Old tofu. North tofu is another name of old tofu, which mainly uses bittern as coagulant. It is characterized by high hardness and toughness, and the water content is about 80% to 85%. Because of its hard texture, the taste of North tofu is slightly rough, which is suitable for frying or frying, and can fully show its tough taste and rich nutritional value. Tofu is a kind of food with rich nutrition and a long history. The public's love for tofu has promoted the progress and development of tofu production technology. The main production process of tofu is pulping, that is, soybean is made into soybean milk; The second is solidification, that is, soybean milk solidifies into a gel containing a lot of water under the action of heat and coagulant, that is, tofu. Tofu contains a variety of trace elements necessary for human body, and is also rich in high-quality protein, which is known as "vegetable meat". The digestion and absorption rate of tofu is above 95%, and this kind of healthy food has always been loved by everyone. However, if we want to give full play to the nutritional value of tofu, we need to pay attention to good collocation. In 20 14, "Traditional Tofu Making Techniques" was selected into the list of the fourth batch of national intangible cultural heritage representative projects in China, and this magical China cuisine began to be endowed with more cultural connotations and inheritance significance beyond the commodity value.