Author: Ben Faerman
Before I go into the specifics of certain ferments, I want to give a broader definition. Fermentation comes from the Latin food fervere, meaning “to boil”, and Noma in Copenhagen refers to it as “the transformation of food through enzymes produced by microorganisms, whether bacteria, yeasts, or mold”. It has been used as a method of preservation and flavor enhancement for thousands of years, starting in the Mesopotamia region and China, and chefs today are revolutionizing the variety of products that are subject to this process. According to Arielle Johnson, scholar of food science at MIT:
“Microorganisms live in or on their food source, and biochemically transform it to extract energy, producing metabolites in the process. In general, a pool of larger molecular weight, and usually less flavor-active molecules - like starches and sugars - are transformed into a more diverse group of tastier, smaller molecules, such as amino acids, organic acids, esters, sugars, and aromatic compounds.”
Figure 1: Arielle Johnson's depiction of Noma ferments
Fermentation relies on the control of the environment, specifically the salinity level, moisture content, pH (potentiation of hydrogen ions), and temperature, which affect the activity of the microorganisms. There are thousands of species that act upon substrates, but I will describe some of the most common ones below.
Lactic acid bacteria (LAB) - It is used to lacto ferment sugar into lactic acid as a byproduct. Because they produce acid, they tolerate lower pH environments, and they are halo-tolerant (salt-tolerant) and anaerobic.
Lactobacillus
Leuconostoc
Pediococcus
Lactococcus
Acetic acid bacteria (AAB) - obligate anaerobes (thriving only in non-oxygenated environments, and only use anaerobic respiration) in the family acetobacteraceae that are responsible for vinegar. However, they require oxygen to make acetic acid.
The yeast saccharomyces cerevisiae, which metabolizes sugar into ethyl alcohol and CO2 in alcoholic beverages and bread. It secretes enzymes through the mycelium, a component of fungi, absorbing nutrients from the environment and digesting certain macromolecules. Different strains can be harnessed for different flavors, depending on the substrate which the yeast acts upon.
Salt-tolerant zygosaccharomyces rouxii, which adds flavor complexities to soy sauce
Aspergillus oryzae has amylolytic and proteolytic properties (degrading starch and proteins) that act upon starch sources like rice and barley for various products; it must stay within the 30-35 ̊C range, or it will die. Its ideal humidity is 80%, and it has a lesser known variety, Aspergillus luchuensis, which metabolizes starches and proteins and produces citric acid as a byproduct and is used for awamori and shochu.
Penicillium roqueforti, the mold that adds flavor and “ripens” cheeses, transforming proteins into amino acids and creating unique compounds
Brettanomyces is used in some alcoholic ferments because of its ability to produce acetic acid (HC2H3O2). It can survive on oxygen, but produces ethanol anaerobically, and like other yeasts, it cannot survive temperatures above 60 ̊C/140 ̊F. In many cases, there are two fermentation products, like aspergillus: the first ferment allows a microorganism to break down a starch, producing enzymes that convert them into simple sugars and other metabolites, and the second allows those saccharified starches to act upon proteins and for the microorganisms to further produce flavor compounds.
Figure 2: Anaerobic Respiration in two stages
It's undeniable that fermentation carries health benefits: in many foods, new vitamins are introduced, like cyanocobalamin and pyridoxin (B12 and B6), as well as acetate (vitamin E). Furthermore, certain compounds like anti-nutrients that prevent absorption or raffinose, the compound in beans that causes gas and bloating are rendered inactive through the fermentation process, as microbes consume them as fuel. Although the link has not been proved for certain, there is some evidence in the scientific community that suggests that fermentation can improve the health of the gut microbiome, and improve the immune system's resiliency, which is currently under investigation.
Fermentation has become an intrinsic part of our lives, from cheese to chocolate to bread, and a new wave of this tradition has begun to influence how the restaurant world shapes its cuisine. At Noma, René Redzepi and David Zilber have built an entire fermentation chamber dedicated to researching various ingredients and microorganisms, which they incorporate into their menu. While fermenting at home doesn't have to be as complex as squid garum or black garlic miso, simple saeurkrauts or kimchi can easily be made (and nothing compares to a version you make yourself!).
References:
“Fermentation - an Overview | ScienceDirect Topics.” Accessed November 12, 2020. https://www.sciencedirect.com/topics/biochemistry-genetics-and-molecular-biology/fermentation.
Redzepi, René, and David Zilber. The Noma Guide to Fermentation: Including Koji, Kombuchas, Shoyus, Misos, Vinegars, Garums, Lacto-Ferments, and Black Fruits and Vegetables. Illustrated edition. New York: Artisan, 2018.
“Yeast, Fermentation, Beer, Wine | Learn Science at Scitable.” Accessed November 12, 2020. https://www.nature.com/scitable/topicpage/yeast-fermentation-and-the-making-of-beer-14372813/.