1. Classification: Phosphates can be divided into orthophosphate and polycondensed phosphate: orthophosphates refer to various salts of orthophosphoric acid (H3PO4), including M3PO4, M2HPO4, MH2PO4 (M is a monovalent metal ion). Orthophosphates are heated, dehydrated, and condensed to form polycondensed phosphates. Its general formula is Mn+2PnO3n+1, where M represents a monovalent metal ion and n represents the number of phosphorus atoms. When the value of n is large, the limit chemical formula of polycondensed phosphate is MnPnO3n. The various salts of pyrophosphoric acid are called pyrophosphate, namely M4P2O7. The various salts of triphosphoric acid are called tripolyphosphate, namely M5P3O10. The condensed phosphates whose molecules contain more than 3 phosphorus atoms are collectively called polyphosphates, and the number of OPO bonds in molecules is called the chain length of polyphosphates. The molecular formula of metaphosphate is (MPO3)n, which can be roughly divided into cyclic metaphosphate, insoluble metaphosphate and metaphosphate glass (this substance is actually a mixture between chain polyphosphates with a chain length of more than 10 and a small amount cyclic metaphosphates).

2. The phosphates used in food processing are usually sodium, calcium, potassium, and iron and zinc salts as nutrient fortifiers. There are more than 30 kinds of commonly used food-grade phosphates. Sodium phosphate is the primarily consumed food phosphate in China. With the development of the food processing technology, the consumption of potassium phosphate is also increasing year by year. In order to give exert the synergistic function of various phosphates with other additives, and to enable the advancement of food processing technologies, various formulated phosphates are often used as food ingredients and functional additives in practical applications. The research and development of formulated phosphates has increasingly become the future of the development and application of phosphate food additives.