Bitterness, Fire and Alkali

by Ben Reade.

Bitterness is a very intriguing taste. Humans are born with an aversion to bitter tastes (Morini, 2007) and through life we learn to appreciate bitterness, many adults actively searching the taste in their food. Bitter tasting molecules are hugely diverse, with little or no chemical characteristics grouping them together as a unit. Bitterness is thought to be a survival mechanism for recognizing toxins in our environment, most poisons are very bitter. As we grow older however humans develop knowledge of what can and cannot be eaten. This knowledge removes some of the need to have an aversion response to the taste and the tendency is that humans start to appreciate bitter taste when it is not too strong. This is useful, as many bitter compounds act as anti-oxidants, which slow the body’s aging.
In NNC, there is a big focus on vegetables, especially green and bitter varieties, often from the botanical family brassicaceae and the multitude of wild herbs all tend to have a certain bitter taste. Bitterness can also be added or removed from dishes though processing technique. Examples of techniques that add a bitter note are the Maillard reactions between amino acids and sugars (especially in the presence of heat). Maillard reactions can be increased in alkali environment, for example, adding a pinch of sodium bicarbonate to browning onions will increase the speed with which they develop the distinctive ‘toasted’ and ‘dark’ flavours.
Smoking, especially of meat, has a long history in Nordic cultures; it has been shown to prevent rapid development of molds, which is particularly important in  humid environments. Toasted grains are also used to stimulate the bitter sense along side the complex aroma the which heat gives to grains. Fire, quite probably, has been the single biggest technology in human development. Throughout the millennia of human history we have been gathered around the fire, we have cooked on it, and possibly learned some kind of innate draw toward the flavour of fire heated foods which are often microbiologically safe and easier to digest. Perhaps it is for this reason that smoked foods and foods cooked above open fire are so very appetizing. At Noma, a considerable amount of food is cooked on open coals, using only the finest charcoal.

Interestingly, Dan Barber’s Blue Hill Farm (Great Barrington, Massachusetts), are making their own charcoal out of a huge variety of organic substances, for example lobster shells, which, when burned, will impart a bit of their flavour onto a cooking lobster. It should be emphasized that open coals, fire and smoke add specific nuances, which have a high acceptability with those eating.

When smoking Atlantic Salmon in Denmark and Norway the wood most frequently used are beach, however many fruits woods such as apple, pear or cherry are also used.. When burning wood, one is inevitably left with considerable quantities of ash. This too has uses, and ashes of different woods, can provide varying flavours to meat. In Nordic Cuisine ash of various plants is used, and especially of hay, to roll meat in, especially charcuterie, in order to add a unique flavour that only fire can produce.

Ash when in water, will form a strongly alkali solution. This can be used for a number of ways: strong alkalis are used in the kitchen and here we show a few of these applications – also closing the circle of this chapter, bringing it all back to bitterness.

There is a tradition in Nordic Countries of using ash from the birch tree (Betula sp.), which is particularly high in potassium carbonate (K2CO3 otherwise known as potash) and bicarbonate. This ash can be used to make a strongly alkali solution, and is recognized by many as a health giving product (it is often sold in health food shops as a dietary supplement. It can be used in the kitchen as a firming agent, due to its precipitation causing effect on residual pectin. In Finland it is the traditional curing agent used in making Lutefisk (Alkali cured salt cod), which, in other places is generally made with lye.

Alkali solutions (particularly of limestone) are used in south-east Asian tradition to crisp up both fruits and vegetables. The crisping of fruits and vegetables occurs by binding free pectin, so works best with pectin rich fruits, especially, citrus, pumpkin and berries. By heating water and ash followed by subsequent straining a saturated solution of potash is obtained, that will have the effect of hardening fruits and vegetables so that they keep their shape during cooking. Other uses for alkali in the kitchen include giving the specific flavour and texture to pretzels, ramen, black olives, hundred year old eggs and the Mesoamerican technique of nixtamalization[1]. Literature review at NLF led to the discovery of numerous accounts of using NaOH as a debittering agent for yeast extracts. We wanted to use natural occurring products and so we experimented with debittering the yeast extract using wood ash for alkalinity, this proved successful (More on this in a later post).

Further use of potash was made upon discovery of documents on  ethnolichenology[2] documents (Crawford, 2000) referring to the traditional practice of soaking lichens in ash solution before cooking. Although unspecified in the reference, from our sensory analysis at NFL of lichen prepared in this way, we found it considerably less bitter (the mechanism of which is unknown). The strong alkali may be instrumental in breaking down indigestible polysaccharides in the lichen. This experiment was carried out with Iceland moss (Cetraria islandica (L.) Arch.), traditionally a famine food of Nordic peoples (see image below). Interestingly, for populations of the far north, lichens may be the only source of dietary greens, due to the fact that these are largely indigestible, some populations eat the lichen from inside the digestive tract of freshly slaughtered reindeer. By consuming them in this way,  the lichen is presumable more easily assimilated by the human body thanks to hydrolyzing work by the reindeer’s digestive enzymes (Nabhan, 2004).

Iceland moss (Cetraria islandica)

[1] Nixtamalization – the process of using alkali to break down maize for making tortillas, it releases nutrients, importantly niacin from the maize, thereby preventing pelagra

[2] Ethnolichenology – The study of the human relationship to, and use of lichens.


Morini, G. (2007) Molecular aspects of taste, Gastronomic Sciences 2 :42.

Nabhan, G.P. (2004) Why some like it hot: food genes and cultural diversity Island Press, USA.

About the author

My Name is Ben Reade, I’m a chef from Edinburgh, Scotland, and for the past 3.5 years I have been studying at The University of Gastronomic Sciences in Pollenzo, Italy. For my final thesis, I came to Nordic Food Lab to research many subjects where my varied interests inerlaced with those of the Lab. The research arose out of time spent at the Nordic Food Lab between 29 September and 22 December 2011. The aim is to describe NFL’s current research to both chefs and non-specialized readers, explaining and coding the creative and scientific methodologies employed during the research at NFL, exploring their application in food experimentation and innovation. Over the next month or so I will be breaking down this thesis into manageable blog-style chunks, this is chunk 4 of around 25 I hope you find it interesting.