fermentation: Definition and Much More from Answers.com

Fermentation is one of the oldest known food preservation techniques. Along with drying and salting, fermentation was a key method of extending the life of foods, allowing them to be available, and eaten safely, in times of scarcity or seasonal nonavailability. These methods helped allow the transition from hunting and gathering to organized food cultivation and storage, which took place some ten to fifteen thousand years ago in the Middle East.

Fermentation involves the action of desirable microorganisms, or their enzymes, on food ingredients to make biochemical changes, which cause significant modification to the food. Often lactic-acid bacteria convert the carbohydrate energy source of food, such as lactose in milk, to lactic acid; examples are yogurt and cheeses from milk, and pickles from fruits and vegetables. Alternatively, yeasts, often of the Saccharomyces species, may convert the glucose to ethanol and carbon dioxide in leavened breads, or the sugars in grain or fruit beverages to beers and wines. Molds also can be active in certain fermentations, such as Stilton cheese and soy sauce. It is estimated that about one-third of all the food we consume is fermented. World estimates for beer consumption are about 22 million gallons, and a total of 15 million tons of some one thousand varieties of cheese are eaten annually.

Fermented Beverages and Foods

Fermentation is often the key to the safe, enjoyable consumption of perishable food materials, as it changes their composition, flavor, and texture. For example, milk is a nutritious but highly perishable beverage. Originally, in the Middle East, milk carried in animal-skin containers, often on horseback, would sour naturally, to produce acidic fermented milk. The combined action of the two lactic-acid bacteria, Streptococcus lactis, producing lactic acid, and Lactobacillus bulgaricus, producing lactic acid and acetaldehyde, a major contributor to flavor, are involved in yogurt production. The Tartars of Central Asia used the milk of horses, donkeys, or camels to produce a fizzy, gray acidic and alcoholic drink, kumiss, in which yeasts were active.

In acid conditions, the milk protein, casein, denatures and is precipitated to form a curd, producing cottage and soft cheese. By stirring and pressing, whey is removed and a more solid curd is produced, which by ripening or maturation produces semi-hard or hard cheeses. Surface-active bacteria of Brevibacterium linens are active in producing the aroma of Limburger type cheeses, while the blue molds of the genus Penicillium give Stilton and Gorgonzola cheeses their character.

The use of Saccharomyces yeasts has allowed the production of a range of fermented beverages, enabling safe consumption of liquid when fresh water supplies are not available. Lagers, the light golden, gassy beverage made by "bottom" yeast fermentation of cereal extracts, were first made in the regions of Germany and Czechoslovakia, but are now produced and consumed throughout the world. In Africa, a thick, sour alcoholic beverage is made from sorghum or millet, or sometimes maize or banana. These sorghum beers are important sources of nutrients, particularly B vitamins, to people on marginal diets in these regions. The Romans planted extensive vineyards in North Africa to harvest and ferment their grapes into wine, thereby producing a fermented beverage that could be readily stored, transported, and consumed when and where required.

Distillation of these alcoholic beverages, such as whiskey from beers, brandies from grape wines, or arrack from palm or rice wine, further extend our range of drinks and play important cultural roles in festivities.

Fermentation Vessels and Starter Cultures

Art meets science in the production of fermented foods. Traditional practices are passed down through generations of producers, often small in scale, and consumption patterns often have great cultural importance. In Scandinavia, traditionally the brides and mothers jealously guard their own supplies of sourdough starters, so that they can always make the desired bread for their partners and families. In West Africa, a homeowner keeps a supply of dawadawa, a dried fermented African locust bean paste (Parkia species); it is used to give everyday soups and stews the desired "meaty" flavor, while also providing important nutrients, such as riboflavin, the B vitamin that protects against blindness, which is endemic to the region due to nutritional deficiency.

In Korea, few meals are complete without kimchi, a pickled fermented cabbage, which may also contain fish and other components. The practice of every home having their own kimchi jars, often on their verandahs, originated as a way of preserving vegetables through the cold winter season, providing year-round vitamin C. Kimchi together with kochujang, the fermented red pepper paste, give Korean preparations a unique and characteristic attractive color and flavor.

Where food fermentation occurred naturally as conditions favored particular organisms, an important art arose to encourage the desired fermentation organisms, while preventing undesirable microorganisms from developing, for successful fermented food production.

Food storage often took place in earthenware vessels, whose semipermeable inner walls were difficult to clean completely. This allowed a biofilm of desirable microorganisms to remain, to initiate a successful fermentation of the next batch of food. Because of their significance, the vessels themselves were artistically designed and treasured. Interesting examples can be seen in museum collections, such as the Nezu Museum in Tokyo, Japan, and a museum dedicated to kimchi in Seoul, South Korea.

In Europe, the fermented meat producers, while using ceramic or metallic vats with smoother, more easily cleaned surfaces, developed the technique of "backslopping" to introduce a small quantity of the fermenting liquor from the previous batch of meat to initiate successful fermentation.

In many cases, dried grains or balls of the derived fermenting microorganisms on cereal or other substrates would be used to start fermentation. Baker's yeast may be used in this work. Kefir grains are used in North Africa, the Middle East, and Russia for production of kefir, laban, or leben fermented milks. Ragi is used in Indonesia and throughout East and Southeast Asia as inoculum for lao-chao and other fermented foods.

Cultural Diversity

The production, consumption, and enjoyment of different fermented foods reflects the diversity of cultures and cuisines that make up our varied world. In Chinese and Japanese cuisines, shoyu, or soy sauce, is added almost universally to dishes, while the Indian vegetarian diet depends on fermented cereals and legumes, often in combinations, as in dosas and vadas. The art and science of fermenting meat to a wide range of salamis are vital to the enjoyment of Eastern and Central Europeans, while Italian food market stall holders proudly display their mold-covered fermented sausages and traditional cheeses.

As people migrate, they normally carry their traditional fermented food practices with them. The range of fermented cheeses and meats in Latin America reflects the European origins of these populations, and the wineries of Chile were originally established by French families. Consumers of imported wine, chocolate, coffee, or tea are all beneficiaries of the internationalism and significance of fermented foods.

Bibliography

Campbell-Platt, Geoffrey. Fermented Foods of the World: A Dictionary and Guide. London: Butterworth, 1987

Steinkraus, Keith, ed. Handbook of Indigenous Fermented Foods. 2nd ed. NewYork: Marcel Dekker, 1995.

Wood, Brian J. B., ed. Microbiology of Fermented Foods. 2nd ed. London: Blackie, 1998.

—Geoffrey Campbell-Platt