Yogurt is an ancient food that has gone by many names over the millennia: katyk (Armenia), dahi (India), zabadi (Egypt), mast (Iran), leben raib (Saudi Arabia), laban (Iraq and Lebanon), roba (Sudan), iogurte (Brazil), cuajada (Spain), coalhada (Portugal), dovga (Azerbaijan), and matsoni (Georgia, Russia, and Japan). It is believed that milk products were incorporated into the human diet around 10 000–5000 BC, with the domestication of milk-producing animals (cows, sheep, and goats, as well as yaks, horses, buffalo, and camels).2 However, milk spoiled easily, making it difficult to use. At that time, herdsmen in the Middle East carried milk in bags made of intestinal gut. It was discovered that contact with intestinal juices caused the milk to curdle and sour, preserving it and allowing for conservation of a dairy product for extended periods of time.
Indian Ayurvedic scripts, dating from about 6000 BC, refer to the health benefits of consuming fermented milk products. Today, there are more than 700 yogurt and cheese products found in Indian cuisine. For millennia, making yogurt was the only known safe method for preserving milk, other than drying it. Yogurt was well known in the Greek and Roman empires, and the Greeks were the first to mention it in written references in 100 BC, noting the use of yogurt by barbarous nations. In the Bible (Book of Job), Abraham owed his longevity and fecundity to yogurt consumption, and there is reference to the “Land of Milk and Honey,” which many historians have interpreted to be a reference to yogurt.
It is believed that the word “yogurt” comes from the Turkish word “yoğurmak,” which means to thicken, coagulate, or curdle.3 The use of yogurt by medieval Turks was recorded in the books Diwan Lughat al-Turk by Mahmud Kashgari and Kutadgu Bilig by K. H. Yusuf,7 both written in the 11th century. The texts mention the word “yogurt” and describe its use by nomadic Turks. The Turks were also the first to evaluate yogurt’s medicinal use for a variety of illnesses and symptoms, such as diarrhea and cramps, and to alleviate the discomfort of sunburned skin.
Genghis Khan, the founder of the Mongol Empire, is reputed to have fed his army yogurt, a staple of the Mongolian diet, based on the belief that it instilled bravery in his warriors. In 1542, King Francoise I of France introduced this dairy product to Western Europe after being offered yogurt as a treatment by the country’s Turkish allies for bouts of severe diarrhea. It was later mixed with a variety of ingredients, such as cinnamon, honey, fruits, and sweets, and was used as a dessert.
It was not until the 20th century that researchers provided an explanation for the health benefits associated with yogurt consumption. In 1905, a Bulgarian medical student, Stamen Grigorov, was the first to discover Bacillus bulgaricus (now L. bulgaricus), a lactic acid bacteria that is still used in yogurt cultures today. Based on Grigorov’s findings, in 1909, the Russian Nobel laureate, Yllia Metchnikoff, from the Pasteur Institute in Paris, suggested that lactobacilli in yogurt were associated with longevity in the Bulgarian peasant population. In the beginning of the 20th century, yogurt became known for its health benefits and was sold in pharmacies as a medicine. Yogurt found commercial success when Isaac Carasso, from Barcelona, began producing yogurt with jams. After fleeing the Nazi occupation, Daniel Carasso, Isaac Carasso’s son, founded Dannon (Danone in France). The first yogurt laboratory and factory were opened in France in 1932; in the United States, the first laboratory and factory were opened in 1941.
Yogurt is defined by the symbiosis of 2 strains of bacteria (S. thermophiles and L. bulgaricus) in a sterile environment at a very low temperature (36°C–42°C) for 3–8 h. Both bacterial strains must remain active in the final product (with at least 10 million bacteria/g, according to CODEX 2003).1 The process to which prepasteurized skimmed milk is submitted, before it is turned into yogurt, is responsible for changes in carbohydrates, proteins, and lipids. It yields an acidic flavor and a product with an improved appearance, taste, consistency, and digestibility. When milk lactose is used as the fermentation substrate, lactic acid and a series of other compounds are formed, contributing to its aroma. As a consequence of a decrease in pH, the development of undesirable microorganisms is delayed, the calcium and phosphorus present in milk are converted into their soluble form, and the majority of proteins, now calcium free, are better digested by proteolytic enzymes, which enhances its digestibility and overall bioavailability.
Other bacterial strains, such as Lactobacillus acidophilus and Bifidobacterium bifidus, are often added for potential health benefits. When yogurt is consumed daily, there may be diminished growth of pathogens, which is ultimately beneficial to the human gut.2 The protein content of some yogurts, such as Greek yogurt, is modified by concentrating or adding protein to provide twice the amount present in regular yogurt products. Calcium and vitamin D are also added to some products, adding nutritional value for populations with a high incidence of lactose intolerance or a low intake of dairy foods.
The types of yogurt consumed today are influenced by local traditions or correspond to certain lifestyles. In Eastern Europe and Asia, people consume milk that has undergone alcoholic fermentation by combining bacteria and yeasts (e.g., Kefir, Koumis); in Germany and Spain, yogurt is typically heat-treated to kill the bacteria; and in other countries, various probiotics and/or prebiotics are added to the mix.