2. Mix the whole milk powder with sugar, mix it with water to make sweet milk juice, heat and boil it, remove the milk pan, cover it and cool it.
3. Stir1~ 2 times in the cooling process to prevent milk crust.
4. When it is cooled to about 40℃ (it is advisable not to burn your hands), add the commercially available yogurt as a strain (also called "starter"), stir well with the milk juice, pour it into a clean cup, and cover it tightly with clean paper or cup lid for culture and fermentation.
5. The length of fermentation time varies with different seasons. Generally, it is cultured at room temperature for 5 ~ 7 hours in summer; In winter, the cup can be soaked in warm water of about 40℃ for heat preservation, and cultured for 6 ~10 hour. When the milk is solidified and produces sour flavor, it can be cooled in the refrigerator or cold water to obtain yogurt. The above yogurt can be used as a strain in the next reproduction, and it needs to be replaced with a new strain after 2 ~ 3 times of continuous use. If sugar-containing instant whole milk powder is used, its dosage needs to be increased by 55 ~ 60 grams, and the sugar content can be reduced to 35 ~ 40 grams.