Fermented dairy products are associated with improved health outcomes. Fermented food are utilizing from centuries as the method of food preservation. Research says that fermented milk products reduced the risk of gastrointestinal, cardiovascular, and many other diseases. Fermented food defined as Fermented food manufactured through controlled microbial growth of major and minor food components. Fermented (or cultured) milks are prepared by inoculating appropriate bacteria into usually heat-treated animal milk, then incubating to lower the pH, with or without coagulation pretreatment. Dahi is the one of the most nutritive dairy product which is produced by bacterial fermentation of milk. It is a nutritiously balanced food containing almost all the nutrients present in milk but in a more assailable form. Dahi is considered as oldest Indian fermented milk product. Dahi is used as most nutritive meal in today’s house hold. People in India prepare dahi at home for using in daily basis meal.
Streptococcus lactis, Streptococcus cremoris, Streptococcus diacetylactis, Lactobacillus such as Lactobacillus bulgaricus, Lactobacillus acidophilus, and L. casei & Streptococcus thermophiles are some of the culture used in large scale production of dahi. Due to their increased acid resistance, lactobacilli dominate in sour dahi, whereas streptococci dominate in sweet dahi.
Yogurt is often milk that has been fermented and acidified with viable and well-defined bacteria, resulting in a thicker, often flavoured product with a long shelf life. It is a vehicle for fortification and contains vital nutrients (added probiotics, fibers, vita-mines, and minerals). It’s also easy to change the consistency and aroma by adding sweeteners, fruits, and flavour. The word yogurt is believed to be derived from the Turkish word “yoğurmak,” which means to thicken, coagulate, or curdle.
Mostly cow milk uses for the making of yogurt. Lactobacillus bulgaricus and Streptococcus thermophilus are the two main culture used in yogurt production. Yogurt is prepared by combining heated milk with bacteria, specifically Lactobacillus bulgaricus and Streptococcus thermophilus, and allowing it to sit at a warm temperature (110-115°F) for many hours. Lactobacilli and bifidobacteria of different types can be added. The bacteria convert the sugar in milk, called lactose, to lactic acid, which thickens the milk and develops its distinctive tart flavor.