Yoghurt: A Fermented Dairy Product

Yoghurt is a dairy product produced by the fermentation of milk carried by the activity of bacteria. The bacteria used for the production of yoghurt are represented by the term yoghurt cultures. These bacteria ferment the milk sugar lactose into lactic acid which then acts on the milk protein to give yoghurt its texture and characteristic flavor. Basically cow's milk is used for making yoghurt all over the world but milk from water buffalo, goats, sheep, camels and yaks is also used for the same purpose in different parts of the world. In theoretical terms milk from any mammal can be used for making yoghurt. Soy-yoghurt is a non-dairy product obtained from the soy milk derived from soybeans.

Dairy yoghurt is actually produced by the culture of Lactobacillus delbrueckii subsp. bulgaricus and Streptococcus salivarius subsp. thermophilus bacteria. Sometimes the species of Lactobacillus acidophilus, Lactobacillus bifidus and Lactobacillus casei are also used for culturing. For making yoghurt first the milk is heated at 80°C to kill any undesirable bacteria if present and setting of milk proteins. The hot milk is then allowed to cool at 45°C. When the milk is completely cool then bacterial culture is added and the mixture is allowed to undergo fermentation for about 7-8 hours. The word yoghurt has been derived from a Turkish word meaning to thicken or coagulate. Literature suggests that the used of cultured milk products began about 2000 years ago. The early yoghurt was fermented spontaneously and kept in a goatskin bag that was used for transportation. In 1880's men used yoghurt for cleaning their goats and sheep. Many women of the olden times also used yoghurt for cleaning their bodies as well as hairs. It was the best cleaning agent known at that time.

Yoghurt carries a very good nutritional value. It is a rich source of protein, calcium, riboflavin, vitamin B6 and vitamin B12. People who are lactose-intolerant can easily digest it as the milk sugar has been converted into lactic acid by the combined action of the bacteria. Sometimes it is also used to treat the antibiotic-associated diarrhea. A study published in the International Journal of Obesity focused that consumption of low-fat yoghurt helps in weight loss. Dadih is western Sumatran yoghurt prepared from the milk of water buffalo and the fermentation is carried out in the bamboo tubes. It is very popular in Nepal and is served as an appetizer as well as a dessert. In Tibet yak milk is actually used for the same purpose and consumed by people. Cream-top variety is actually made from the unhomogenized milk. Raita is a very popular Indian condiment often used as a side dish.