Fermentation — the ancient craft in the modern kitchen

Fermentation is one of humanity's oldest cooking techniques and was originally a way to make raw materials durable over the winter months. In recent years, the technique has received renewed attention in professional kitchens, driven in part by restaurants like Noma, where chef René Redzepi and development chef David Zilber have systematized and spread the methods through their work with the fermentation laboratory. Today fermentation is used not only to preserve, but equally to add flavour, acidity and depth to dishes.

§Lactic acid fermentation — the most common principle

With lactic acid fermentation (also called lactic acid fermentation) naturally occurring lactic acid bacteria transform sugars in the raw material to lactic acid. The rising acid lowers the raw material's pH value which both gives the characteristic sour taste and at the same time inhibits the growth of unwanted microorganisms. The technique is classically used for vegetables such as cabbage (sauerkraut) cucumber and carrot but also for fruit and even certain forms of fish.

• 01The vegetables are cut or left whole and placed in a brine or salted directly.
• 02The salt draws liquid out of the cells and creates an environment where lactic acid bacteria thrive while unwanted bacteria are inhibited.
• 03The container is held below the surface of the liquid (e.g. with a weight) to minimize air contact and mould risk.
• 04Fermentation typically stands at room temperature for days to weeks, depending on raw material and desired acidity.
• 05When the taste is as desired, the ferment is moved to cold to slow the process.

§Other forms of fermentation in the kitchen

Beyond lactic acid fermentation, there are several other techniques that professional kitchens work with: acetic acid fermentation (as in vinegar production), alcohol fermentation (beer, wine) and mould-based fermentation with koji fungus used to break down protein and starch in for example garum and miso-like products. What they all have in common is that microorganisms do the work — the chef simply creates the right conditions and controls the process.

§Taste as a result of fermentation

Fermented products contribute umami, acidity and complexity that are difficult to achieve otherwise. A fermented vegetable layer can be used as a tart dressing base, a fermented fruit purée can add depth to a dessert sauce, and garum — a fermented protein liquid related to fish sauce — is used in many modern Nordic kitchens to give dishes an umami lift without being able to taste the individual ingredient directly.

§From tradition to new craft

Although fermentation today is often associated with the new Nordic kitchen the technique is far older and is found in food traditions around the world — from Danish pickling and salting to Korean kimchi and Japanese miso. For a gastronome fermentation is therefore both a rediscovery of old craft and a modern tool for creating flavour without adding artificial flavourings.

“Fermentation is time that works for the cook.”

— Nordic standard that makes cleaning quality measurable