Food additives are synthetic or natural substances added to foods to improve the quality of food color, aroma, taste, and the need for corrosion protection and processing techniques. At present, China's food additive has 23 categories, more than 2000 varieties, including acidity regulator, anti-caking agents, defoaming agents, antioxidant, bleaching agent, leavening agent, colorant, color protecting agent, enzyme preparation, flavoring agent, nutritional supplements, preservatives, sweeteners, thickeners, spices etc..