Tofu water content is always there, the water content of about 70% of the tofu is suitable for making curd, tofu generally need to add salt to precipitate excess water to achieve the conditions required for making curd, otherwise the hardness can not meet the requirements. In addition, adding salt is not only to make the tofu precipitate water, it can also change the taste of curd, and can prevent the overgrowth of hairy molds and stop the propagation of stray bacteria. Therefore, adding salt is an essential operation in the process of making curd.