1) Lactobacillus acidophilus (Lactobacillusacidophilus): Lactobacillus acidophilus is a common probiotic that can play an important role in the fermentation process of yogurt. It can convert lactose to lactic acid, reduce the pH of yogurt, and produce a special flavor and taste.

2) Lactobacillus bulgaricus (Lactobacillusbulgaricus): Lactobacillus bulgaricus is another common probiotic in yogurt. It also has the ability to convert lactose into lactic acid. Lactobacillus bulgaricus can produce a special yogurt flavor and help enhance digestive function.

3) Streptococcus tropicalis (Streptococcusthermophilus): Streptococcus tropicalis is a common probiotic and is also commonly used in the fermentation of yogurt. It can quickly convert lactose to lactic acid, providing the acidity and flavor needed for yogurt.

These probiotics are fermented with lactose in milk to produce lactic acid during the production of yogurt, which makes the yogurt have a sour taste, rich taste and a certain shelf life.

In addition, these probiotics also help maintain the balance of intestinal flora, enhance immunity and promote digestion and other benefits.

It is worth noting that different brands and manufacturers may use different combinations of probiotics and different production processes to obtain specific flavors and effects. The old yogurt and Greek yogurt that we often buy in our lives have many differences in production methods and taste.

Old yogurt: Old yogurt is a traditional yogurt making method. It is usually obtained by fermenting milk or other dairy products with lactic acid bacteria (such as Lactobacillus acidophilus, Streptococcus thermophilus, etc.). During the fermentation process, lactic acid bacteria will convert lactose into lactic acid, giving yogurt a sour taste and special flavor. The taste of the old yogurt is generally more smooth, consistency in general, sour taste is more obvious.

Greek yogurt: Greek yogurt is a special type of yogurt that is made in a slightly different way than traditional yogurt. When making Greek yogurt, ordinary yogurt is usually filtered through a strainer to remove the whey part of it to increase its consistency and protein content. This process is similar to dehydration, making the texture of Greek yogurt more rich, more thick taste, compared with traditional yogurt more smooth, relatively light sour.

In short, old yogurt is a traditional yogurt obtained from fermented dairy products, which has a smooth and sour taste. Greek yogurt is yogurt that has been filtered to remove whey, which has a thicker texture and a thicker taste. The two differ in taste and texture and can be chosen according to personal preference.