YUGURT

YOGURT

Yogurt or yoghurt is a dairy product produced by bacterial fermentation of milk. The bacteria used to make yogurt are known as "yogurt cultures". Fermentation of lactose by these bacteria produces lactic acid, which will act on milk protein to give yogurt its texture and its characteristic tang.

Worldwide, cow's milk is most commonly used to make yogurt, but milk from water buffalo, goats, sheep, horses, camels, and yaks is also used in various parts of the world.

Dairy yogurt is produced using a culture of Lactobacillus delbrueckii subsp. bulgaricus and Streptococcus salivarius subsp. thermophilus bacteria. In addition, other lactobacilli and bifidobacteria are also sometimes added during or after culturing yogurt.

The milk is first heated to about 80 °C (176 °F) to kill any undesirable bacteria and to denature the milk proteins so that they set together rather than form curds. The milk is then cooled to about 45 °C (112 °F). The bacteria culture is added, and the temperature is maintained for 4 to 7 hours to allow fermentation. After that, yogurt would be ready for consumption.

How milk was first cultured into yogurt remains a mystery. Actually, analyses of the L. delbrueckii subsp. bulgaricus genome indicated that the bacteria may have originated on the surface of a plant. Maybe milk became spontaneously and unintentionally infected through contact with plants, or perhaps bacteria were transferred via the udder of domestic milk-producing animals.