Rennet is a complex set of enzymes produced in the stomachs of ruminant mammals. Chymosin, its key component, is a protease enzyme that curdles the casein in milk. In addition to chymosin, rennet contains other enzymes, such as pepsin and a lipase.
Yogurt is a food produced by bacterial fermentation of milk. Fermentation of sugars in the milk by these bacteria produces lactic acid, which acts on milk protein to give yogurt its texture and characteristic tart flavor. Cow's milk is most commonly used to make yogurt. Milk from water buffalo, goats, ewes, mares, camels, and yaks is also used to produce yogurt. The milk used may be homogenized or not. It may be pasteurized or raw. Each type of milk produces substantially different results.
Salami is a salume consisting of fermented and air-dried meat, typically pork. Historically, salami was popular among Southern, Eastern, and Central European peasants because it can be stored at room temperature for up to 45 days once cut, supplementing a potentially meager or inconsistent supply of fresh meat. Countries and regions across Europe make their own traditional varieties of salami.
Lactic acid fermentation is a metabolic process by which glucose or other six-carbon sugars are converted into cellular energy and the metabolite lactate, which is lactic acid in solution. It is an anaerobic fermentation reaction that occurs in some bacteria and animal cells, such as muscle cells.
Curd is obtained by coagulating milk in a sequential process called curdling. It can be a final dairy product or the first stage in cheesemaking. The coagulation can be caused by adding rennet, a culture, or any edible acidic substance such as lemon juice or vinegar, and then allowing it to coagulate. The increased acidity causes the milk proteins (casein) to tangle into solid masses, or curds. Milk that has been left to sour will also naturally produce curds, and sour milk cheeses are produced this way.
Buttermilk is a fermented dairy drink. Traditionally, it was the liquid left behind after churning butter out of cultured cream. As most modern butter in Western countries is not made with cultured cream but uncultured sweet cream, most modern buttermilk in Western countries is cultured separately. It is common in warm climates where unrefrigerated milk sours quickly.
Cheesemaking is the craft of making cheese. The production of cheese, like many other food preservation processes, allows the nutritional and economic value of a food material, in this case milk, to be preserved in concentrated form. Cheesemaking allows the production of the cheese with diverse flavors and consistencies.
In food processing, fermentation is the conversion of carbohydrates to alcohol or organic acids using microorganisms—yeasts or bacteria—without an oxidizing agent being used in the reaction. Fermentation usually implies that the action of microorganisms is desired. The science of fermentation is known as zymology or zymurgy.
Clabber is a type of soured milk. It is produced by allowing unpasteurized milk to turn sour (ferment) at a specific humidity and temperature. Over time, the milk thickens or curdles into a yogurt-like consistency with a strong, sour flavor. In Joy of Cooking, "Clabber... is milk that has soured to the stage of a firm curd but not to a separation of the whey."
Leuconostoc mesenteroides is a species of lactic acid bacteria associated with fermentation, under conditions of salinity and low temperatures. In some cases of vegetable and food storage, it was associated with pathogenicity. L. mesenteroides is approximately 0.5-0.7 μm in diameter and has a length of 0.7-1.2 μm, producing small grayish colonies that are typically less than 1.0 mm in diameter. It is facultatively anaerobic, Gram-positive, non-motile, non-sporogenous, and spherical. It often forms lenticular coccoid cells in pairs and chains, however, it can occasionally form short rods with rounded ends in long chains, as its shape can differ depending on what media the species is grown on. L. mesenteroides grows best at 30 °C, but can survive in temperatures ranging from 10 °C to 30 °C. Its optimum pH is 5.5, but can still show growth in pH of 4.5-7.0.
Souring is a food preparation technique that causes a physical and chemical change in food by exposing it to an acid. This acid can be added explicitly, or can be produced within the food itself by a microbe, such as Lactobacillus.
Kefir is a fermented milk drink similar to a thin yogurt or ayran that is made from kefir grains, a specific type of mesophilic symbiotic culture. It is prepared by inoculating the milk of cows, goats, or sheep with kefir grains.
Microbial food cultures are live bacteria, yeasts or moulds used in food production. Microbial food cultures carry out the fermentation process in foodstuffs. Used by humans since the Neolithic period fermentation helps to preserve perishable foods and to improve their nutritional and organoleptic qualities. As of 1995, fermented food represented between one quarter and one third of food consumed in Central Europe. More than 260 different species of microbial food culture are identified and described for their beneficial use in fermented food products globally, showing the importance of their use.
Nem chua is a fermented pork dish from Vietnamese cuisine. It is mainly composed of a mixture of lean pork and thin strips of cooked rind, garnished with garlic and chilli. It can take the form of bite-size pieces wrapped individually in aluminum foil and paper, or a kind of cervelat in sealed plastic. Traditionally the leaves of star gooseberry tree, strawberry guava, cluster fig (sung), Ming aralia, the oriental coral tree Erythrina orientalis, or Indian coral tree are used to wrap nem chua, with a thick layer of banana leaves on the outside. It has a sweet-sour taste characteristic of lactic fermentations, a pink color and a firm and elastic texture.
Symbiotic fermentation is a form of fermentation in which multiple organisms interact in symbiosis in order to produce the desired product. For example, a yeast may produce ethanol, which is then consumed by an acetic acid bacterium. Described early on as the fermentation of sugars following saccharification in a mixed fermentation process.
Quark or quarg is a type of fresh dairy product made from milk. The milk is soured, usually by adding lactic acid bacteria cultures, and strained once the desired curdling is achieved. It can be classified as fresh acid-set cheese. Traditional quark can be made without rennet, but in modern dairies small quantities of rennet are typically added. It is soft, white and unaged, and usually has no salt added.
Sour cream is a dairy product obtained by fermenting regular cream with certain kinds of lactic acid bacteria. The bacterial culture, which is introduced either deliberately or naturally, sours and thickens the cream. Its name comes from the production of lactic acid by bacterial fermentation, which is called souring. Crème fraîche is one type of sour cream with a high fat content and less sour taste.
Carbonated milk or soda milk is a carbonated soft drink. It can be made from powdered milk or fresh milk, and often has added flavor. In addition to modified mouthfeel, carbonated milk also has a longer shelf-life than similarly processed flat milk and a different flavor. It is sold by several companies and is most popular in Asia.
Leuconostoc lactis is a species of lactic acid bacteria that performs fermentation in acidic conditions, like those found in dairy products such as cheese and yogurt, and tend to culture best at moderate temperatures around 30°C. L. lactis typically produces volatile butter-like compounds that are typically used in fermented dairy products, as well as dextran-like exopolysaccharide in sourdough.
