It is not recommended to keep using leftover yogurt as a starter because the longer it is stored, the more harmful colonies of bacteria may develop in the yogurt, so it is recommended to use fresh yogurt as a starter for making yogurt is better.

Generally, when using pure yogurt as a fermentation source, the fermentation time is 6-8 hours; when using yogurt fermentation agent as a fermentation source, the fermentation time is 8-12 hours; the fermentation time is affected by the ambient temperature and the initial temperature of the raw materials, so when the ambient temperature is low or when using refrigerated milk to make the product, it is necessary to prolong the time appropriately. However, the maximum time should not exceed 14 hours. In the summer, put it in the refrigerator to chill, the yogurt will have a pure flavor and excellent taste;