What is STPP use in seafood

Sodium Tripolyphosphate (E451i, STPP) in Food: Uses, Safety, and Side effectsSodium Tripolyphosphate in salmonPHOSPHATES JUNE 25, 2020 11 COMMENTS
Production | Uses | Safety

Sodium tripolyphosphate (STPP), the sodium salt of the polyphosphate penta-anion, also known as pentasodium tripolyphosphate or sodium triphosphate (different with trisodium phosphate), is a synthetic ingredient mainly used for retaining moisture in fish. The European food additive number for it is E451(i).

How is STPP made?
A polyphosphate is formed by a number of simple phosphate units linked together, and sodium tripolyphosphate contains three such units.

The brief manufacturing processes are as follows (1) :

STPP is commercially produced by the neutralization of phosphoric acid with sodium hydroxide to form the mixture of monosodium phosphate and disodium phosphate.
Then heat the mixture to 500-550 °C. Here is the reaction equation: NaH2PO4 + 2Na2HPO4 → Na5P3O10 + 2H2O
Food grade STPP exists as two forms, and follows the corresponding chemical formula:

STPP Anhydrous: Na5O10P3
STPP Hexahydrate: Na5O10P3 · 6H2O
Specification
Other names
Pentasodium tripolyphosphate
Sodium triphosphate
CAS number 7758-29-4
Appearance White powder or granular powder
Solubility Soluble in water, insoluble in ethanol
PH 9.1 to 10.2 (1 % solution)
What are the uses of STPP?
With the capability of maintaining water, the primary uses of food grade sodium tripolyphosphate are to improve the eating quality in food processing, especially in meat and fish products. It is also applied in pet food (e.g. cat and dog food) for the purpose of binding water and keeping the animal feed fresh.

Sodium polyphosphate is a preservative against bacteria, molds, and yeasts. When used in high concentrations, it can cause skin irritation. Polyphosphates are sequestering and deflocculating agents, primarily in water treatment, food processing, and cleaning compounds; heavy-set detergent builders. Sodium polyphosphate is a preservative against bacteria, molds, and yeasts.

When used in high concentrations, it can cause skin irritation. Polyphosphates are direct food additives and they are used to treat municipal drinking water, but depending upon the concentration and duration of exposure these substances can induce chemical burns.

Sodium triphosphate (STP), also sodium tripolyphosphate (STPP), or tripolyphosphate (TPP), is an inorganic compound with formula Na5P3O10. It is the sodium salt of the polyphosphate penta-anion, which is the conjugate base of triphosphoric acid. It is produced on a large scale as a component of many domestic and industrial products, Food and detergents. Environmental problems associated with eutrophication are attributed to its widespread use.