Yogurt

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.
Yogurt is produced using a culture of Lactobacillus delbrueckii subsp. bulgaricus and Streptococcus thermophilus bacteria. 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 of bacteria; for example, in China the requirement for the number of lactobacillus bacteria is at least 1 million CFU per milliliter. Some countries also regulate which bacteria can be used: for example, in France, a product can only be labeled as "yaourt" or "yoghourt" if it has been fermented exclusively by Lactobacillus delbrueckii subsp. bulgaricus and Streptococcus thermophilus, a requirement that aligns with the international definition of yogurt in the Codex Alimentarius on fermented milk.
The bacterial culture is mixed in, and a warm temperature of 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 for yogurt is derived from the, and is usually related to the verb yoğurmak, "to knead", or "to be curdled or coagulated; to thicken". It may be related to yoğun, meaning thick or dense. The sounds historically represented by the Arabic letter ghayn in the Turkish language ranging from a voiced velar fricative to a voiced velar plosive were traditionally romanized as "gh" prior to the introduction of a new Latin-based Turkish alphabet and the letter "ğ" in 1929, thus "yoghurt" spelled with a "gh" is first attested in sources from 1615 to 1625.
In English, spelling variations include yogurt, yoghurt, and to a lesser extent yoghourt or yogourt. In the United Kingdom, Australia, New Zealand and South Africa the word is usually spelled yoghurt, while in the United States the spelling is yogurt. Canada has its own spelling, yogourt, a minority variant of the French yaourt, 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 discovered first 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 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.
Until the 1900s, yogurt was a staple in diets of people in the Russian Empire, Western Asia, South Eastern Europe/Balkans, Central Europe, and the Indian subcontinent. Stamen Grigorov, 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. 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.
Industrialization of yogurt production is credited to Isaac Carasso, who, in 1919, started a small yogurt business in Barcelona, Spain, naming the business Danone 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 ; 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.

Nutrition

Yogurt is 81% water, 9% protein, 5% fat, and 4% carbohydrates, including 4% sugars. A 100-gram amount provides of dietary energy. As a proportion of the Daily Value, a serving of yogurt is a rich source of vitamin B₁₂ and riboflavin, with moderate content of protein, phosphorus, and selenium.

Property	Milk	Yogurt
Energy
Total carbohydrates	12.8 g	12 g
Total fat	7.9 g	8.5 g
Cholesterol	24 mg	32 mg
Protein	7.9 g	9 g
Calcium	276 mg	296 mg
Phosphorus	222 mg	233 mg
Potassium	349 mg	380 mg
Sodium	98 mg	113 mg
Vitamin A	249 IU	243 IU
Vitamin C	0.0 mg	1.2 mg
Vitamin D	96.5 IU	~
Vitamin E	0.1 mg	0.1 mg
Vitamin K	0.5 μg	0.5 μg
Thiamine	0.1 mg	0.1 mg
Riboflavin	0.3 mg	0.3 mg
Niacin	0.3 mg	0.2 mg
Vitamin B6	0.1 mg	0.1 mg
Folate	12.2 μg	17.2 μg
Vitamin B12	1.1 μg	0.9 μg
Choline	34.9 mg	37.2 mg
Betaine	1.5 mg	~
Water	215 g	215 g
Ash	1.7 g	1.8 g

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.
A 2011 review stated that 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. Daily intake of 50 grams of yogurt has been shown to reduce risk of overweight or obesity by 13%, and reduce risk of type 2 diabetes by 7%. Yogurt consumption has been associated with reduced risk of cardiovascular disease, and insulin resistance. Some of the benefits were somewhat better for the lower fat yogurts. Many commercial yogurt products are supplemented with extra probiotic bacteria.

Safety

Yogurt made with raw milk can be contaminated with bacteria that can cause significant illness and even result in 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.