Fermentation in food processing

Fermentation in food processing turns carbohydrates into alcohol or organic acids through the action of yeasts or bacteria, without an oxidizing agent. This field of study is called zymology or zymurgy. The process is older than recorded history; the oldest known evidence of fermentation comes from a 13,000-year-old beer-like residue, with a gruel-like consistency, discovered in a cave near Haifa, Israel.

Humans have used fermentation since ancient times, likely stumbling upon it by accident. To preserve surplus food, people stored items in containers that were probably forgotten, allowing yeast and bacteria to grow naturally. Other early alcoholic drinks include a mix of fruit, rice, and honey from the Neolithic Chinese village of Jiahu (7000–6600 BC). Winemaking began around 6000 BC in Georgia, in the Caucasus region. Seven-thousand-year-old wine jars, now at the University of Pennsylvania, were excavated in Iran’s Zagros Mountains. Strong evidence also shows fermented alcoholic drinks were made in Babylon (circa 3000 BC), ancient Egypt (circa 3150 BC), pre-Hispanic Mexico (circa 2000 BC), and Sudan (circa 1500 BC).

The science of fermentation took a major step forward in 1856, when French chemist Louis Pasteur linked yeast to the process. Studying how yeast converts sugar to alcohol, Pasteur concluded that a “vital force” within living yeast cells—which he called “ferments”—catalyzed the reaction. He wrote that alcoholic fermentation is tied to the life and organization of yeast cells, not to their death or decay.

However, living yeast cells turned out not to be essential. In 1897, German chemist Eduard Buchner of Humboldt University of Berlin showed that sugar could ferment without any living yeast present, thanks to an enzyme complex he named zymase, secreted by the yeast. He won the Nobel Prize in Chemistry in 1907 for this discovery of “cell-free fermentation.” A year earlier, in 1906, studies of ethanol fermentation led to the early identification of oxidized nicotinamide adenine dinucleotide (NAD+).

The byproducts of food fermentation—alcohol, preservative organic acids, and carbon dioxide—all have human uses. Alcohol turns fruit juices into wine, grains into beer, and starchy foods like potatoes into spirits such as gin and vodka. Carbon dioxide leavens bread. Organic acids preserve and flavor vegetables and dairy products.

Fermentation serves five main purposes: enriching diets with diverse flavors, aromas, and textures; preserving large amounts of food through lactic acid, alcohol, acetic acid, and alkaline fermentations; adding protein, essential amino acids, and vitamins to food substrates; removing antinutrients; and cutting cooking time and fuel use.

Fermented beverages have likely always been tied to ceremonies and festivals. Evidence for this comes from the design of drinkware and the residues left inside them.

Fermented foods vary widely by region. Worldwide examples include alcohol (beer, wine), vinegar, olives, yogurt, bread, and cheese. In East and Southeast Asia, there are amazake, atchara, belacan, burong mangga, com ruou, doenjang, douchi, fish sauce, lah pet, lambanog, kimchi, kombucha, leppet-so, narezushi, miso, nata de coco, nattō, ngapi, oncom, padaek, pla ra, prahok, ruou nep, sake, shrimp paste, soju, soy sauce, stinky tofu, tape, tempeh, tempoyak, and zha cai. Central Asia offers kumis, kefir, shubat, and qatiq (yogurt). South Asia features achar, appam, dosa, dhokla, dahi (yogurt), idli, mixed pickle, ngari, sinki, tongba, and paneer. Africa has garri, injera, laxoox, mageu, ogi, ogiri, and iru. The Americas contribute chicha, chocolate, vanilla, hot sauce, tepache, tibicos, pulque, muktuk, kiviak, and parakari. The Middle East includes torshi and boza. Europe offers sourdough bread, elderberry wine, kombucha, pickling, rakfisk, sauerkraut, pickled cucumber, surströmming, mead, kvass, salami, sucuk, prosciutto, and cultured milk products such as quark, kefir, filmjölk, crème fraîche, smetana, skyr, rakı, tupí, and żur. Oceania has poi and kānga pirau.

Fermented foods can also be grouped by base ingredient. Bean-based items include cheonggukjang, doenjang, douchi, fermented bean curd, miso, natto, soy sauce, stinky tofu, tempeh, oncom, soybean paste, Beijing mung bean milk, kinama, iru, and thua nao. Grain-based foods include amazake, beer, bread, choujiu, gamju, injera, kvass, makgeolli, murri, ogi, rejuvelac, sake, sikhye, sourdough, sowans, rice wine, malt whisky, grain whisky, idli, dosa, Bangla (drink), vodka, boza, and chicha. Vegetable-based items include kimchi, mixed pickle, sauerkraut, Indian pickle, gundruk, and tursu. Fruit-based products include wine, vinegar, cider, perry, brandy, atchara, nata de coco, burong mangga, asinan, pickling, vişinată, chocolate, rakı, and aragh.