Yogurt (; ; also spelled yoghurt, yogourt or yoghourt) is a food produced by bacterial fermentation of milk. The bacteria ferment the sugars in the milk and produce lactic acid, which acts on milk protein to give yogurt its texture and characteristic tart flavor. Yogurt is most commonly made from cow's milk, but milk from water buffalo, goats, ewes, mares, camels, and yaks can also be used.
The main bacteria used to produce yogurt are Lactobacillus delbrueckii subsp. bulgaricus and Streptococcus thermophilus. 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; 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 or 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 on fermented milk (CXS 243-2003).
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 The word, yogurt (also yoghurt with variations), is derived from Ottoman Turkish for yugurt or yoğurt, having its root yog meaning "to condense" as related to yogur (to "knead"). It was first used in English in 1625.
History Genome sequencing of Lactobacillus delbrueckii subsp. bulgaricus shows that the lactic acid bacteria adapted from a plant-associated habitat into the lactose-rich and stable protein milk environment through the loss of superfluous functions and protocooperation with Streptococcus thermophilus. The two bacteria used for modern yogurt production may have originated from plants in Bulgaria, where viable, fermenting strains of L. d. bulgaricus and S. thermophilus have been cultivated from plant samples.
Yogurt containing L. d. bulgaricus and S. thermophilus was first identified by the Bulgarian physician and microbiologist Stamen Grigorov in 1905. Grigorov experimented with samples of home-made Bulgarian yogurt or soured milk which he had brought from his native village, notably describing Bacille A., later named Bacillus bulgaricus and now known as Lactobacillus delbrueckii subsp. bulgaricus, as a small rod-shaped bacterium that caused milk to curdle and turn into yoghurt. The preparation of fermented milk products in the Balkan Peninsula existed by the 7th century AD, where a form of yogurt called katuk was prepared by the Bulgars, a historical Turkic tribe.
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 (AD 129 – /) 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 Natural History of Pliny, tr. John Bostock, Henry Thomas Riley, London: Bell, 1856–93, Volume 3 (book 11, section 239), p. 84: "It is a remarkable circumstance, that the barbarous nations which subsist on milk have been for so many ages either ignorant of the merits of cheese, or else have totally disregarded it; and yet they understand how to thicken milk and form therefrom an acrid kind of milk with a pleasant flavor, as well as a rich butter". 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 (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.
Industrialization of yogurt production is credited to Isaac Carasso, who, in 1919, started a small yogurt business in Barcelona, Spain, naming 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 the Colombo and Sons Creamery in Andover, Massachusetts, in 1929.
Colombo yogurt was reportedly first delivered around New England in a horse-drawn wagon bearing the Armenian word "madzoon"; this was later replaced with "yogurt", a term that was more familiar to many of the company's customers from the eastern Mediterranean and Near East. 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
Plain yogurt from whole milk 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 (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).
+ Comparison of whole milk and plain yogurt from whole milk, one cup (245 g) each 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. There is little difference 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, scraping it off does not eliminate it, as yogurt's consistency allows the mold to penetrate and spread deeply under the surface.
Varieties and presentation
Various techniques for fermenting milk into yogurts exist across countries and local regions.
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).
Bogurar doi is a traditional sweetened yogurt originating from Bogura, Bangladesh. It is a widely-consumed regional dairy product, forming part of Bangladeshi culinary heritage. It has formal recognition as a geographical indication product in Bangladesh.
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.