Yogurt

Yogurt (UK: ; US: ; 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 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 (CXS 243-2003). 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.