Sodium Tripolyphosphate (E451i, STPP) in Food: Uses, Safety and Side Effects

How is STPP made?

Polyphosphates are formed from many simple phosphate units linked together, and sodium tripolyphosphate contains three such units.

The brief manufacturing process is as follows:

1. STPP is produced commercially by neutralizing phosphoric acid with sodium hydroxide to form a mixture of monosodium and disodium phosphate.
2. The mixture is then heated to 500-550 °C. This is the reaction equation: NaH2PO4 + 2Na2HPO4 → Na5P3O10 + 2H2O

Food grade STPP exists in two forms and follows the corresponding chemical formula:

1. STPP anhydrous: Na5O10P3
2. STPP hexahydrate: Na5O10P3·6H2O

Specification

What is STPP used for?

With its ability to retain water, the main use of food grade sodium tripolyphosphate is to improve eating quality in food processing, especially in meat and fish products. It is also used in pet foods, such as cat and dog food, for the purpose of binding moisture and keeping animal feed fresh.

It can also be used as a food starch modifier.

Industrial grade STPP has the functions of chelating metal ions, suspending, dispersing, emulsifying, and pH buffering. It is widely used in the production of laundry detergents and dishwashing detergents, industrial water softeners, industrial cleaners, degreasers, leather pretreatment agents, etc. Tanning agents, dyeing auxiliaries, etc.

Let's see its detailed uses in fish and meat.

fish

STPP is a common ingredient added to fish, such as salmon, before freezing, with the primary purpose of reducing the amount of thawing water (or retaining moisture) and making the seafood appear firmer and smoother. You can also find it in other frozen seafood, such as scallops, shrimp, and lobster.

Taste, smell, texture and juiciness are important characteristics of seafood, but most seafood is easily damaged by ice crystals and protein denaturation during frozen storage.

The protein in fish determines its water retention properties. Polyphosphate is a water-retaining agent widely used in seafood to prevent protein denaturation during freezing.

In the production of frozen fish fillets, the fish fillets are soaked in a certain concentration of sodium tripolyphosphate solution for freezing.

The level of water retention performance is closely related to the texture, tenderness, sliceability, elasticity, taste and other qualities of fish products. Without sodium tripolyphosphate, most seafood will easily lose weight (moisture) and develop a darker appearance after thawing, and the body will become brittle.

Meat

Phosphate is widely used in meat processing and its main uses are as follows:

1. Water retention, emulsion stability, juiciness and tenderness
2. Slow down the rate of oxidative spoilage
3. Improve color and preserve flavor

Phosphates commonly used in meat production include sodium polyphosphate, sodium pyrophosphate, and sodium hexametaphosphate.

Polyphosphates are commonly used additives in meat processing. Adding STPP to meat can improve texture and color, reduce cooking losses, and increase product yield. This mechanism is thought to be by increasing pH, enhancing ionic power, and chelating metal ions.

STPP interacts with amino acids or hydroxyl groups in proteins, thereby increasing the water retention and gel strength of meat.

At the same time, its combination with sodium chloride can reduce the sodium content in meat compared to sodium chloride alone. NaCl contains 39.3% sodium, while sodium tripolyphosphate (anhydrous) contains only 31.3% sodium.

Is sodium tripolyphosphate safe to eat?

Yes, food grade STPP is a versatile ingredient that is generally recognized as safe (GRAS) for use in food in accordance with the U.S. Food and Drug Administration's (FDA) Good Manufacturing Practices.

In addition, the safety of STPP has been approved by the European Food Safety Authority (EFSA) and is a food additive authorized by the European Union (EU). It can be used as a carrier in colored anthocyanin preparations and is also suitable for salted fish of the Gadidae family, and Joint FAO/WHO Expert Committee on Food Additives (JECFA) as chelating agents, thickeners and thickening agents.

However, some consumers believe it is harmful to our health because it is a chemical used in detergents that cannot be eaten and has other possible side effects such as allergic reactions.

in conclusion

By now you probably have a good understanding of the production of the food additive sodium tripolyphosphate (E451i, STPP), uses in fish and meat, approved safety, possible side effects, and more.

Have you ever noticed this ingredient on a label in a fish store, seafood restaurant or other kind of food package? Let me know in the comments.