Yoghurt or yogurt, or less commonly yoghourt, joghurt (in German) or yogourt (see spelling differences), is a dairy product produced by bacterial fermentation of milk. Any sort of milk may be used to make yoghurt, but modern production is dominated by cow's milk. It is the fermentation of milk sugar (lactose) into lactic acid that gives yoghurt its gel-like texture and characteristic tang. It is often sold in a fruit, vanilla, or chocolate flavor, but can also be unflavored.
Yoghurt remained primarily a food of India, Central Asia, Western Asia, South Eastern Europe and Central Europe until the 1900s, when a Russian biologist named Ilya Ilyich Mechnikov theorized that heavy consumption of yoghurt was responsible for the unusually long lifespans of Bulgarian peasants. Believing Lactobacillus to be essential for good health, Mechnikov worked to popularize yoghurt as a foodstuff throughout Europe. It fell to a Spanish entrepreneur named Isaac Carasso to industrialise the production of yoghurt. In 1919 he started a commercial yoghurt plant in Barcelona, naming the business Danone after his son — better known in the United States as 'Dannon'.
Yoghurt with added fruit marmalade was invented (and patented) in 1933 in dairy Radlická Mlékárna in Prague. The original intention of this combination was to protect yoghurt better against decay.
Yoghurt was first commercially produced and sold in the United States in 1929 by Armenian immigrants, Rose and Sarkis Colombosian, whose family business later became Colombo Yogurt.
Yoghurt making involves the introduction of specific bacteria into milk under controlled (very carefully in industrial settings) temperature and environmental conditions. The bacteria ingest the natural milk sugars and release lactic acid as a waste product; the increased acidity, in turn, causes the milk proteins to tangle into a solid mass, (curd, denature). The increased acidity (pH=4–5) also prevents the proliferation of other potentially pathogenic bacteria. To be named yoghurt, the product should at least contain the bacteria Streptococcus salivarius ssp thermophilus and Lactobacillus bulgaricus (official name Lactobacillus delbrueckii ssp. bulgaricus). Often these are co-cultured with other lactic acid bacteria for either taste or health effects (probiotics). These include L. acidophilus, Lactobacillus casei and Bifidobacterium'' species.
In most countries, a product may only be called yoghurt if there are live bacteria present in the final product. Pasteurized products (which have no living bacteria) are named fermented milk (drink).
In the US non-pasteurized yoghurt is sold as containing "live active culture" (or just as "live" ), which some believe to be nutritionally superior. In Spain, the yoghurt producers were divided among those who wanted to reserve the name yogurt for live yoghurt and those who wanted to include pasteurised yoghurt under that label (mostly the Pascual Hermanos group). Pasteurized yoghurt has a shelf life of months and does not require refrigeration. Both sides submitted scientific studies claiming differences or lack thereof between both varieties. Eventually the Spanish government allowed the label yogur pasteurizado instead of the former postre lácteo ("dairy dessert").
Because live yoghurt culture contains enzymes that break down lactose, some individuals who are otherwise lactose intolerant find that they can enjoy yoghurt without ill effects. Nutritionally, yoghurt is rich in protein as well as several B vitamins and essential minerals, and it is as low or high in fat as the milk it is made from.
Non-sweetened drinkable yoghurt is typically sold in the West under the name "(cultured) buttermilk." This term is a misnomer, as the drink has little in common with "true" buttermilk and is, in fact, most similar to kefir.
Yoghurt is often sold sweetened and flavored, or with added fruit on the bottom (sometimes referred to as fruit bottom), to offset its natural sourness. If the fruit is already stirred into the yoghurt, it is sometimes referred to as Swiss-style. Most yoghurt in the United States has pectin or gelatin added. Some specialty yoghurts have a layer of fermented fat at the top similar to cream cheese (e.g. brands like Brown Cow Yoghurt). Fruit jam is used instead of raw fruit pieces in the case of fruit yoghurts so that they can be stored for weeks.
Dahi yoghurt of the Indian subcontinent is known for its characteristic taste and consistency. The English term for yoghurt in India is curd.
Labneh yoghurt of Lebanon is a thickened yogurt that is used to make sandwiches by itself, or with olive oil, cucumber slices, olives, and various green herbs. It is also thickened further and rolled into balls that are preserved in olive oil, and fermented further for a few weeks before it is eaten. It is sometimes used with onions, meat, and nuts as a stuffing for a variety of Lebanese pies or Kebbeh كبة balls.
Bulgarian yoghurt is often strained by hanging in a cloth for a few hours to reduce water content. The resulting yoghurt is creamier, richer and milder in taste because of increased fat content. Hanging overnight is sometimes employed to make a concentrated yoghurt similar to cream cheese. Yoghurt is also used for preparation of Bulgarian milk salad. (Commercial versions of strained yoghurt are also made.)
A cold soup (called tarator in Bulgaria and cacık in Turkey) made of yoghurt is popular in Turkey and Bulgaria in the summertime. It is made from Ayran, cucumbers, garlic and ground walnuts.
Lassi is a yoghurt-based beverage, originally from India where two basic varieties are known: salty and sweet. Salty lassi is usually flavored with ground-roasted cumin and chile peppers; the sweet variety with rosewater and/or lemon, mango, or other fruit juice. Another yoghurt-based beverage, a salty drink called Ayran is quite popular in Turkey, Bulgaria and Greece. It is made by mixing yoghurt with water and adding salt. The same drink is known as tan in Armenia. A similar drink, Doogh, is popular in the Middle East between Lebanon and Iran; it differs from ayran by the addition of herbs (usually mint) and being carbonated (usually with seltzer water). In the United States, yoghurt-based beverages are often marketed under names like "Yogurt Smoothie" or "Drinkable Yogurt".
Kefir is a fermented milk drink originating in the Caucasus. A related Central Asian-Mongolian drink made from mare's milk is called kumis or, in Mongolia, airag. Some American dairies have offered a drink called "kefir" for many years (though lacking the carbonation and alcohol, and coming in fruit flavors), but began appearing (as of 2002) with names like "drinkable yoghurt" and "yoghurt smoothie".
Home-made yoghurt is consumed by many people throughout the world, and is the norm in countries where yoghurt has an important place in traditional cuisine, such as Bulgaria, Turkey, Greece* and India. Yoghurt can be made at home using a small amount of store-bought plain live active culture yoghurt as the starter culture. One very simple recipe starts with a litre of low-fat milk, but requires some means to incubate the fermenting yoghurt at a constant 43°C (109°F) for several hours. Yoghurt-making machines are available for this purpose. A run of the mill heating pad found in a pharmacy for muscle aches (set at medium), with a pot of tepid water on top to place the milk in, works fine. As with all fermentation processes, cleanliness is very important.
In Japan, Caspian Sea Yoghurt is a very popular home-made yoghurt. It is believed to have been introduced into the country by researchers in the form of a sample brought back from Georgia in the Caucasus region in 1986. This Georgian yogurt, called Matsoni which is mostly made up of Lactococcus lactis subsp. cremoris and Acetobacter orientalis[http://www.nih.go.jp/eiken/english/info/pdf/HNNews_no10.pdf has a unique viscous, honey-like texture and is milder in taste than many other yoghurts.
Caspian Sea yoghurt is particularly well suited for making at home because it does not require any special equipment and cultures at room temperature (20–30°C) in about 10 to 15 hours, depending on the temperature. * In Japan it is possible to buy a freeze-dried starter culture at big department stores or online, but many people obtain a quantity of the yoghurt from a friend and start making their own yoghurt from that.
Fermented foods | Dairy products | Desserts | Yoghurts
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