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Fermentation in food processing

Fermentation in food processing is the conversion of carbohydrates to alcohols and carbon dioxide or organic acids using yeasts, bacteria, or a combination thereof, under anaerobic conditions. Fermentation usually implies that the action of microorganisms is desirable. The science of fermentation is also known as zymology or zymurgy.

The term "fermentation" is sometimes used to specifically refer to the chemical conversion of sugars into ethanol, a process which 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); in preservation techniques to produce lactic acid in sour foods such as sauerkraut, dry sausages, kimchi, and yogurt; and in pickling of foods with vinegar (acetic acid).

Natural fermentation precedes human history. Since ancient times, however, humans have been controlling the fermentation process. The earliest evidence of an alcoholic beverage, made from fruit, rice, and honey, dates from 7000–6600 BCE, in the Neolithic Chinese village of Jiahu,[1] and winemaking dates from 6000 BCE, in Georgia, in the Caucasus area.[2] Seven-thousand-year-old jars containing the remains of wine, now on display at the University of Pennsylvania, were excavated in the Zagros Mountains in Iran. [3] There is strong evidence that people were fermenting beverages in Babylon circa 3000 BC,[4] ancient Egypt circa 3150 BC,[5] pre-Hispanic Mexico circa 2000 BC,[4] and Sudan circa 1500 BC.[6]

French chemist Louis Pasteur was the first known zymologist, when in 1856 he connected yeast to fermentation.[7] 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

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,"[8] 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,[9] by a yeast secretion that he termed zymase.[10] 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+.[11]


File:Beer and bread.jpg
Beer and bread, two major uses of fermentation in food

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

Food fermentation has been said to serve five main purposes:[12]

  • 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, and vitamins
  • Elimination of antinutrients
  • A decrease in cooking time and fuel requirement

Fermented foods by region

File:Natto mixed.jpg
Nattō, a Japanese fermented soybean food

Fermented foods by type


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


Proofing (baking technique)


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, rejuvelac, sake, sikhye, sourdough, sowans, rice wine, malt whisky, grain whisky, idli, dosa, vodka, boza

Vegetable based

Kimchi, mixed pickle, sauerkraut, Indian pickle, gundruk

Fruit based

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

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

File:Chin som mok.JPG
Chin som mok is a northern Thai speciality made with grilled, banana leaf-wrapped pork (both skin and meat) that has been fermented with glutinous rice

Jamón ibérico, Chorizo, Salami, Sucuk, Pepperoni, Nem chua, Som moo

Tea based

Pu-erh tea, Kombucha

Risks of consuming fermented foods

Alaska has witnessed a steady increase of cases of botulism since 1985.[13] 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, traditional method, a grass-lined hole, as the botulinum bacteria thrive in the anaerobic conditions created by the air-tight enclosure in plastic.[13]

The World Health Organization has classified pickled foods as a possible carcinogen, based on epidemiological studies.[14] Other research found that fermented food contains a carcinogenic by-product, ethyl carbamate (urethane).[15][16] "A 2009 review of the existing studies conducted across Asia concluded that regularly eating pickled vegetables roughly doubles a person's risk for esophageal squamous cell carcinoma."[17]

See also


  1. ^ McGovern, P. E.; Zhang, J.; Tang, J.; Zhang, Z.; Hall, G. R.; Moreau, R. A.; Nunez, A.; Butrym, E. D.; Richards, M. P.; Wang, C. -S.; Cheng, G.; Zhao, Z.; Wang, C. (2004). "Fermented beverages of pre- and proto-historic China". Proceedings of the National Academy of Sciences 101 (51): 17593–17598. PMC 539767. PMID 15590771. doi:10.1073/pnas.0407921102.  edit
  2. ^ "8,000-year-old wine unearthed in Georgia". The Independent. 2003-12-28. Retrieved 2007-01-28. 
  3. ^ "Now on display ... world's oldest known wine jar". Retrieved 2007-01-28. 
  4. ^ a b "Fermented fruits and vegetables. A global perspective". FAO Agricultural Services Bulletins - 134. Archived from the original on January 19, 2007. Retrieved 2007-01-28. 
  5. ^ Cavalieri, D; McGovern P.E.; Hartl D.L.; Mortimer R.; Polsinelli M. (2003). "Evidence for S. cerevisiae fermentation in ancient wine." (PDF). Journal of Molecular Evolution. 57 Suppl 1: S226–32. PMID 15008419. doi:10.1007/s00239-003-0031-2. 15008419. Archived from the original (PDF) on April 17, 2007. Retrieved 2007-01-28. 
  6. ^ Dirar, H., (1993), The Indigenous Fermented Foods of the Sudan: A Study in African Food and Nutrition, CAB International, UK
  7. ^ "Fermentation" (PDF). 
  8. ^ Dubos J. (1951). "Louis Pasteur: Free Lance of Science, Gollancz. Quoted in Manchester K. L. (1995) Louis Pasteur (1822–1895)--chance and the prepared mind.". Trends Biotechnol 13 (12): 511–515. PMID 8595136. doi:10.1016/S0167-7799(00)89014-9. 
  9. ^ Nobel Laureate Biography of Eduard Buchner at
  10. ^ "The Nobel Prize in Chemistry 1929". Retrieved 2007-01-28. 
  11. ^ Harden, A; Young, WJ (October 1906). "The Alcoholic Ferment of Yeast-Juice". Proceedings of the Royal Society of London (Series B, Containing Papers of a Biological Character ed.) 78 (526): pp. 369–375. 
  12. ^ Steinkraus, K. H., Ed. (1995). Handbook of Indigenous Fermented Foods. New York, Marcel Dekker, Inc.
  13. ^ a b "Why does Alaska have more botulism". Centers for Disease Control and Prevention (U.S. federal agency). Retrieved 18 July 2011. 
  14. ^ "Agents Classified by the IARC Monographs, Volumes 1–105" (PDF). International Agency for Research on Cancer (United Nations World Health Organization agency). Retrieved 10 October 2012. 
  15. ^ "Fermented Food : contains carcinogenic ethyl carbamate (urethane)". Live in Green Company Limited. Retrieved 10 October 2012. 
  16. ^ "New Link Between Wine, Fermented Food And Cancer". ScienceDaily. Retrieved 10 October 2012. 
  17. ^ "The WHO Says Cellphones—and Pickles—May Cause Cancer". Slate. Retrieved 10 October 2012. 

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