Phosphate is the most widely used food additive in the world. It is widely used in all fields of food production and plays an important role in the improvement of food quality.At present our country has approved the use of phosphate, a total of eight, including sodium tripolyphosphate, sodium hexametaphosphate, sodium pyrophosphate, trisodium phosphate, disodium hydrogen phosphate, sodium dihydrogen phosphate, sodium acid pyrophosphate, jiao 2 sodium dihydrogen phosphate, in food as a supplement to these material can help to varieties of food to improve its color, aroma, taste and shape, and maintain food freshness and quality, and satisfy the demand of the machining process, quality improver in food is very important.Especially in the meat products have an indispensable role.There are many kinds of sodium salt, calcium salt and potassium salt which can be used in meat products, among which the sodium salt of phosphate is the most common.The sodium salts of phosphoric acid include sodium phosphate, sodium pyrophosphate, sodium tripolyphosphate, sodium hexametaphosphate and other polyphosphates. The functions of different kinds of phosphates in meat products are different, but they are mainly used to improve water retention.

         Muscle contains a large amount of water, including bound water, free water and water that is not easy to flow. In every link of meat processing, tissue damage will be caused, resulting in water loss. Therefore, the water content after meat processing is directly related to the quality of the product.The factors that affect muscle water retention are basically the same: the state of myosin.Myosin is the protein in muscle protein that can form hot gel, and its state plays a decisive role in hydrogel retention.During the process of heating, the protein denatures and the molecular structure changes gradually. New forces are formed between the molecules due to polymerization, and the gel network structure is finally formed through cross-linking.The degree of expansion, the rate of degeneration and aggregation, and the interaction among the polymers all affect the hydrogel water retention.

Through the understanding of food additive manufacturers, phosphate affects muscle protein mainly in three aspects:

1. Changing the molecular charge, the electrostatic charge carried by the protein is the fundamental reason for the protein to attract water. The electrostatic charge increases the repulsion force between proteins, thus creating a larger molecular space and increasing water retention.The external manifestation of charge action is pH. When the charge is at the isoelectric point, the space between protein molecules is the smallest. At this time, the pH is around 5, and the water retention of meat products is also the lowest.

2. Chelating metal ions and divalent metal ions are easier to bind proteins. After phosphate chelates metal ions, carboxyl groups in proteins are exposed, which enlarges the molecular space of proteins and improves the binding ability with water.

3. Increase the content of myosin. Phosphate will promote the dissociation of actomyosin and transform it into myosin with gel characteristics, so as to improve water retention.

In the production of meat products, phosphate is an effective activated meat protein moisture retention agent.Phosphates are indispensable to the production and processing of meat products.Phosphate is mainly divided into two aspects, monomer products and complex products.

1) Monomer products: refer to phosphates specified in GB2760 standard for use of food additives, such as sodium tripolyphosphate, sodium pyrophosphate, sodium hexametaphosphate and sodium triphosphate.

2) Compound products: In the current general guidelines of the national standard, it is named as: compound water retention agent, including product names such as commonly known as marinade.