Yoghurt



Yoghurt or yogurt, or less commonly yoghourt or yogourt (see spelling below), is a dairy product produced by bacterial fermentation of milk. Fermentation of the milk sugar (lactose) produces lactic acid, which acts on milk protein to give yoghurt its texture and its characteristic tang. Yoghurt substitutes can be made from soya milk.

History
There is evidence of cultured milk products being produced as food for at least 4,500 years. The earliest yoghurts were probably spontaneously fermented by wild bacteria living on the goat skin bags carried by the Bulgars (or Hunno-Bulgars), a nomadic people who began migrating into Europe in the second century AD and eventually settled in the Balkans at the end of the seventh century. Today, many different countries claim yoghurt as their own, yet there is no clear evidence as to where it was first discovered.

The use of yoghurt by ancient Turks is recorded in the books Diwan Lughat al-Turk by Mahmud Kashgari and Kutadgu Bilig by Yusuf Has Hajib written in the eleventh century. In both texts the word "yoghurt" is mentioned in different sections and its use by nomadic Turks is described. The first account of a European encounter with yoghurt occurs in French clinical history: Francis I suffered from a severe diarrhoea which no French doctor could cure. His ally Suleiman the Magnificent sent a doctor, who allegedly cured the patient with yoghurt.

Until the 1900s, yoghurt was a staple in diets of the South Asian, Central Asian, Western Asian, South Eastern European and Central European regions. The Russian biologist Ilya Ilyich Mechnikov had an unproven hypothesis that regular consumption of yoghurt was responsible for the unusually long lifespans of Bulgarian peasants. Believing Lactobacillus to be essential for good health, Mechnikov worked to popularise yoghurt as a foodstuff throughout Europe. It fell to a Sephardic Jewish entrepreneur named Isaac Carasso to industrialise the production of yoghurt. In 1919, Carasso, who was from Salonika, started a small yoghurt business in Barcelona and named the business Danone ("little Daniel") after his son. Carasso emigrated to the United States during World War II and set up a business in New York City under an Americanised version of the name: Dannon.

Yoghurt with added fruit jam was invented to protect yoghurt from decay. It was patented in 1933 by the Radlická Mlékárna dairy in Prague, and introduced to the United States in 1947, by Dannon.

Culture
Yoghurt is made by introducing specific bacteria strains into milk, which is subsequently fermented under controlled temperatures and environmental conditions (inside a bioreactor), especially in industrial production. The bacteria ingest natural milk sugars and release lactic acid as a waste product. The increased acidity causes milk proteins to tangle into a solid mass (curd in a process called denaturation). The increased acidity (pH=4–5) also prevents the proliferation of potentially pathogenic bacteria. In the U.S., to be named yoghurt, the product must contain the bacteria strains Streptococcus salivarius subsp. thermophilus and Lactobacillus delbrueckii subsp. bulgaricus. Often these two are co-cultured with other lactic acid bacteria for taste or health effects (See probiotics). These include L. acidophilus, Lactobacillus casei and Bifidobacterium species.

In most countries, a product may be called yoghurt only if live bacteria are present in the final product. In the U.S., non-pasteurised yoghurt can be marketed as "live" or containing "live active culture". A small amount of live yoghurt can be used to inoculate a new batch of yoghurt, as the bacteria reproduce and multiply during fermentation. Pasteurised products, which have no living bacteria, are called fermented milk (drink). In Spain, yoghurt producers were divided between those who wanted to reserve the name yoghurt for live yoghurt and those who wanted to include pasteurised products, the Pascual Hermanos group being the most prominent among the latter. Pasteurised yoghurt has a shelf life of months and does not require refrigeration. Both sides submitted scientific studies supporting their claims. The Spanish government eventually allowed the label yogur pasteurizado to replace the former postre lácteo ("dairy dessert").

Non-sweetened, drinkable yoghurt is sometimes sold in the West as buttermilk or cultured buttermilk. This is a misnomer, as the drink has little in common with buttermilk and is, in fact, most similar to kefir.

Yoghurt has nutritional benefits beyond those of milk: people who are lactose-intolerant often enjoy yoghurt without ill effects, apparently because live yoghurt cultures contain enzymes which help break down lactose inside the intestine.

Yoghurt also has medical uses, in particular for a variety of gastrointestinal conditions, and in preventing antibiotic-associated diarrhea. One study suggests that eating yoghurt containing L. acidophilus helps prevent vulvovaginal candidiasis, though the evidence is not conclusive.

Presentation
To offset its natural sourness, yoghurt can be sold sweetened, flavoured, or in containers with fruit or fruit jam on the bottom. If the fruit has been stirred into the yoghurt before purchase, it is commonly referred to as Swiss-style. Most yoghurts in the United States have added pectin or gelatine. Like cream cheese, some specialty yoghurts have a layer of fermented fat at the top. Fruit jam is used instead of raw fruit pieces in fruit yoghurts to allow storage for weeks. "Strained" yoghurt is the concentrated residue (described as a sort of "yoghurt cheese") produced by filtering plain yoghurt that is without flavourings, gelatine, pectin, or other additives through a paper or cloth filter, and allowing water and whey to drain from away.

Varieties

 * Strained yoghurts, which include Greek Yoghurt, Dahi and Bulgarian Yoghurt are types of yoghurt which are strained through a cloth or paper filter, traditionally made of muslin, to remove the whey, giving a much thicker consistency, and a distinctive, slightly sour, taste. Some types are boiled in open vats first, so that the liquid content is reduced.


 * Dadiah, or Dadih, is a traditional West Sumatran yoghurt made from water buffalo milk. It is fermented in bamboo tubes.


 * Labneh yoghurt of Lebanon is a thickened yoghurt used for sandwiches. Olive oil, cucumber slices, olives, and various green herbs may be added. It can be thickened further and rolled into balls, preserved in olive oil, and fermented for a few more weeks. It is sometimes used with onions, meat, and nuts as a stuffing for a variety of Lebanese pies or Kebbeh ( كبة ) balls.


 * Tarator/cacık is a popular cold soup made from yoghurt, popular during summertime in Bulgaria, Macedonia, and Turkey. It is made with Ayran, cucumbers, and optionally garlic and ground walnuts in Bulgaria, and generally without walnuts in Turkey.


 * Rahmjoghurt is a creamy yoghurt with much higher milkfat content (10%) than most yoghurts offered in English-speaking countries, is available in Germany and other countries.

Drinks

 * Lassi is a yoghurt-based beverage originally from the Indian subcontinent that is usually slightly salty or sweet. Salty lassi is usually flavored with ground, roasted cumin and chile peppers. The sweet variety is flavoured with rosewater, lemon, mango or other fruit juice. Another yoghurt-based beverage, a salty drink called ayran, is popular in Azerbaijan, Turkey, Bulgaria, Macedonia, Kazakhstan and Kyrgyzstan. It is made by mixing yoghurt with water and adding salt. The same drink is known as tan in Armenia, "Laban Ayran" in Syria, "Shenina" in Jordan, "Moru" in South India, and "Laban Arbil" in Iraq. 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 is carbonated, usually with seltzer water. In the United States, yoghurt-based beverages are often marketed under names like "yoghurt smoothie" or "drinkable yoghurt". They are also popular in Ecuador where the primary form of yoghurt is "bebida de yogurt", which literally means drink of yoghurt.


 * Yop is popular in Canada and the UK.


 * Kefir is a fermented milk drink originating in the Caucasus. A related Central Asian-Turco Mongolian drink made from mare's milk is called kumis, or airag in Mongolia. Some American dairies have offered a drink called "kefir" for many years with fruit flavours but without carbonation or alcohol. As of 2002, names like "drinkable yoghurt" and "yoghurt smoothie" have been introduced.

Homemade
Yoghurt is customarily made in domestic environments in regions where yoghurt has an important place in traditional cuisine. It can be made from a small amount of store-bought, plain, live culture yoghurt by adding milk and heating at a constant, but not boiling, temperature. Special yoghurt-making machines assist in small-batch yoghurt-making.

Caspian Sea Yoghurt is believed to have been introduced into Japan in 1986 by researchers returning from a trip to the Caucasus region in Georgia. This variety, called Matsoni, is started with Lactococcus lactis subsp. cremoris and Acetobacter orientalis species and has a unique, viscous, honey-like texture. It is milder in taste than other varieties of yoghurts. Ideally, Caspian Sea yoghurt is made at home because it requires no special equipment nor unobtainable culture. It can be made at room temperature (20–30°C) in 10 to 15 hours. In Japan, freeze-dried starter cultures are sold in department stores and online, although many people obtain starter cultures from friends.

Etymology and spelling
The word "yoghurt" comes from the Turkish yoğurt. The word is derived from the adjective yoğun, which means "dense" and "thick", or from the verb yoğurmak, meaning "to knead". Originally, the verb may have meant "to make dense", which is how yoghurt is made. The letter ğ was traditionally rendered as "gh" in transliterations of Turkish, which used to be written in a variant of the Arabic alphabet until the introduction of the Latin alphabet in 1928. In older Turkish the letter denoted a voiced velar fricative, but this sound is elided between back vowels in modern Turkish, in which the word is pronounced as. Some eastern dialects retain the consonant in this position, and Turks in the Balkans pronounce the word with a hard.

In English, there are several variations of the spelling of the word. In the United States, yogurt is the usual spelling and yoghurt a minor variant. In the United Kingdom, yoghurt and yogurt are both current, yoghurt being more common, and yoghourt is an uncommon alternative. Canada uses mostly yogurt and yogourt; in Australia and New Zealand yoghurt prevails.

Whatever the spelling, the word is pronounced with either a short "o" or a long "o" in Britain, and with a long "o" in North America, Ireland and Australia (IPA: UK or ; North America ; Australia ).