Fermented milk refers to a large class of dairy products made from animal milk such as milk by lactic acid bacteria fermentation process, mainly including yogurt, active milk, cheese, acid cream, etc. Fermented milk containing a large number of beneficial active bacteria is one of the ideal foods for modern human beings with both nutrition and health care functions.

Fermented milk is an acidic curd-like product fermented by milk and dairy products under the action of characteristic bacteria. The characteristic bacteria of this kind of products must exist in large quantities during the shelf life, which can continue to survive and have activity. Therefore, fermented milk refers to a curd-like product made by adding lactic acid bacteria, also known as Lactobacillus bulgaricus and Streptococcus thermophilus, and the finished product must contain a large number of corresponding active microorganisms.