Yogurt is milk, which has been fermented using bacteria referred to as yogurt cultures. When yogurt cultures ferment the lactose in milk, it produces lactic acid which works on milk protein resulting in a characteristic tart flavor and texture that separate yogurt from other dairy products.
Although most yogurt available globally is made using cow milk, yogurt can also be made using milk from goats, buffalos, camels, yaks, ewes, and mares. The milk may or may not be homogenized or pasteurized.
The process of making yogurt, as well as the milk used makes
it possible to have different types of yogurt.
Some countries have regulations governing the number of bacteria (colony-forming units of bacteria) that should be contained in yogurt. In China, for instance, yogurt should have 1 million CFU+ of lactobacillus bacteria per milliliter.
To make yogurt, the milk must be heated to approximately 185 F or 85 C. Heating is necessary for denaturing milk proteins and prevent them from forming curds. The milk is then cooled to about 113 F or 45 C before the yogurt culture is added. The temperature is maintained for 4 -12 hours to enable fermentation. The resulting yogurt is usually sweetened and flavored to remove its natural sourness.