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Bitter symphony

Techniques and applications that help understand an increasingly popular flavour. Not only up North

Iceland moss (Cetraria islandica), traditionally a

Iceland moss (Cetraria islandica), traditionally a famine food for Nordic peoples. Largely indigestible, some populations eat lichen from inside the digestive tract of freshly slaughtered reindeer: it’s easier for the human body to assimilate them thanks to the hidrolyzing work by the reindeer’s digestive enzymes

Bitterness is a very intriguing taste. Humans are born with an aversion to bitter tastes 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.

Felling a birch tree to burn

Felling a birch tree to burn

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 Nordic cuisine, 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 aminoacids 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.

Smoked Atlantic Salmon, Scotland

Smoked Atlantic Salmon, Scotland

When smoking Atlantic Salmon in Denmark and Norway the wood most frequently used is beech, 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*. Literature review at NFL 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. 

Moss and Cep: reindeer moss with porcini mushroom powder. Served with a crème fraîche dip, it’s one of the most renowned dishes at Noma in Copenhagen

Moss and Cep: reindeer moss with porcini mushroom powder. Served with a crème fraîche dip, it’s one of the most renowned dishes at Noma in Copenhagen

Further use of potash was made upon discovery of documents on ethnolichenology** documents 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. 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).

*Nixtamalization: the process of using alkali to break down maize for making tortillas, it releases nutrients, importantly niacin from the maize, thereby preventing pellagra

** Ethnolichenology: the study of the relationship between lichens and people.

Nordic Food Lab

The most interesting experiments held in the Nordic Food Lab in Copenhagen, housed, since 2009, in a boat moored in front of René Redezpi’s Noma


Ben Reade

Born in Edinburgh, head of culinary research and development at the Nordic Food Lab, he spends his time navigating the world through his nose and mouth

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