Fermentation (food)

Beer fermenting at a brewery

Fermentation in food processing typically is the conversion of carbohydrates to alcohols and carbon dioxide or organic acids using yeasts, bacteria, or a combination thereof, under anaerobic conditions. Fermentation in simple terms is the chemical conversion of sugars into ethanol. The science of fermentation is also known as zymology, or zymurgy.

Fermentation usually implies that the action of microorganisms is desirable, and the process is used to produce alcoholic beverages such as wine, beer, and cider. Fermentation is also employed in the leavening of bread (CO₂ produced by yeast activity), and for preservation techniques to produce lactic acid in sour foods such as sauerkraut, dry sausages, kimchi and yogurt, or vinegar (acetic acid) for use in pickling foods.

See also: History of wine and History of beer

Natural fermentation precedes human history. Since ancient times, however, humans have been controlling the fermentation process. The earliest evidence of winemaking dates from eight thousand years ago, in Georgia, in the Caucasus area. Seven-thousand-year-old jars containing the remains of wine have been excavated in the Zagros Mountains in Iran, which are now on display at the University of Pennsylvania. There is strong evidence that people were fermenting beverages in Babylon circa 3000 BC, ancient Egypt circa 3150 BC, pre-Hispanic Mexico circa 2000 BC, and Sudan circa 1500 BC.

French chemist Louis Pasteur was the first known zymologist, when in 1856 he connected yeast to fermentation. Pasteur originally defined fermentation as "respiration without air". Pasteur performed careful research and concluded:

"I am of the opinion that alcoholic fermentation never occurs without simultaneous organization, development and multiplication of cells, ... . If asked, in what consists the chemical act whereby the sugar is decomposed, ... , I am completely ignorant of it."

Contributions to biochemistry

Main articles: History of biochemistry and NADH#History

When studying the fermentation of sugar to alcohol by yeast, Louis Pasteur concluded that the fermentation was catalyzed by a vital force, called "ferments," within the yeast cells. The "ferments" were thought to function only within living organisms. "Alcoholic fermentation is an act correlated with the life and organization of the yeast cells, not with the death or putrefaction of the cells," he wrote.

Nevertheless, it was known that yeast extracts can ferment sugar even in the absence of living yeast cells. While studying this process in 1897, Eduard Buchner of Humboldt University of Berlin, Germany, found that sugar was fermented even when there were no living yeast cells in the mixture, by a yeast secretion that he termed zymase. In 1907 he received the Nobel Prize in Chemistry for his research and discovery of "cell-free fermentation."

One year prior, in 1906, ethanol fermentation studies led to the early discovery of NAD⁺.

Uses

The primary benefit of fermentation is the conversion of sugars and other carbohydrates, e.g., converting juice into wine, grains into beer, carbohydrates into carbon dioxide to leaven bread, and sugars in vegetables into preservative organic acids.

Food fermentation has been said to serve five main purposes:

• Enrichment of the diet through development of a diversity of flavors, aromas, and textures in food substrates
• Preservation of substantial amounts of food through lactic acid, alcohol, acetic acid and alkaline fermentations
• Biological enrichment of food substrates with protein, essential amino acids, essential fatty acids, and vitamins
• Elimination of antinutrients
• A decrease in cooking time and fuel requirement

Fermented foods by region

Nattō, a Japanese fermented soybean food

• Worldwide: alcohol, wine, vinegar, olives, yogurt, bread, cheese
• Asia
  • East and Southeast Asia: amazake, asinan, atchara, bai-ming, belacan, burong mangga, com ruou, dalok, doenjang, douchi, jeruk, lambanog, kimchi, kombucha, leppet-so, narezushi, miang, miso, nata de coco, nata de pina, natto, naw-mai-dong, oncom, pak-siam-dong, paw-tsaynob, prahok, ruou nep, sake, seokbakji, soju, soy sauce, stinky tofu, szechwan cabbage, tai-tan tsoi, chiraki, tape, tempeh, totkal kimchi, yen tsai, zha cai
  • Central Asia: kumis (mare milk), kefir, shubat (camel milk)
  • South Asia: achar, appam, dosa, dhokla, dahi (yogurt), idli, kaanji, mixed pickle, u-to-nga, jaand (rice beer), sinki, tongba, panir
• Africa: fermented millet porridge, garri, hibiscus seed, hot pepper sauce, injera, lamoun makbouss, laxoox, mauoloh, msir, mslalla, oilseed, ogi, ogili, ogiri
• Americas: sourdough bread, cultured milk, chicha, elderberry wine, kombucha, pickling (pickled vegetables), sauerkraut, lupin seed, oilseed, chocolate, vanilla, tabasco, tibicos, pulque
• Middle East: kushuk, lamoun makbouss, mekhalel, torshi, boza
• Europe: rakfisk, sauerkraut, pickled cucumber, surströmming, mead, elderberry wine, salami, prosciutto, cultured milk products such as quark, kefir, filmjölk, crème fraîche, smetana, skyr.
• Oceania: poi, kaanga pirau (rotten corn), sago

Fermented foods by type

Bean-based

Cheonggukjang, doenjang, miso, natto, soy sauce, stinky tofu, tempeh, soybean paste, Beijing mung bean milk.

Grain-based

Batter made from rice and lentil (Vigna mungo) prepared and fermented for baking idlis and dosas

Amazake, beer, bread, choujiu, gamju, injera, kvass, makgeolli, murri, ogi, sake, sikhye, sourdough, sowans, rice wine, malt whisky, grain whisky, idli, dosa, vodka.

Vegetable-based

Kimchi, mixed pickle, sauerkraut, Indian pickle

Fruit-based

Wine, vinegar, cider, perry, brandy, atchara, nata de coco, burong mangga, asinan, pickling, vişinată

Honey-based

Mead, metheglin

Dairy-based

Cheese, kefir, kumis (mare milk), shubat (camel milk), cultured milk products such as quark, filmjölk, crème fraîche, smetana, skyr, yogurt

Fish-based

Bagoong, faseekh, fish sauce, Garum, Hákarl, jeotgal, rakfisk, shrimp paste, surströmming, shidal

Meat-based

Jamón ibérico, Chorizo, Salami, pepperoni

Tea-based

Kombucha

Risks of consuming fermented foods

Alaska has witnessed a steady increase of cases of botulism since 1985. It has more cases of botulism than any other state in the United States of America. This is caused by the traditional Eskimo practice of allowing animal products such as whole fish, fish heads, walrus, sea lion and whale flippers, beaver tails, seal oil, birds, etc., to ferment for an extended period of time before being consumed. The risk is exacerbated when a plastic container is used for this purpose instead of the old-fashioned method, a grass-lined hole, as the botulinum bacteria thrive in the anaerobic conditions created by the air-tight enclosure in plastic.

See also

• Bletting
• Brewing
• Corn smut
• Fermentation (biochemistry)
• Fermentation (wine)
• Fermentation lock
• Food microbiology
• Industrial fermentation
• Industrial microbiology
• Winemaking
• Yeast
• Category:Fermented beverages
• Lactic acid bacteria

External links

• Fermentations in world food processing (1st part, PDF file)
• Fermentations in world food processing (2nd part, PDF file)
• Science aid: Fermentation - Process and uses of fermentation
• Fermented cereals. A global perspective - FAO 1999