What Does Lactic Acid Fermentation Create?
Lactic acid fermentation is the process by which bacteria digest sugars and release acids as a by-product of this carbohydrate consumption. These different strains of bacteria are utilized in a wide variety of food preparations, from dairy products like yogurt, to pickled vegetables such as sauerkraut and kimchi, and as starter cultures in sourdough bread.
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Food History
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Lactic acid fermentation has been used in food production for thousands of years. Dairy consumables such as yogurt and kefir were eaten by European tribes thousands of years ago. Fermentation in the form of pickling has also been practiced in Asia for hundreds of years, specifically as a means of preserving food against spoilage. Pickling vegetables was also practiced in Europe in the form of pickled cabbage.
Lactic Acid Bacteria
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There are several kinds of bacilli that are used in lactose acid food fermentation, such as streptococcus thermophilus, lactobacillus casei and lactobacillus bulgaricus. Known commonly as lactic acid bacteria, these various strains used in food products are non-pathogenic. Lactic acid bacteria can further be classified as "homofermentative," meaning that only lactic acid is the end result of fermentation, or "heterofermentative," where other compounds in addition to lactic acid are produced.
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Fermentation
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Because lactic acid fermentation is done without oxygen, it is referred to as an "anaerobic" process. The metabolic pathway of fermentation begins with bacilli consuming sugars present in foods such as glucose, lactose or sucrose and splitting them into smaller molecules of pyruvic acid. These are then further metabolized into molecules of either just lactic acid or lactic acid plus acetic acid and alcohol, depending on the type of sugar being metabolized. Homofermentation converts hexose sugars such as lactose, glucose and sucrose into just lactic acid; heterofermentation converts pentose sugars such as fructose into lactic acids, ethanol and acetic acid.
Fermented Foods
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Acids produced during fermentation in dairy cause proteins to coagulate, leading to curds and a thickening of the milk texture. Examples of fermented dairy are yogurt and kefir. Lactic acid fermentation is also used to preserve foods such as cabbage in the form of sauerkraut and kimchi. Pickling foods retards spoilage because harmful bacteria (unlike lactose acid bacterial strains) cannot survive in an acidic environment. Other foods that can be fermented with lactic acid bacteria are cereals, meats and fish. Sourdough bread starter cultures also contain lactic acid bacteria.
Benefits
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One of the health benefits of consuming fermented foods is easier digestibility. Fermented dairy products such as yogurt and kefir can be eaten by people who are lactose-intolerant because the lactose sugars have been removed and converted into acids by the bacteria. As well as being free of pathogens, fermented foods also retain most of the vitamins that would ordinarily be lost because of high heat during cooking.
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References
- Photo Credit spicy kimchi image by Lucid_Exposure from Fotolia.com
