Mulberry grapes are usually boiled for 30-90 minutes. Before boiling mulberry, it is necessary to soak the mulberry in salt water for a period of time, because the pulp of mulberry is easy to be mixed with stains, and these stains can be removed after soaking in salt water, so that the mulberry juice will be clear and free of impurities when boiling. The main nutritional components of mulberry are sugar, water, ash, crude protein, crude fiber, soluble inorganic substances and so on. In addition, mulberry also contains essential amino acids, easily absorbed polysaccharides, rich vitamins, red pigments and minerals such as iron, calcium, zinc and selenium that the human body lacks.