Sodium phosphate refers to various inorganic salts composed of sodium (Na+) and phosphate (PO43−). It is one of the most widely used food additives and commonly used as a quality improver or nutrition enhancer in meat, seafood, baked goods, dairy products and beverages.
Generally, neutralization of phosphoric acid with sodium hydroxide or sodium carbonate are used to produce mono-, di and trisodium phosphates, which are the raw materials to manufacture sodium pyrophosphates and polyphosphates.
When used as food additives, almost without side effects and their safety has been approved by the U.S. Food and Drug Administration (FDA) and European Food Safety Authority (EFSA), as well as the Joint FAO/WHO Expert Committee on Food Additives (JECFA).
Sodium phosphates are multi-functional ingredients commonly with the following functions in food:
Chelating metal ions (e.g. Cu2+ and Fe2+) and therefore preventing the oxidation, discoloration, and decomposition of vitamin C caused by these metal ions, finally prolong food shelf life, reduce cooking time and etc.
Chelating calcium (Ca2+)
Pyrophosphates remove naturally occurring calcium ions from proteins and combine with proteins, and therefore increase the water retention ability of meat products.
Adjust PH in food.
Prevent the separation of protein and fat, increase viscosity, improve the mouthfeel. Such as in processed cheeses.
Polyphosphates prevent protein denaturation, and maintain water retention for frozen seafood (e.g. fish, shrimp) and poultry products.
Combined used with sodium carbonate in bakery to release CO2 to increase the loaf volume.
In industrial applications, they’re commonly used in water treatment, detergents and metal finishing by chelating metal ions.
Sodium phosphates are inorganic feed phosphates (IFP), which are a source of nutrition – phosphorus. Phosphorus is a vital nutrition in animal feed.
It is not only a mineral found in the bones and teeth of animals, but an important substance that participates in the metabolism of cells and blood, which is a must for the growth, fertility and bone development for animals.
The commonly used IFP are calcium phosphates, but sodium phosphates are also used, and some of them have the purpose for retaining moisture and making the feed fresh.
Types of sodium phosphates
Food grade sodium phosphates including three types: sodium orthophosphates, sodium pyrophosphates and sodium polyphosphates.
There are three types of sodium orthophosphates, made of sodium with dihydrogen phosphate (H2PO4−), hydrogen phosphate (HPO42−), and orthophosphate (PO43−), respectively.
1. Monosodium phosphate
MSP, also known as sodium dihydrogen phosphate or sodium phosphate monobasic, can be used as an acid regulator, leavening acid, sequestrant and nutrient supplement in food with the European food additive number E339(i).
It exists in three forms and follows the chemical formula:
- Anhydrous: NaH2PO4
- Monohydrate: NaH2PO4 · H2O
- Dihydrate: NaH2PO4 ·2 H2O
2. Disodium phosphate
DSP, also known as sodium phosphate dibasic or disodium hydrogen phosphate, which can be used as an anticaking agent, flavoring agent, ph control agent, sequestrant, and nutrient in food with the European food additive number for it is E339(ii).
It exists in four forms and follows the chemical formula:
- Anhydrous: Na2HPO4
- Dihydrate: Na2HPO4 ·2 H2O
- Heptahydrate: Na2HPO4 ·7 H2O
- Dodecahydrate: Na2HPO4 ·12 H2O
3. Trisodium phosphate
TSP also known as sodium phosphate tribasic with the European food additive number E339(iii). The food grade is primarily used as an acidity regulator in cereal, and a moisture retainer in meat and seafoods.
It exists in two forms and follows the chemical formula:
- Anhydrous: Na3PO4
- Dodecahydrate: Na3PO4.12H2O
The technical grade is commonly used in cleaners and detergents. Learn more about Trisodium Phosphate
Pyrophosphates (P2O74−), also known as diphosphates, which contains two phosphate groups.
1. Sodium acid pyrophosphate
Abbreviation SAPP, the European food additive number E450(i), with the chemical formula Na2H2P2O7, also known as disodium dihydrogen pyrophosphate, mainly used in three food categories:
- as a leavening acid in baking powder
- maintains the color in processed potatoes
- prevents struvite crystal in canned seafood
2. Trisodium pyrophosphate
Also known as trisodium diphosphate, with the E number E450 (ii), seldom used in food.
3. Tetrasodium pyrophosphate
TSPP, also known as tetrasodium disphosphate or sodium pyrophosphate, with the European food additive number E450(iii), existing in two forms, anhydrous (Na4P2O7) and decahydrate (Na4P2O7 · 10H2O).
The food grade is commonly used as a buffering agent to adjust pH in processed food, and as a calcium sequestrant in meat analogs. It is also used widely in toothpaste to prevent the formation of calculus. Learn more about Tetrasodium Pyrophosphate
A polyphosphate is obtained by a number of simple phosphate joined together, also called condensed phosphates. They’re a kind of hydrophilic ingredient that can stabilize the moisture in food. The commonly used ones in food are sodium tripolyphosphate and sodium hexametaphosphate. They improve the tenderness, taste, texture and yield of fish and meat products by retaining water.
1. Sodium tripolyphosphate
STPP, also known as pentasodium tripolyphosphate or sodium triphosphate, existing in two forms, anhydrous (Na5O10P3) and hexahydrate (Na5O10P3 · 6H2O). The European food additive number for it is E451(i).
The food grade is mainly used in fish and meat products for water retention. The technical grade is commonly used in detergents. Learn more about Sodium Tripolyphosphate
2. Sodium hexametaphosphate
SHMP, the European food additive number E452(i), with the chemical formula Na6P6O18, used as an acidity regulator, texturizer, sequestrant, thickener, and emulsifier in food and commonly can be found in meat & dairy products, and seafood. It is also used in toothpaste and water treatment by chelating metal ions. Learn more about Sodium Hexametaphosphate
Other Sodium phosphates
Sodium aluminum phosphate
SALP, its acidic form (NaAl3H14(PO4)8) is used as a leavening acid with the food additive number E541, while the basic type (Na8Al2(OH)2(PO4)4) is used as an emulsifier in cheese. Learn more about Sodium aluminum phosphate
Sodium calcium polyphosphate
With the E number E452(iii), seldom used in food.
These are cyclic polyphosphates, such as sodium trimetaphosphate, with the chemical formula Na3P3O9.
Now you may have a knowledge of the food additive – Sodium phosphates, from production, uses, types, and so on.
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