Yoghurt

Yogurt (; , from tr, yoğurt, also spelled yoghurt, yogourt or yoghourt) 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.

Yogurt is produced using a culture of ''Lactobacillus delbrueckii'' subsp. ''bulgaricus'' and ''Streptococcus thermophilus'' bacteria. In addition, other lactobacilli and bifidobacteria are sometimes added during or after culturing yogurt. Some countries require yogurt to contain a specific amount of colony-forming units (CFU) of bacteria; in China, for example, the requirement for the number of lactobacillus bacteria is at least 1 million CFU per milliliter.

To produce yogurt, milk is first heated, usually to about 85 °C (185 °F), to denature the milk proteins so that they do not form curds. After heating, the milk is allowed to cool to about 45 °C (113 °F). The bacterial culture is mixed in, and a warm temperature of 30–45 °C (86–113 °F) is maintained for 4 to 12 hours to allow fermentation to occur, with the higher temperatures working faster but risking a lumpy texture or whey separation.

Etymology and spelling

The word is derived from tr, yoğurt, and is usually related to the verb , "to knead", or "to be curdled or coagulated; to thicken". It may be related to , meaning thick or dense. The sound ğ was traditionally rendered as "gh" in transliterations of Turkish from around 1615–1625.

In English, spelling variations include ''yogurt'', ''yoghurt'', and to a lesser extent ''yoghourt'' or ''yogourt''. In the United Kingdom, the word is usually spelled ''yoghurt'' while in the United States the spelling is ''yogurt''. In Australia, New Zealand and South Africa, both spellings are commonly found. Canada has its own spelling, ''yogourt'', a minority variant of the French , although ''yogurt'' and ''yoghurt'' are also used.

History

Analysis of the ''L. delbrueckii'' subsp. ''bulgaricus'' genome indicates that the bacterium may have originated on the surface of a plant. Milk may have become spontaneously and unintentionally exposed to it through contact with plants, or bacteria may have been transferred from the udder of domestic milk-producing animals. The origins of yogurt are unknown, but it was probably invented by Neolithic people in Central Asia and Mesopotamia around 5000 BC, when the first milk-producing animals were domesticated. They most likely found out how to ferment milk by chance and in all likelihood, yogurt was discovered independently in this way in many different places at different times.

The cuisine of ancient Greece included a dairy product known as oxygala () which was a form of yogurt. Galen (AD 129 – c. 200/c. 216) mentioned that oxygala was consumed with honey, similar to the way thickened Greek yogurt is eaten today. The oldest writings mentioning yogurt are attributed to Pliny the Elder, who remarked that certain "barbarous nations" knew how "to thicken the milk into a substance with an agreeable acidity". The use of yogurt by medieval Turks is recorded in the books ''Dīwān Lughāt al-Turk'' by Mahmud Kashgari and ''Kutadgu Bilig'' by Yusuf Has Hajib written in the 11th century. Both texts mention the word "yogurt" in different sections and describe its use by nomadic Turks. The earliest yogurts were probably spontaneously fermented by wild bacteria in goat skin bags.

Some accounts suggest that Mughal Indian emperor Akbar's cooks would flavor yogurt with mustard seeds and cinnamon. Another early account of a European encounter with yogurt occurs in French clinical history: Francis I suffered from a severe diarrhea which no French doctor could cure. His ally Suleiman the Magnificent sent a doctor, who allegedly cured the patient with yogurt. Being grateful, the French king spread around the information about the food that had cured him.

Until the 1900s, yogurt was a staple in diets of people in the Russian Empire (and especially Central Asia and the Caucasus), Western Asia, South Eastern Europe/Balkans, Central Europe, and the Indian subcontinent. Stamen Grigorov (1878–1945), a Bulgarian student of medicine in Geneva, first examined the microflora of the Bulgarian yogurt. In 1905, he described it as consisting of a spherical and a rod-like lactic acid-producing bacteria. In 1907, the rod-like bacterium was called ''Bacillus bulgaricus'' (now ''Lactobacillus delbrueckii'' subsp. ''bulgaricus''). The Russian biologist and Nobel laureate Ilya Mechnikov, from the Institut Pasteur in Paris, was influenced by Grigorov's work and hypothesized that regular consumption of yogurt was responsible for the unusually long lifespans of Bulgarian peasants. Believing ''Lactobacillus'' to be essential for good health, Mechnikov worked to popularize yogurt as a foodstuff throughout Europe.

Isaac Carasso industrialized the production of yogurt. In 1919, Carasso, who was from Ottoman Salonika, started a small yogurt business in Barcelona, Spain, and named the business Danone ("little Daniel") after his son. The brand later expanded to the United States under an Americanized version of the name: Dannon. Yogurt with added fruit jam was patented in 1933 by the Radlická Mlékárna dairy in Prague.

Yogurt was introduced to the United States in the first decade of the twentieth century, influenced by Élie Metchnikoff's ''The Prolongation of Life; Optimistic Studies'' (1908); it was available in tablet form for those with digestive intolerance and for home culturing. It was popularized by John Harvey Kellogg at the Battle Creek Sanitarium, where it was used both orally and in enemas, and later by Armenian immigrants Sarkis and Rose Colombosian, who started "Colombo and Sons Creamery" in Andover, Massachusetts, in 1929.

Colombo Yogurt was originally delivered around New England in a horse-drawn wagon inscribed with the Armenian word " madzoon" which was later changed to "yogurt", the Turkish language name of the product, as Turkish was the lingua franca between immigrants of the various Near Eastern ethnicities who were the main consumers at that time. Yogurt's popularity in the United States was enhanced in the 1950s and 1960s, when it was presented as a health food by scientists like Hungarian-born bacteriologist Stephen A. Gaymont. Plain yogurt still proved too sour for the American palate and in 1966 Colombo Yogurt sweetened the yogurt and added fruit preserves, creating "fruit on the bottom" style yogurt. This was successful and company sales soon exceeded $1 million per year. By the late 20th century, yogurt had become a common American food item and Colombo Yogurt was sold in 1993 to General Mills, which discontinued the brand in 2010.

Market and consumption

In 2017, the average American ate of yogurt. The average consumption of yogurt has been declining since 2014.

Sale of yogurt was down 3.4 percent over the 12 months ending in February 2019. The decline of Greek-style yogurt has allowed Icelandic skyr to gain a foothold in the United States with sales of the latter increasing 24 percent in 2018 to $173 million.

Nutrition

Yogurt (plain yogurt from whole milk) is 81% water, 9% protein, 5% fat, and 4% carbohydrates, including 4% sugars (table). A 100-gram amount provides of dietary energy. As a proportion of the Daily Value (DV), a serving of yogurt is a rich source of vitamin B₁₂ (31% DV) and riboflavin (23% DV), with moderate content of protein, phosphorus, and selenium (14 to 19% DV; table).

Tilde (~) represents missing or incomplete data.
The above shows little difference exists between whole milk and yogurt made from whole milk with respect to the listed nutritional constituents.

Health research

Because it may contain live cultures, yogurt is often associated with probiotics, which have been postulated as having positive effects on immune, cardiovascular or metabolic health.

As of the early 21st century, high-quality clinical evidence was insufficient to conclude that consuming yogurt lowers the risk of diseases or otherwise improves health. Meta-analyses found that consuming 80 grams per day of low-fat yogurt was associated with a lower risk of developing type 2 diabetes and a lower incidence of hip fracture in post-menopausal women. A 2021 review found a cause-and-effect relationship between yogurt consumption and improved lactose tolerance and digestion, and that potential associations exist between yogurt consumption and improving bone health, as well as lowering the risk of some diseases, including cancers and metabolic syndrome.

Safety

Yogurt made with raw milk can be contaminated with bacteria that can cause significant illness and death, including ''Listeria'', ''Cryptosporidium'', ''Campylobacter'', '' Brucella'', ''Escherichia coli'' and ''Salmonella''. Yogurts can also be contaminated with aflatoxin-producing ''Aspergillus flavus'', ''Aspergillus parasiticus'' and '' Aspergillus nomius''.

Contamination occurs in traditionally prepared yogurts more often than industrially processed ones, but may affect the latter as well if manufacturing and packaging practices are suboptimal.

When mold forms on yogurt it can not be scraped away. The consistency of yogurt allows the mold to penetrate deeply under the surface where it spreads.

Varieties and presentation

'' Dahi'' is a yogurt from the Indian subcontinent, known for its characteristic taste and consistency. The word ''dahi'' seems to be derived from the Sanskrit word ''dadhi'' ("sour milk"), one of the five elixirs, or panchamrita, often used in Hindu ritual. Sweetened dahi (''mishti doi'' or ''meethi dahi'') is common in eastern parts of India, made by fermenting sweetened milk. While cow's milk is currently the primary ingredient for yogurt, goat and buffalo milk were widely used in the past, and valued for the fat content (see buffalo curd).

Dadiah or dadih is a traditional West Sumatran yogurt made from water buffalo milk, fermented in bamboo tubes. Yogurt is common in Nepal, where it is served as both an appetizer and dessert. Locally called ''dahi'', it is a part of the Nepali culture, used in local festivals, marriage ceremonies, parties, religious occasions, family gatherings, and so on. One Nepalese yogurt is called '' juju dhau'', originating from the city of Bhaktapur. In Tibet, yak milk (technically dri milk, as the word yak refers to the male animal) is made into yogurt (and butter and cheese) and consumed.

In Northern Iran, ''Mâst Chekide'' is a variety of kefir yogurt with a distinct sour taste. It is usually mixed with a pesto-like water and fresh herb purée called delal. Common appetizers are spinach or eggplant borani, ''Mâst-o-Khiâr'' with cucumber, spring onions and herbs, and ''Mâst-Musir'' with wild shallots. In the summertime, yogurt and ice cubes are mixed together with cucumbers, raisins, salt, pepper and onions and topped with some croutons made of Persian traditional bread and served as a cold soup. Ashe-Mâst is a warm yogurt soup with fresh herbs, spinach and lentils. Even the leftover water extracted when straining yogurt is cooked to make a sour cream sauce called kashk, which is usually used as a topping on soups and stews.

Matsoni is a Georgian yogurt in the Caucasus and Russia. Tarator and are cold soups made from yogurt during summertime in eastern Europe. They are made with ayran, cucumber