Yogurt starter can be divided into three types according to different physical forms: liquid yoghourt starter, frozen yoghourt starter and direct-throw yoghourt starter. The commercially available yogurt starter belongs to the direct-throw yogurt starter. The product quality of direct-throw yogurt starter is uniform, its activity can be determined in advance, the inoculation amount can be accurately controlled, and it is easy to mix evenly, so the quality of starter and yogurt can be guaranteed to be stable.

Yogurt starter mainly contains the basic fermentation bacteria Bulgaria and Streptococcus hygrophyticus. Milk is used as the substrate of anaerobic fermentation (the main fermentation product is lactic acid). Some nutrients in yogurt fermented by lactic acid are more easily absorbed by human body than fresh milk. Some yogurt starters contain more probiotics, such as Bifidobacterium nucleolus yogurt starter, which contains six kinds of natural probiotics. In addition to Bulgaria and Streptococcus hygrophyticus, there are also Bifidobacterium lactis, Lactobacillus acidophilus, Lactobacillus casei and Lactobacillus rhamnosus, which are the most probiotic yogurt starter powders on the market at present.