Wash the coarse glass bottle or porcelain bottle (canned food can't be used, because the bottle mouth is too big and easy to be polluted by miscellaneous bacteria), fill it with milk, cover the bottle mouth with a clean double-layer plastic film and tie it with a string. The rope should be loosened, because a lot of steam will be generated in the bottle during heating. If it is tied too tightly, the membrane will rupture and be easily polluted. Boil the glass bottle and milk in the pot for 30 minutes. Soak in water until there is no milk surface. Don't cover it, and then take out fresh pure yogurt that can sell 2%-4% on the market without scalding the back of your hand, such as Jiabao brand pure yogurt and Qinnong brand pure yogurt. After adding the bought yogurt, immediately tie the plastic film tightly to ensure the oxygen-free environment in the bottle.

30。 In the environment above C 10 hour, fresh milk condenses into bean curd, and yogurt becomes instant. Put the yogurt bottle in the refrigerator at 0-5℃ for 2-4 hours, and you can eat it. White sugar can be added during sterilization or when eating, depending on personal taste. You can make a small bottle alone when cooking. If the curd is good, you can keep it as a strain, but you can't use it many times. Because aseptic operation can't be guaranteed at home, you can put the strains in the refrigerator. If the film on the bottle mouth bulges and gas is generated inside, it means that it has entered the gas-producing bacteria, which can only be eaten and cannot be preserved as a strain.