Dairy products or milk products, also known as lacticinia, are food products made from milk. The most common dairy animals are cow, water buffalo, nanny goat, and ewe. Dairy products include common grocery store food around the world such as yogurt, cheese, milk and butter. A facility that produces dairy products is known as a dairy. Dairy products are consumed worldwide to varying degrees. Some people avoid some or all dairy products because of lactose intolerance, veganism, or other health reasons or beliefs.
Yogurt is a food produced by bacterial fermentation of milk. The bacteria used to make yogurt are known as yogurt cultures. 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 the milk most commonly used to make yogurt. Milk from water buffalo, goats, ewes, mares, camels, and yaks are 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.
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.
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.
Lactobacillus bulgaricus is the main bacterium used for the production of yogurt. It also plays a crucial role in the ripening of some cheeses, as well as in other processes involving naturally fermented products. It is defined as homofermentive lactic acid bacteria due to lactic acid being the single end product of its carbohydrate digestion. It is also considered a probiotic.
Lactococcus is a genus of lactic acid bacteria that were formerly included in the genus Streptococcus Group N1. They are known as homofermenters meaning that they produce a single product, lactic acid in this case, as the major or only product of glucose fermentation. Their homofermentative character can be altered by adjusting environmental conditions such as pH, glucose concentration, and nutrient limitation. They are gram-positive, catalase-negative, non-motile cocci that are found singly, in pairs, or in chains. The genus contains strains known to grow at or below 7˚C.
Lactococcus lactis is a gram-positive bacterium used extensively in the production of buttermilk and cheese, but has also become famous as the first genetically modified organism to be used alive for the treatment of human disease. L. lactis cells are cocci that group in pairs and short chains, and, depending on growth conditions, appear ovoid with a typical length of 0.5 - 1.5 µm. L. lactis does not produce spores (nonsporulating) and are not motile (nonmotile). They have a homofermentative metabolism, meaning they produce lactic acid from sugars. They've also been reported to produce exclusive L-(+)-lactic acid. However, reported D-(−)-lactic acid can be produced when cultured at low pH. The capability to produce lactic acid is one of the reasons why L. lactis is one of the most important microorganisms in the dairy industry. Based on its history in food fermentation, L. lactis has generally recognized as safe (GRAS) status, with few case reports of it being an opportunistic pathogen.
Filmjölk, also known as fil, is a traditional fermented milk product from Sweden, and a common dairy product within most of the Nordic countries. It is made by fermenting cow's milk with a variety of bacteria from the species Lactococcus lactis and Leuconostoc mesenteroides. The bacteria metabolize lactose, the sugar naturally found in milk, into lactic acid, which means people who are lactose intolerant can tolerate it better than other dairy products. The acid gives filmjölk a sour taste and causes proteins in the milk, mainly casein, to coagulate, thus thickening the final product. The bacteria also produce a limited amount of diacetyl, a compound with a buttery flavor, which gives filmjölk its characteristic taste.
Crème fraîche is a dairy product, a soured cream containing 10–45% butterfat, with a pH of approximately 4.5. It is soured with a bacterial culture. European labeling regulations specify the two ingredients must be cream and bacterial culture. It is served over fruit and baked goods, as well as being added to soups and sauces. It is used in a variety of other recipes. Sour cream is a similar foodstuff, except that crème fraîche is less sour and has a higher fat content. Sour cream may contain thickening agents not permitted in crème fraîche in many jurisdictions.
Skyr is a traditional Icelandic cultured dairy product. It has the consistency of strained yogurt, but a milder flavor. Skyr can be classified as a fresh sour milk cheese, similar to curd cheese consumed like a yogurt in the Baltic states, the Low Countries, Germany and Russia. It has been a part of Icelandic cuisine for centuries.
Lactobacillales are an order of gram-positive, low-GC, acid-tolerant, generally nonsporulating, nonrespiring, either rod-shaped (bacilli) or spherical (cocci) bacteria that share common metabolic and physiological characteristics. These bacteria, usually found in decomposing plants and milk products, produce lactic acid as the major metabolic end product of carbohydrate fermentation, giving them the common name lactic acid bacteria (LAB).
In food processing, fermentation is the conversion of carbohydrates to alcohol or organic acids using microorganisms—yeasts or bacteria—under anaerobic (oxygen-free) conditions. Fermentation usually implies that the action of microorganisms is desired. The science of fermentation is known as zymology or zymurgy.
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.
Matzoon or matsoni is a fermented milk product of Armenian origin, distributed in Armenia and Georgia. The so-called Caspian Sea yogurt circulated and commercialized in Japan is sometimes said to be the same type of yogurt as matzoon, but a comparison of microbiota and viscosity found that the two are entirely different.
Fermented milk products or fermented dairy products, also known as cultured dairy foods, cultured dairy products, or cultured milk products, are dairy foods that have been made by fermenting milk with lactic acid bacteria such as Lactobacillus, Lactococcus, and Leuconostoc. The fermentation process increases the shelf life of the product while enhancing its taste and improving the digestibility of its milk. There is evidence that fermented milk products have been produced since around 10,000 BC. A range of different Lactobacilli strains has been grown in laboratories allowing for many cultured milk products with different flavors and characteristics.
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.
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.
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.
