Kefir vs Yogurt
i want to simply know the difference. i mean, i know the difference in mouthfeel, flavor, etc cuz i eat both of them quite frequently. what i am asking about here is what actually is going on bacterially (i guess) that makes these two seemingly similar products different. thanks guys.
Yogurt is made with thermophyllic bacteria that thrive in warm temperatures. Milk of any type (I use powdered because it is fat free and cheap) is innoculated with a yogurt starter. The milk is heated to and kept at about 115 degreed Fahrenheit for 5 to 24 hours. The bacteria consume some or all of the lactose in the milk and produce lactic acid. This acid causes the milk proteins to denature and coagulate which forms the delightful, custard-like, gel that is yogurt. Any yogurt with live cultures can be used as a starter for the next batch indefinitely.
Kefir is different. Milk is innoculated with mesophyllic bacteria that thrive in room temperatures as well as lactose consuming yeasts. The kefir incubates at room temperature in a sealed container. As it ferments some yeast can collect at the surface so it needs to be occasionally shaken. The bacteria and yeast form gelatinous structures that are called "grains". These are the mother culture and can be used indefinitely to start new batches of kefir. The yeast in the kefir consume lactose and produce CO2 and alcohol. Because of this, kefir can range from .5% to 1.5% alcohol and has a characteristic delightful effervescence. Unlike yogurt, prepared kefir cannot be used indefinitely to produce more kefir- you have to have the grains.
Have a nice day.