and vaporized chemicals. These vaporized chemicals only count for 10% of the volume but do more then 90% of the job. And as you might have guessed, the composition of the smoke depends on the nature of the burning fuel and the conditions of combustion.

Pyrolysis is a thermochemical decomposition of organic matter brought about by high temperatures. To produce quality smoke the wood should undergo an incomplete combustion of organic materials in the presence of limited oxygen and medium temperature.

Wood consists of three primary materials. The wood’s cell wall is composed of micro-fibrils of cellulose (40 to 50%) and hemicellulose (15 to 25%) impregnated with lignin (15 to 30%).

Figure 1 – Wood composition

Figure 1 – Wood composition


Cellulose is a carbohydrate polymer - a linear chain of D-glucose (between 15 to 15000) which forms the framework and the substance of all plant cell walls.


Figure 2 – Cellulose

Figure 2 – Cellulose

Hemicellulose is a matrix of polysaccharides present along cellulose is almost all plant walls. It differs from cellulose in that hemicellulose is a shorter chain branched polymer with low molecular weight. While cellulose is composed only of glucose, hemicellulose can include other sugars like xylose, mannose (both found predominantly in hardwood trees), galactose (in softwood trees), rhamnose and arabinose. Though both aggregates of different sugars, cellulose and hemicellulose break down into similar molecules during the incomplete combustion.


Figure 3 – Hemicellulose

Figure 3 – Hemicellulose

Lignin provides compressional strength to the cell wall, unlike the flexible strength conferred by cellulose. Without lignin, terrestrial plants probably could not have reached the sizes they do today, as cellulose by itself does not provide enough resistance to gravity. It is made of intricately interlocked phenolic molecules – essentially rings of carbon atoms with various additional chemical group attached – and its one of the most complex known natural substances. The higher the lignin content of wood, the harder it is and the hotter it burns: its combustion releases 50% more heat than cellulose.


The sugar in cellulose and hemicellulose breaks apart into many of the same molecules found in caramel. They are carbonyl molecules that react with amino acids and sugars to create a Maillard-type reaction that generates new flavours and yellow to dark brown color. During pyrolysis, sweet maltitols, bread-like aroma from furans, nutty lactones, and other volatile molecules are produced. All together they soften the heavy phenolic compounds.

The interlocked phenolic rings of lignin break apart from each other into smaller, volatile phenols and other molecules which most often have specific aromas. The most distinctive ones are isoeugenols, one of the main flavour component of clove, creosols that bring peat notes, vanillin that smells as it sounds, guaiacols contributing to the general spiciness.

The smoke has many other effects due to many different chemicals broken apart during the pyrolysis. The following table tries to summarise them.

Figure 4 – Effects and mechanisms of pyrolysis

Figure 4 – Effects and mechanisms of pyrolysis

As you might have noticed in the ‘notes’ column, capturing the desired smoking effects depends mainly on the wood humidity and the smouldering temperature. Controlling the pyrolysis is the key know-how of a good smoker. Freshly-cut wood contains 40-60% moisture which is not suitable for smoking. A good wood containing less than 25% moisture is preferred. Professionals agree that the combustion temperature is best around 400°C. Higher than this, the flavour molecules are broken down into simpler, harsh, or flavourless molecules. Lower pyrolysis – under 200°C – degrades cellulose and hemicellulose into acetic, formic and other acids. These acids play an important preservative role but they also make the food taste acrid at high levels. High lignin woods require special attention since they burn too hot unless their combustion is slowed by restricted airflow or higher moisture.


Figure 5 – Smouldering temperatures

Figure 5 – Smouldering temperatures

Controlling the smouldering temperature is not only important for flavours, it influences the PAH concentration. Polycyclic Aromatic Hydrocarbons (PAHs) are formed in incomplete combustion processes, which occur whenever wood, coal or oil are burnt. Particular attention has been paid to the highly carcinogenic benzo[a]pyrene (BaP). A number of studies on smoked foods reveals that the highest levels of PAHs are found in products from traditional kilns that use smouldering wood or sawdust. In such kilns the combustion temperature is difficult to control and is usually very high. Toth and Blaas (1972) found that there is a linear rise in the concentrations of BaP and other PAHs in the smoke phase between smoke production temperatures of 400 - 1000 °C. These traditional techniques are often considered synonymous with ‘quality’ and ‘authenticity’.... so what should we do then? Eat industrially-smoked products because they are ‘more healthy’? My personal choice will always go toward taste but this does not mean we cannot adapt traditions to make the best of both kinds of knowledge. It has for example been proven that both cold-smoked and hot-smoked fish by an external smoke generator had lower PAH content. Moreover a Danish study reported that a cold-smoked fish has a lower BaP concentration then hot-smoked ones. In order to diminish the contamination of smoked products by PAH, the clear recommendation is to use indirect smoking, preferably cold smoke, and to maintain your smouldering temperature around 400°C.

These conclusions stimulated me to experiment a little.

Hot-smoked fishes are nowadays more popular in Scandinavia then cold-smoked ones, mackerel being the most consumed. How could we achieve this same taste without hot-smoking the fish and keeping the PAH low? Hot-smoking occurs within the range of 52°C to 80°C.  At this temperature food cooks while smoking. I therefore decided to cook the fish first in our combi oven and then cold-smoke it.


After a few experiments trying to find the best cooking temperature and humidity, here is the recipe:


Cold-smoked mackerel

For very fresh mackerel of around 400 g.

Gut them and brine them 8 h at 4°C in a solution of 20% salt of the total.

The aim is to reach a salt content of 3% in the fish … like the salinity of seawater in the Atlantic ocean...

Remove fish from the brine and place on a perforated tray. 

Cook them in the oven at 70°C with 60% humidity.

Program your combi oven so when the core temperature reach 59°C the oven stops.

Take them out of the oven and cool them down in the blast freezer until they reach 4°C.

Cold smoke them for about 24h. We used beech wood but many other options are possible.

One of the great thing about this technique is that you can accurately control cooking temperature and humidity, things that are difficult with a hot-smoker. This control ensures the smoke flavours stay light and delicate, a taste certainly more suited to a contemporary palate.




Duedahl-Olesen, L.; White, S.; Binderup, M.L. Polycyclic Aromatic Hydrocarbons (PAH) in Danish Smoked Fish and Meat Products, Polycyclic Aromatic Compounds, Vol. 26, 3, 2006, p. 163-184

Knockeart, C., (1990), Le fumage du poisson, IFREMER

Mc Gee, H. (2004), Food & Cooking: an encyclopedia of kitchen science, history and culture, Hodder and Stoughton.

Myhrvold, N. and al. (2011), The modernist cuisine: the art and science of cooking, The cooking Lab, Vol 2, p 134 - 149.

Siesby Birgit, (1997), Scandinavian ways with fish, Fish: Food from Waters, Oxford Symposium, p 280 - 282

Toth, L., Blaas, W., (1972). The effect of smoking technology on the content of carcinogenic hydrocarbons in smoked meat products. Fleischwirtschaft, 52, 1419-1422.


Bog butter: a gastronomic perspective

Added on by Ben Reade.
The house of the Butter Vikings Patrik and Zandra

The house of the Butter Vikings Patrik and Zandra

by Ben Reade.

This paper was first published in 'Wrapped and Stuffed: Proceedings of the Oxford Symposium on Food and Cookery 2012'. The complete Proceedings is available from Prospect Books; a video recording of the presentation of this paper can be found here (starting at 33 minutes), and a podcast about it here.





 People dig for peat. Once dry, this peat burns hot and lets off an evocative smoke that brings to mind the cooking and heating methods of yesteryear. The peat-cutters harvest their quarry from dark brown, water-logged quagmires. Occasionally, these accidental archeologists discover artifacts left by people long gone. One such artifact, among the most commonly unearthed items from the watery, misty bogs of Ireland and Scotland, is known as ‘bog butter’. Due to the frequency of these findings and its mysterious nature, it has been fairly well studied from an archaeological perspective, perhaps the most thorough investigation being that by Caroline Earwood (1). In this study I will attempt an exploration of the substance through the eye of a chef and gastronome, combining available literary evidence with our own practical research. We made our own bog butter and subsequent gastronomic analysis with the hope that a new gastronomic perspective on the topic would give us access to a more pragmatic understanding of how and why ancient peoples buried their butter.

Bog butter is butter that has been buried in a peat bog (2). It has occasionally been confused with animal adipose tissue (most commonly sheep tallow), which has been preserved in the same manner. Over 430 instances of bog butter have been recorded (3). Of these, 274 have been found in Scotland and Ireland since 1817. These samples are well catalogued by Caroline Earwood. The earliest discoveries are thought to come from the Middle Iron Age (400-350 BC), though this does not exclude the possibility of much more ancient roots. More recently one firsthand account tells of butter being buried for preservation in Co. Donegal 1850-60 (4). In 1892, Rev. James O’Laverty, an advocate of the argument that the butter was buried for gastronomic reasons, dug some butter into a ‘bog bank’ and left it for eight months. His experiment was carried out in much the same spirit as ours – for analytical purposes and not for a cultural or preserving motive (5).

This paper aims, by making bog butter using appropriately basic technology, to explore why the boutyrophagoi, or ‘butter-eaters’, across Scotland, Ireland, the Faeroe Islands, Finland and Norway, as well as Kashmir, Assam and Morocco have buried their butter, with special focus on the Irish, Scottish and Scandinavian traditions (6). The aim of this paper also extends to a discussion of whether or not butter preserved by this method can have a hedonic value for today’s palates, and possibly some use in contemporary cuisine.

Peat bogs are, by their nature, cold, wet places; almost no oxygen circulates in the millennia-old build-up of plant material, which creates highly acidic conditions (our site had a pH of 3.5). Sphagnum moss bogs have remarkable preservation properties, the mechanisms of which are poorly understood (7). Early food preservation methods have been researched extensively by Daniel C. Fisher, in relation to the preservation of meat. In an attempt to recreate techniques used by paleoamericans in North America, Fisher sunk various meats into a frozen pond and a peat bog. A key finding from his research is that after one year, bacterial counts on the submerged meats were comparable to control samples which had been left in a freezer for the same amount of time (8). In fact, suitable foods can probably be aged in many types of soil: salt-rich that will provide dehydration, very cold/freezing that will freeze foods or slow degradation, or, as in our case, anaerobic and acidic conditions to prevent microbial action and oxidation. To our canny ancestors, this preserving characteristic provided an ideal place to bury foods (9).

Around two thirds of the bog butter that has been discovered has come in a container or wrapping of some description. These containers are varied; during the spring and summer months when butter was abundant, dairymaids probably used almost anything they could for storage. The most common containers are wooden. These can be described under the broad classifications of kegs, churns, bowls, dishes, boxes, troughs, methers, firkins and piggins (10). The slowly evolving techniques of the artisan can be seen in these containers and until recently, dates were ascribed to archeological examples of bog butter in part on account of the workmanship of the container. Willow baskets, staved tubs, or bark wrappings have been used, as have bladders, intestines, and skins or woolen cloth (11).

Buried foods around the world

banana bread (Ethiopia, banana dough),

buried eggs (China, eggs), 

davuke (Fiji, bread fruit); 

formaggio di Fossa (Italy, cheese); 

ghee (India, clarified butter); 

gravadlax (Scandinavia, salmon); 

gubenkraut (Austria, cabbage); 

hákarl (Greenland, Greenland shark); 

igunaq (Inuit Arctic, walrus); 

kiviak (Greenland, auks in a seal skin): 

lutefisk (Scandinavia, white fish); 

muktuk (Alaska, seal flipper);

reindeer’s stomach (Sápmi, Sweden, stomach with contents);

rue tallow (Faroe Islands & Iceland, sheep’s tallow);

sealskin poke (Alaska, meat/dried fish with seal fat); 

smen (Morocco, clarified butter);

surmjølk/myrmjølk (Norway, milk);

Many fermented foods are prepared in fully or partially buried amphoras, including wine in Armenia and soya sauce in Korea.


Sometimes a combination of materials has been used, such as bark with a bladder, or with a willow basket. One example used a barrel bound in a deerskin to stow the butter into its peaty hiding place (12). One particularly interesting find, discovered in Rosmoylan (Co. Roscommon, Ireland) dates from the late Iron Age. Within a two piece barrel, the butter was surrounded with plant fibers from sedge (Eriophphorum vaginatum), bent grass (Agrostis sp.) and the soft-textured moss, hypnum (Hypnum cupressiforme) (13). All three of these plants have a long history of being used by people in mattresses and bedding; the latter takes its name from the Greek ‘hypnos’ meaning ‘sleep’. It is rather poetic that dairymaids had thought of these plants as appropriate for protecting their butter. The butter was wrapped up and made comfortable before being laid down for a long sleep in the bog.

Butter and other dairy products were frequently used as a form of taxation and rent (14). At Naas Castle in Sweden where we conducted our experiment, butter was a form of tax from the construction of the castle in 1500 until the end of the nineteenth century. One early fifteenth-century manuscript from Scotland, by the Rev. Dr. Archibald Clerk, reports sixteen horse-loads of butter and cheese being found hidden or ‘laid-up’ near a tenant’s house (15). Butter is valuable: for that reason alone worth hiding, even more so in lawless times. One author gives testimony that treasures were buried inside fats, so when bog butter was discovered it was pierced from all directions to check for valuables (16).

Butter had many uses. It could be used for waterproofing fabric and also a dwelling – one bog house has been discovered where butter and sand have been mixed together to make watertight cement (17). It might also have been used as a light source. Angus Grant’s 1904 report tells that the found butter was converted into candles but as ‘the candles spluttered and crackled, sending sparks of boiling tallow all round…they were voted uncanny, and promptly got rid of’ (18). So while there are many suggestions as to why butter was buried, I propose it was buried not only for its obvious value as a commodity but also for some gastronomic purpose.

While being buried during times of plenty to keep for leaner times, the butter may also have increased its gastronomic value during its time underground. The fact that bog butter never contains salt suggests that it may have been buried to preserve it in times when salt was scarce (19). During the warmer summers, when rancidity would quickly take hold, burying may have not only been a convenient way of preserving butter but also of creating a luxury food (20). As the Danish priest and topographer L.J. Debes said of the Faroese hoards of buried tallow, ‘the longer it is kept being so much the better’ (21). O’Laverty wrote that the Irish buried their butter to ‘sweeten it’ (22). He also suggests that it was put into peat to mature it and render it more nutritive (23). This increased nutrition may be some kind of representation in popular memory of how stored butter could provide for lean times, though it may also refer to a palatable flavour or some biochemical change within the butter itself which renders it more nutritive. Testimonies of bog butter tasting tend not to describe it as rancid, but many liken the altered fat to cheese. I had to make some to see for myself.

Patrik and Zandra. warlords.

Patrik and Zandra. warlords.

The Experiment

From: The Irish Hiudibras  (24)

But let his faith be good or bad,

In his house great plenty had,

Of burnt oat-bread, and butter found,

With Garlick mixt, in boggy ground,

So strong, a dog, with help of wind,

By scenting out, with ease might find:

And this they call the bravest meat,

That hungry mortals e’er did eat.

So it happened I was introduced to Patrick Johansen, an artisanal butter producer from Sweden. When I heard of his interest in aged butters and experimental butter with wild bacteria, we got to talking. Soon afterward we set to work creating some bog butter of our own. Patrick lives surrounded by great swaths of Swedish forest where elegant birches and enormous oaks grow, interrupted only by the occasional lake and, conveniently, peat bog. His house is a long way from anyone or anything; the water supply is a well in the garden and the only light from paraffin lamps. Patrick learned to make world-class butter from his grandmother, who in turn had learned from the matriarchal line before her. My approach dictated that he decide how everything should be done with the only limitation being that no technology should be used that was not available before the industrial revolution.



On the snow-sprinkled morning of 8 April 2012 we embarked on making our twenty-first-century bog butter. We decided that birch bark was to be our material of choice for crafting containers in which to bury the butter. Using an old iron axe we brought down a smooth, tall, straight birch, the bark from which we swiftly peeled. Birch bark unwraps from the trunk with remarkable ease at this time of year; it is soft and pliable yet firm and strong. We peeled the bark and sliced sections out of slightly smaller parts of the tree to make tops and bottoms to our ‘barrels’.

The birch is 'unwrapped' 

The birch is 'unwrapped' 

We had decided we should make some smaller samples which could be dug up sooner, and then a larger one which will sit underground for some years. The Irish Hudibras (1689) asserts that in Ireland, ‘butter to eat with their hog, was seven years buried in a bog’ (25). Seven years seems an appropriate length of time for our butter to age.

Although the technology of butter making has changed through the years, the principles remain roughly the same. Butter is made by souring cream, which is then churned until it splits into its fat (butter) and aqueous (butter-milk) phases. The solid butter is removed from the liquid buttermilk, clumped together and washed by kneading it in clean cold water – this removes excess milk solids and buttermilk, thereby increasing the butter’s longevity. After washing until the water runs clear, the butter is thrown. This is a process of subjecting the butter to some high impact (literally throwing it against the table), which expels excess water. Now you have butter. The whole process with the latest technology takes about fifteen seconds – for us, it took a little longer.

cream is filtered trough a grass 'nest'

cream is filtered trough a grass 'nest'

In earlier times, after milk had been left to stand to allow the cream to rise, it would need to be filtered to remove insects and dirt. Patrick tells me this was often done through grass which, as well as filtering, also supplied the cream with ample lactic acid bacteria. The cow’s teat, dairymaid’s hands, wooden containers and tools would have also provided plentiful souring bacteria. Filtering could also have been done with a piece of cloth, the advantage being that at the end of the diary season the cloth could be dried out, preserving spore forming lactic acid bacteria to be rehydrated and used to inoculate the new batches the following dairy season (non-spore forming bacteria would be lost). For our experiment, in the absence of a cloth from the previous season, we chose to use a ‘nest’ of grass for filtering. Then the cream was left to sour in a small stone-walled hovel, sunken into the hillside; the kind of dwelling that early pastoralists might have used while in summer pastures.

the souring 'hovel' 

the souring 'hovel' 

After souring, the cream must be churned. Traditionally this might have been done by filling a calf’s skin with the soured cream and hanging it from a wooden tripod or tree. The skin could then be swung back and forth until the cream split. Many bog butter samples contain large quantities of cow hair, suggesting that perhaps this method of swinging and shaking in a cow skin was often used (26). To avoid problems of cow hair and in the absence of a calf’s skin, we churned our cream by shaking it in a large jar.

Fresh water drawn from the well.

Fresh water drawn from the well.

The butter was then washed to remove the majority of butter milk. We did this with fresh cold water from the well in the garden – this is quite a simple process of allowing water-soluble parts to be washed out of the butter. Then we removed a large amount of the water by repeatedly picking up the lump of churned and washed butter and throwing it down onto the table. Throwing is an important step in the production of butter to be preserved, so we made sure to do it thoroughly.

Butter is swaddled in hypnum moss before being put to rest underground

Butter is swaddled in hypnum moss before being put to rest underground

We had made four small containers from birch bark and one from pine bark, and we also adapted a large old willow basket to hold a larger sample. In echo of the Rosmoylan bog butter discovery mentioned above we wrapped the butter in hypnum moss, before stuffing these moss-swaddled cylinders into our birch bark barrels – a comfortable bed in which our butter could sleep. Our willow basket held a half-firkin (approx. 12.5 kg) of butter, which was wrapped in a linen apron before being placed in the basket. It was important, as with historical bog butter finds, that the upper surface of the butter be entirely convex, in order that no water collect and stagnate on the top.

Downey et al. note that a large percentage of bog butter discoveries have been made along historic boundary lines (27). In 1892, James O’Laverty wrote that the butter was dug into ‘bog-banks’, perhaps another type of territorial confine (28). Debes’s 1673 description of the Faroe Islands describes how the preserved tallow or ‘rue tallow’ was buried in a ‘dike’ which certainly hints at a wall or embankment of some kind (29). There are many reasons why this should be the case, though it has largely been attributed to ritualistic motivations. I would suggest it may also have been to leave the food in a spot where people were unlikely to dig, and where there was a clear landmark. After looking for an appropriate bog to dig in we found a spot in a sphagnum and birch tree bog. The ground was soft enough to dig easily, and the holes slowly filled up with acidic bog water. We divided our containers between two holes and buried them at around 100cm below the surface. One of these stashes was unearthed and tasted three months after its burial (some notes on these tastings are found below). The second hoard will be allowed to age for a longer time, for seven years in echo of The Irish Hudibras, or perhaps left forever as some confusing archeology for the future: ‘It may, therefore, be termed a hidden treasure, which rust doth not consume, nor thieves steel away’, as Debes wrote in 1673 (30).


Finally, after counting our steps back to the path, we took a corner off a large rock with the back of our axe. This palm-of-your-hand-sized chunk of rock will now serve as a key. For whoever returns to dig up the butter, the stone key will fit into the rock and the butter will rise up from the bog.

The Results

At this point in time, five of our buried containers have been unearthed and tasted, and one remains in its peaty wallow. Tastings of three-month-aged bog butter have been made at both Nordic Food Lab in Copenhagen, Denmark and at the Oxford Symposium on Food and Cookery 2012 in Oxford, England. Various conclusions can be drawn from these tastings.

In its time underground the butter did not go rancid, as one would expect butter of the same quality to do in a fridge over the same time. The organoleptic qualities of this product were too many surprising, causing disgust in some and enjoyment in others. The fat absorbs a considerable amount of flavor from its surroundings, gaining flavor notes which were described primarily as ‘animal’ or ‘gamey’, ‘moss’, ‘funky’, ‘pungent’, and ‘salami’. These characteristics are certainly far-flung from the creamy acidity of a freshly made cultured butter, but have been found useful in the kitchen especially with strong and pungent dishes, in a similar manner to aged ghee.

As I worked with Patrick to make this bog-butter I noticed that all he ate all day was the butter itself. This, he said, is common among butter makers. A walnut sized lump will keep one sustained all day. If we consider ancient dairy based economies, many people may have gone all day eating only butter quite frequently. Occasionally it would be consumed on an oatcake, or with a piece of meat or fish, but often on its own. In times where transhumance brought people to relatively isolated and exposed locations, time spent inside with a fire to keep warm, along with infrequent washing and living space shared with their animals, may well have meant that stronger foods became more desirable, as they had some character that stood out from the already ripe surroundings.

Taste is to a large extent culturally defined, and modern tastes have been shaped by myriad modern factors that cannot be removed from the equation. When we taste this altered butter a the 2012 Oxford Symposium on Food and Cookery, we had to use some imagination. As O’Laverty wrote of his own bog butter experiment in the late nineteenth century, ‘for my own taste I would prefer butter cured in the modern way, but I have no doubt that usage would confer an acquired taste’ (31).

Proud boutyrophagoi

Proud boutyrophagoi

[update by Josh 29.10.13] – This past weekend, Guillemette and I took a trip up to Floda to visit Patrik and Zandra and make some butter together. We also used it as an opportunity to check up with the bog butter. The rainy Saturday afternoon saw us following the same path through the woods, finding the rock with the missing corner, and descending off the road down into the bog. Once we located the clearing with the buried treasure, we dug up the main deposit for a taste. It is still mossy, green, and earthy – maybe it was the fact that we were also wet, a little smelly, and surrounded by the moss like the thing itself, but the butter, eaten with muddy hands in the clearing in the bog, tasted really good.

The butter is now 1 year, 6 months, 3 weeks old, and counting.



1 Caroline Earwood, ‘Bog Butter: A Two Thousand Year History’, The Journal of Irish Archaeology, 8 (1997), 25-42.

2 Robert Berstan et al., ‘Characterization of Bog Butter Using a Combination of Molecular and Isotropic Techniques’, Analyst, 129 (2004), 3-8.

3 L. Downey et al., ‘Bog Butter: Dating Profile and Location’, Archaeology Ireland, 75 (2006), 32-34.

4 Earwood.

5 James O’Laverty, ‘The True Reason Why the Irish Buried Their Butter in Bog Banks’, Journal of the Royal Society of Antiquities of Ireland, 2 (1892), 356-337.

6 Berstan; David MacRitchie, ‘Wooden Dish Found Lately in the Hebrides’, Archaeological Notes, Reliquary, N.S II (1896); E. Estyn Evans, ‘Bog Butter: Another Explanation’, Ulster Journal of Archaeology 3rd. ser, 10 (1947), 59-62; PRIA, vi (1858), 369-72; personal email exchange with Anders Strinnholm of Stavanger Museum of Archaeology regarding collection item S9457 – three lumps of big butter from the Stavanger area of Norway; James Williams, ‘A Sample of Bog Butter from Lachar Moss, Dunfriesshire’, Transactions of the Dumfriesshire and Galloway Natural History and Antiquities Society, 3rd ser., 43 (1966), O’Laverty, ‘True Reason’. In Norway a similar practice of burying milk in peat bogs still exists as can be seen here: In Morocco butter is still preserved for long periods of time, sometimes underground, where it is known as smen.

7 ‘Terence J. Painter’, Carbohydrate Research, 338 (21 November 2003): 2777-2778.

8 Sally Pobojewski, ‘Underwater Storage Techniques Preserved Meat for Early Hunters’, The University Record, May 8 1995; retrieved 1/11/2012 from

9 Traditional foods for which burying is a part of the preparation/preservation process, or for which there is evidence that this may have been the case, include: banana bread (Ethiopia, banana dough), buried eggs (China, eggs); davuke (Fiji, bread fruit); formaggio di Fossa (Italy, cheese); ghee (India, clarified butter); gravadlax (Scandinavia, salmon); gubenkraut (Austria, cabbage); hákarl (Greenland, Greenland shark); igunaq (Inuit Arctic, walrus); kiviak (Greenland, auks in a seal skin): lutefisk (Scandinavia, white fish); muktuk (Alaska, seal flipper); reindeer’s stomach (Sápmi, Sweden, stomach with contents); rue tallow (Faroe Islands & Iceland, sheep’s tallow); sealskin poke (Alaska, meat/dried fish with seal fat); smen (Morocco, clarified butter); and surmjølk/myrmjølk (Norway, milk); Many fermented foods are prepared in fully or partially buried amphoras, including wine in Armenia and soya sauce in Korea.

10 Earwood; F. J. Hunter, ‘Iron Age Hoarding in Scotland and Northern England’, Reconstructing Iron Age Societies, eds. A. Gwilt and C. Hasselgrove, Oxbow Monographs in Archaeology, Oxford: Oxbow, 1997, 71.

11 James O’Laverty, ‘Bog-butter’, Ulster Journal of Archaeology, 1st ser., 7 (1859), 288-294.

12 Williams; Earwood.

13 Earwood.

14 O’Laverty, ‘Bog-butter’; personal communications between Professor E.C Synnott, Process Engineering Department, University College Cork, Ireland and Dr Alison Sheridon FSA Scot FSA AIFA, Head of Early Prehistory, National Museums Scotland.

15 Rev. Dr. Archibald Clerk, ‘Notes on Everything’, accessed via Dr. Alison Sheridon FSA Scot FSA AIFA, National Museum of Scotland.

16 Angus Grant, PSAS, 39 (1904-5), 246-247.

17 Niall Ó Dubhthaigh, ‘Summer Pasture in Donegal’, Folk Life, 22 (1984), 42-54.

18 Grant.

19 Earwood; Hunter; O’Laverty, ‘True Reason’.

20 Ó Dubhthaigh.

21 James Ritchie, ‘A Keg of Bog-butter from Skye’, Proceedings of the Society of Antiquaries of Scotland 75 (1941), 5-22.

22 O’Laverty, ‘Bog-butter’.

23 O’Laverty, ‘Bog-butter’; O’Laverty, ‘Ture Reason’

24 Some doubts exist over the author(s) of The Irish Hudibras. O’Laverty attributes it to William Moffet in 1855 (‘True Reason’). James Farewell (1689) is written in the copy held by the British Library. attributes the text to ‘Multiple Contributors’.

25 O’Laverty, ‘True Reason’.

26 O’Laverty, ‘Bog-butter’; Ritchie.

27 Downey.

28 O’Laverty, ‘True Reason’.

29 PRIA, 6 (1858), 369-72.

30 PRIA, 6 (1858), 369-72.

31 O’Laverty, ‘True Reason’.

Waxed Plums

Added on by Guillemette Barthouil.

trials by Sarah; post by Guillo, Avery, and Josh

Is it possible that waxing fruits, a symbol of our large-scale food distribution system that values appearance and practicality over taste, could be used instead for deliciousness?

In fact, many fruits when ripe produce a natural wax coating on their surface to reduce the water permeability of the skin. Pick an apple from a tree, rub it on your shirt and it shines; the natural waxes on the apple’s surface are polished. In addition to the wax, the surface of these fruits often host different wild yeasts and other small ‘debris’. Large- scale producers, in order to get rid of these yeasts and others microorganisms which can decrease a fruit’s shelf life, wash their fruits then recoat them with approximately the same amount of edible wax.

But here at the Lab we love wild yeast and bacteria.

At the end of September the plum season was nearing an end in Denmark. We received a box of pristine plums one day from our plum lady in Sweden. The fruits were perfectly ripe – golden, blushed with red, and, we assumed, covered with natural wax and yeast.


Beeswax is something we have been obsessed with for the last year or so. We started using it to coat our venison legs to keep them from losing moisture while the long fermentation continued. We made an ice cream with it for the dessert on our menu for Pestival. Sometimes we keep some around just to smell. Not only do we love it for its wonderful aroma and ability to infuse the food with a rich honey-like fragrance, but it also has the ability to seal a product from the outside elements. The protective barrier allows the product to retain moisture and creates the conditions for anaerobic fermentation. With preservation on our minds as winter nears, we thought beeswax could serve this purpose with our plums, enhancing the function of the natural wax to keep them even longer. The unwashed and unblemished plums were dipped into beeswax, sealed with their own microorganisms, and left to ferment.


Plums are delicate fruits. Their skin breaks easily, and the stems often fall off. To prevent both of these unwanted occurrences, the wax temperature should be as low as possible (beeswax melting point being around 63°C) as not to cook or break the plum’s skin. Additionally, it is best to select fruits with a strong stem; this makes the dipping process much easier. Hold the stem with a pair of tweezers, dip the plum into the wax, and as soon as the fruit is completely immersed lift it gently out. Keep holding it with the tweezers, and wait a couple of seconds until the wax turns white. Dip again. This should be done 5 times in a row. Then, gently lay the plum on its side and let it rest while you take care of the others. This process should be repeated about 6 times, for a total of 30 layers of wax.


The beeswax layer needs to be thick enough to prevent cracks and leaks which lead to oxidation and a complete ruining of the plum.


A short video of the early process [before we refined it into the technique above]: 

In order to let the fruit ferment, we tied them together with strings and stored them in a dark and cool environment at around 15°C.


Seven days seemed the ideal length of time for these first plums. Cutting one open began with a small hiss of gas, more felt than heard; the open halves revealed flesh bled with pink, softened to a jam, studded with small bubbles of CO2. The texture is soft, supple; the aroma of beeswax suffused through the skin. A mild hint of alcohol, a light acidity, a sparkle of perfused gas. We ate them with spoons, slurped them like oysters, ate them with our hands.


We were thrilled with this wild success. We needed to get more.

We went to Pometet, an orchard created by the University of Copenhagen to preserve and study Danish heirloom fruit varieties, to select some plums for experimentation. They were very generous with us. We decided on eleven different varieties of the ripest and most delicious plums. One would truly be amazed by the ecological and taste diversity of apples, pears, plums, sour cherries, gooseberries, and more that can emerge from such a small country, all of which are preserved on this one plot of land.


Though most, like our first batch, reached their peak after one week, some were ready after two, while others were best after only 5 days and dropped off from there. Some cracked open and oxidised, and others never even really happened. Some developed a banana-like flavour, while others gained a plastic-like taste. Their initial differences were made only more apparent through this process – a huge diversity of sizes, colours, flavours, and textures.

We conducted multiple tastings.


Their characteristics, summarised:

Bella de Septembre: very floral, pleasant

Giant: delicate, sweet, soft

Botrytized (Victoria): wine, bittersweet at the end, complex, very thick and jammy, spreadable, very interesting     

Diamont Blomme: pineapple, metallic, sharp, fibrous, not very interesting, old supermarket plum flavour, plastic taste

Dumiron: prickly, over-ripe banana, unpleasant because of size- not a lot of meat

Anna Spaht: lots of bee wax flavour, tart, sharp, not very sweet, flat

Ungar Svenske: fibrous, bitter, oxidized, cherry flavours

Kraege: pasty, grainy, lots of sediment, bitter, boring

Buhler: apple-y, not very appealing aesthetically, sweet, fall harvest flavours, pruney, meaty, very pleasant. Very small though, not a lot of flesh. 

Grand Duke: sea urchin texture, velvety, jammy, voluptuous, carbonated, very plummy, sparkly, incredibly pleasant

Esslinger: sparkling, sweet, soft finish

Even after testing this technique with a variety of local plums, we still do not understand the process fully. It is likely the fermentation is due to yeast: anaerobic conditions, available sugars, presence of alcohol and carbon dioxide. But there could also be some bacteria. And we have no idea what sorts of yeasts are on which plums – this factor could also be contributing to the differences enhanced through the fermentation. We also need to experiment more with temperature conditions – if we keep them very cool, could we extend the life of the fruit and delay the peak for weeks or months? Or even alter the microbial ecology inside the wax sarcophagus?

What we do know, however, is that some of them tasted ‘fucking delicious' and that we now have to wait until next year to continue the research.


An Older Elder

Added on by Ben Reade.

Part 1 by Ben Reade


Our recipe for elder vinegar. Begun from a elderflower wine and undergoing a second fermentation on the berries, this vinegar has good aging potential. The fermentation makes it safe from any potential cyanide, and the acidity brings out the floral, fruity notes over the muddy, watery ones. It is delicious.

So, sometime in the spring of 2010 while I was living in Italy I got into making elderflower syrups – it’s something I’ve grown up around in Scotland, a favourite taste of summertime. During my childhood, around 50% of the bottles would start to ferment (some would explode) and when a good recipe was stumbled on by chance (my mum would never weigh anything), a delicious sparkling wine would magically appear. Now, elderflower champagne, as it’s often know, is as old as the hills. It’s delicious, always gets consumed faster than expected, and everyone always wishes they had made more.


A good recipe for a traditional elderflower syrup is:

80 heads of elder flowers, removed from green stems (harvested after some days of sunshine)
2.5 L water
3 kg sugar
100 g citric acid
Zest and juice of 6 (*ahem*, nordic) lemons

Boil sugar and water, pour over the rest, cover and leave for 24 h. Strain.

If you want to bottle it to keep as syrup, you can pasteurize it at 63 °C for 30 minutes or 72 °C for 15 seconds before closing in clean bottles. However, you may instead like to take your syrup on a longer journey. For this the options are endless, so I will not give you super precise instructions – also because when I made the best version of this, I was not in ‘lab mode’ and have no written record of any recipe, and it was done by feel. Unrepeatable – as the very best things so often are.

our pollen-dusted hands after picking many bags of elder flowers

our pollen-dusted hands after picking many bags of elder flowers

I’d like to tell you how to turn this into floral vinegar with a gentle acidity and some sweetness, suitable for diverse applications from desserts to sauces and cocktails. This is somewhat similar to a ‘shrub’, but I have never tasted a shrub this good. The fact that it goes through two layers of fermentation, alcoholic with the flowers and acetic with the berries, leads to completely new levels of complexity.

To make your syrup into a wine (the first stage in vinegar-making), dilute it down to around 20% sugar (more to have it sweeter/stronger, less to have it more dry/weaker – dependent on the yeast strains being used), give it a shake to dissolve some oxygen and pitch (add) some yeast. Put an airlock on this and leave it somewhere cool to ferment and forget about it for a while. For more information on alcoholic fermentation, check here.

So in 2010 after tasting my over-sweet, but quite alcoholic and rather nice floral wine, I decided I wanted to make vinegar that had serious aging potential. I’ve been quite obsessed with vinegar for quite some time, so there are a few posts written about it around on this blog. For simple European vinegars see here, processing methods here and balsamic style vinegars, here.

Back to my elder vinegar, and how to get it older. The ‘wine’, as it stands, has a very simple mixture (sugar, water, acids, floral and lemon flavours and alcohol). In order to give the vinegar aging potential it required some structure, tannins and antioxidants. Of course, elderberries are rich in all these things, so it made sense to give the flower wine structure using fruits of the same plant.


So, hold the wine until the elder berries are ripe and deep purple. Then pick loads and loads of the biggest, juiciest berries, and fill up a wide mouthed jar with them. This works well with elderberries, but also with blackberries and other colour-rich berries that will give aging potential to your vinegar. Cover the berries with your elderflower wine, and add about a quarter of this quantity again of live vinegar.


It’s important to use a wide-mouthed jar to increase oxygen circulation, and don’t use a lid but a thin piece of muslin or similar. Keep your slowly processing vinegar in a warm and dark place (between 30 - 40 °C is great). Leave it for 1 month like this. After that time, strain to remove the berries, return to the jar and put back in your warm and dark place for another two months.


Don’t worry if you remove the vinegar mother while straining. Although the mother is attached to lots of superstition, it is a recognizable manifestation of the acetic acid bacteria, but the bacteria are plentiful in the liquid, and that’s quite enough! For more information on the formation of mothers, and how that works, have a look at this excellent post on the acidic beverage kombucha.

There is one problem, and that is that elderberries can be toxic. In fact the whole elder plant is pretty full of a family of molecules called cyanogenic glycosides – which are particularly potent in the green parts and the seeds. For more informations on this, you can refer to Justine's post on hygrogen cyanide. This is why it is crucial to separate the green parts from the flowers when making the syrup.

But then we get to the berries. If one drinks a freshly made elderberry juice, and we tried it, chances are that one is going to feel bad for a little while – to quote René, reflecting on a spoonful of raw elderberry juice, “you know the feeling of car sickness, it’s like that but times 100, it’s like hitting a brick wall of nausea, with immediate effect”  – and we are now older and wiser. So don’t try raw elderberry juice.

So I wanted to find out more about cyanogenic glycosides, and knew that people who had tried the berries had felt very sick, but that people who tried my vinegar had a massive smile.

Luckily we have Justine here at the lab, and she’s great at the chemistry side of things, so she’ll fill you in on that.

And yeah, I know Elderflower season is over, but we'll repost this at the start of next year’s season! 

  Part 2: Is this vinegar safe?
by Justine de Valicourt

here is a long tradition in many areas of the world, particularly Africa and South Africa, of eating cassava. Cassava has one of the highest concentrations of cyanogenic glycosides and it is often the cause of massive food poisoning in regions with drought or famine. Cassava products are harmful mostly in these moments because people are consuming it immediately, before it is properly processed. This root should always be cooked after being previously soaked and fermented. The fermentation lowers the pH and therefore also the potential release of cyanide from the glycosides (White, 1998).

Glycosides are molecules that include a sugar and another functional group. In the case of cyanogenic glycosides, the functional group is partly composed of a molecule of cyanide. They are concentrated in vacuoles (small bubbles distributed throughout the cytoplasm of the cell). When the cell is harmed, the bubbles break and the cyanogenic glycosides are released into the cytoplasm, where they can react with enzymes that will break the bond between the sugar molecule and the functional group. The free cyanide then begins its disturbance of cellular respiration.

The cyanogenic glycosides in elderberries are different from the ones in cassava, but a study from Eugeniusz Pogorzelski (1982) also showed that fermentation lowered the cyanide potential of elderberries. Enzymes are proteins, and acidity does the same to them as to fish in ceviche or as heat does to an egg: it denatures them. Enzyme then become inefficient at breaking the bond between the sugar and the cyanide and the cyanide stays harmless. So, the low pH of the vinegar might be enough to lower the cyanogenic potential of the berries. Could explain the smile...

Also, as hydrogen cyanide evaporates at 26°C, a big part of the free cyanide should be released in the second fermentation that occurs around 30-40°C.

Finally, and importantly, nobody ever drinks an entire glass of vinegar.

So the vinegar is safe of cyanide. Ours is in its second fermentation. It started to oxidise, with that distinctive sherry taste, and a scent reminiscent of the floral notes on a good sweet Moscato di Asti. Soon we will be smiling.



WHITE, Wanda LB, ARIAS-GARZON, Diana I., MCMAHON, Jennifer M., et al.Cyanogenesis in Cassava The Role of Hydroxynitrile Lyase in Root Cyanide Production. Plant Physiology, 1998, vol. 116, no 4, p. 1219-1225.

POGORZELSKI, Eugeniusz. Formation of cyanide as a product of decomposition of cyanogenic glucosides in the treatment of elderberry fruit (Sambucus nigra). Journal of the Science of Food and Agriculture, 1982, vol. 33, no 5, p. 496-498.


Searching for cyanide

Added on by Justine de Valicourt.

by Justine de Valicourt


Cyanide is a strongly toxic compound that is frequent in nature, including in some plants generally considered safe. We investigated its pathway to have a better understanding of its toxicity. A lot of food contains small concentrations of cyanide in the form of glycosides. When the plant is hurt or chewed a chemical reaction occurs in the harmed cell and the cyanide is released as a natural defense. This poison blocks the cell’s uptake of oxygen, bringing on a cellular condition called histotoxic anoxia, lit. ‘cell-toxic lack of oxygen’. The cell is no longer able to produce energy for its normal functions and quickly dies.

The human body can detoxify a small amount of cyanide in the liver through a pathway involving a molecule called thiosulfate. Poisoning occurs when there is not enough thiosulfate to neutralise all the cyanide. At low toxic concentrations the cyanide can provoke nausea, vomiting, general weakness and dizziness. A lethal dose to humans is thought to be 98mg in one day, with a lowest documented lethal dose of 37.8mg.

Cyanide has a boiling point of 25.7°C, which means that even a little heat would vaporise the toxin and make the product safer.

We focused our investigation on the cyanide content of black elder and elderberries. Elder (Sambucus nigra) leaves, bark, roots, unripe fruits and stems contain high levels of cyanide. Completely ripe fruits are generally considered safe to eat. Scientific literature has related few cases of food poisoning from elderberries, but each event was probably brought on by the accidental use of leaves and stems along with the berries.

To satisfy our curiosity on the subject of cyanide, we decided to prepare a common semi-quantitative test to evaluate the level of cyanide in food. The test uses the reaction of picric acid (yellow compound) changing into isopurpuric acid (brown-reddish) in the presence of volatile hydrogen cyanide (HCN). The HCN contained in any solution turns the paper from bright yellow to brick orange. The intensity of the colour change gives a rough idea of the concentration of HCN. A more refined test would be to make a scale of colour with known concentrations of HCN, and then to compare picric acid paper analyses from food products with the colour scale to approximate the food’s HCN concentration.

Elderflower season is over. Their magnificent perfume is no longer around us. We made good use of the season, however, harvesting it wherever we found it. Our different projects involving elderflower have made us think about the safety of consuming the elder plant, its flowers and berries. We knew that elder can be toxic, but were not sure about the circumstances of this toxicity or how best to remove it. Elder, along with other plants like stone fruits and cassava, contains hydrogen cyanide (HCN) in the form of cyanogenic glycosides. This usually inactive molecule is broken down by enzymes when the plant is harmed, or the pit crushed, and hydrogen cyanide is released as a natural repellent against insects and other hungry predators. 

Hydrogen cyanide (from The Atomic Dashboard)

Hydrogen cyanide (from The Atomic Dashboard)

Detoxification and excretion of cyanide [2]

Detoxification and excretion of cyanide [2]

Thiocyanate (from The Atomic Dashboard)

Thiocyanate (from The Atomic Dashboard)

So we began researching toxicity and human tolerance to HCN. It seems that an ‘average’ human could be killed by ingesting 70g of apple seeds. That is a lot of apple in one day. In fact, the body is able to detoxify small amounts of HCN in the liver, through an enzyme called rhodanese [1] that uses a molecule of thiosulfate to bind the cyanide group and render it harmless. The resulting thiocyanate is excreted in the urine, while the free sulphate group is available for another purpose. Poisoning from HCN thus occurs when there is not enough thiosulfate available to neutralise the cyanide.

The Electron Transport Chain

Yet why is cyanide dangerous in the first place? The molecules enter the cell, blocking the complex reaction that transforms oxygen into energy: the electron transport chain.

The electron transport chain on the inner membrane of the mitochondria [6]

The electron transport chain on the inner membrane of the mitochondria [6]

This chain of enzyme complexes is situated in an organelle called the mitochondrion. The mitochondria have a particular structure: they are composed of two membranes – unlike other organelles which have just one – which create an intermembrane space in addition to the inner mitochondrial matrix.

Cross-section of a mitochondrion [wikipedia]

Cross-section of a mitochondrion [wikipedia]

The four types of enzyme complex are attached to the inner membrane of the mitochondria and permit a gradient of electrons to develop between the inner space and the intermembrane space. This gradient is necessary for the final step in the transformation of adenosine diphosphate (ADP) into adenosine triphosphate (ATP) by a fifth enzyme called ATP synthase. ATP synthase attaches a third phosphate group onto ADP using the energy from the electrochemical gradient and the influx of H+ ions. ATP is the body’s chemical energy – almost every metabolic reaction needs it. It is called a co-enzyme because most other enzymes cannot work properly without it. ATP is the currency of the body’s chemical economy. 

The electron transport chain with ATP synthase [7]

The electron transport chain with ATP synthase [7]

The cyanide molecule intervenes in this process, fixing itself to the cytochrome c oxidase, the main enzyme of the fourth enzyme complex, and changing its configuration. This alteration makes it impossible for the complex to transfer H+ ions to the intermembrane space and to synthesise them into water with oxygen. By blocking this crucial step, the cyanide effectively disrupts the entire electron transport chain. ATP is no longer produced in the aerobic conditions and the cells die quickly from a condition called histotoxic anoxia (cellularly toxic lack of oxygen). The first cells to be harmed by the poison are those in organs that cannot perform under anaerobic conditions: first the brain, then the liver and the other vital organs.

Death by apples

The scientific literature relates a few cases of poisoning from fruit consumption: children dying from eating apricot and cherry pits [5]; a women who became poisoned by drinking choke cherry spirit [6]. In the latter case, the spirit and cherries were analysed for HCN content with results of 43-45mg/kg and 4.7-15mg/kg respectively. Although it is quite impracticable to study a lethal dose for humans without killing any, some studies have proposed a potential lethal dose of 1.4mg per kg of body weight, with a lowest lethal dose documented of 0.54mg per kg of body weight1. For an average man of 70kg, this means an ingestion of 37.8mg in one day.

The following table presents different food products and their concentration of HCN [1].

cyanide in food products.png

The crucial fact here is that HCN has a boiling point of 25.7°C. Which means that in preparations involving heat, and even a slight incubation above room temperature, most of the free cyanide will evaporate, leaving the food product much safer.

Beyond these few clear facts, the literature holds a lot of confusion. All sources agree that the elder tree has cyanogenic glycosides and thus the potential for HCN; yet some sources suggest the berries and flowers are safe to eat, some say not really, and some say they should always be heated before consumption. Furthermore, we haven't found any article that clearly states a concentration of HCN in either the berries or the flowers. Which brings us back to our central question: are elderberries safe to eat raw? In what quantities? Do they harbour other toxins that could be harmful when ingested?

A relevant project of ours is an elder vinegar, using elderflower wine and adding the berries before the acetic fermentation (another post on this will come soon). Will this vinegar be safe to consume in large quanities?
After a bit of digging we found that raw elderberries contain 3mg of potential HCN (in the form of glycosides) per 100g of fruit, making them dangerous for cyanide poisoning only with a consumption of more than 1.5kg of raw fruit in a day. While that's quite a bit of berries, it's not out of the realm of possibility – though when we're talking about vinegar, it may be safe if for no other reason than that one rarely drinks a bucketful. Toxicity is always about dose and concentration.

That said, we like to have more precise answers and to be able to see them for ourselves. Through our research we discovered it is quite easy to make our own test to determine the HCN content of any product.

The DIY picric acid test for HCN

Pure picric acid is an explosive. But in solution, it is quite harmless (for an acid). Picric acid itself is bright yellow, but when it reacts with cyanide it is reduced to a more orange-brown compound call isopurpuric acid [7]. By soaking filter paper in picric acid, one can make simple test paper that gives slightly-better-than-binary results. Once dry, the paper will react with HCN vapour, which in practice means that if you put a cyanogenic product in a test tube with some water to soak it, then suspend a strip of this paper at the top of the test tube before closing it, the vapour from the product will interact with the picric acid and make the colour of the paper changes from a bright yellow to an orange-brown. The more cyanide in the product, the browner the paper.

Picric acid (from The Atomic Dashboard)

Picric acid (from The Atomic Dashboard)

Transformation of picric acid (on the left) to isopurpuric acid (on the right) by the addition of CN- [4]

Transformation of picric acid (on the left) to isopurpuric acid (on the right) by the addition of CN- [4]

We made an initial test with cassava to calibrate our paper, as cassava has one of the highest concentrations of HCN in a food product. Here are the results:

HCN test t+2min

HCN test t+2min

HCN test t+1hr

HCN test t+1hr

It works.

The next step is to make graded test strips with solutions of different concentrations of sodium cyanide (NaCN). We will then have a semi-quantitative test because we will be able to use the relative concentration of cyanide in NaCN as a benchmark for comparing the HCN concentration of many different foods. Hopefully we can get it ready before the elder vinegar!

While the HCN in elderberries can poison one to death, it became clear through our investigation that it was not the only source of the common emetic and purgative symptoms of consuming the berries raw. We've since looked further into elder, with more findings to come.

[erratum 2.11.13]
Thanks to Julia Stasinska for spotting an error in the table - 5mg/kg of cyanide in apple seeds is actually 500-700mg/kg.


1          Concise International Chemical Assessment Document 61, HYDROGEN CYANIDE AND CYANIDES: 

2          Wiki Tox, Open Source Clinical Toxicology Curriculum. Cyanide. Online.

3          University of Illinois at Chicago. Glycolysis, Krebs Cycle, and other Energy-Releasing Pathways. Online.

4          Wikimedia Commons. Mitochondrial electron transport chain short PL.svg. Online.

5           Sayre JW, Kaymakcalan S (1964) Cyanide poisoning from apricot seeds among children in Central Turkey. New England Journal of Medicine, 270:1964.

6          Nahrstedt AF (1993) Cyanogenesis and food plants. In: van Beek TA, Breteler H, eds. Proceedings of the International Symposium on Phytochemistry and Agriculture, 22–24 April 1992, Wageningen. Oxford, Oxford University Press, pp. 107–129.

7          The Picric Acid Method for Determining Weak Acid Dissociable (WAD) Cyanide, published by MEP Instruments and Applicon Analyctical®. Online.