(Kurrol's salt)

(KP03)„ (n > 1,000)

Metaphosphate Sodium trimetaphosphate (STMP) (NaP03)3 Source: Refs. 9 and 10.

"Also known as sodium polyphosphates, glassy in Food Chemicals Codex.

Metaphosphate Sodium trimetaphosphate (STMP) (NaP03)3 Source: Refs. 9 and 10.

"Also known as sodium polyphosphates, glassy in Food Chemicals Codex.


Sequestration is the process of inactivating metal ions by forming soluble complexes. Polyphosphates chelate metal ions, thereby preventing the ions from entering into further (often undesirable) reactions. For example, polyphosphates inhibit the development of rancidity in oils and fats caused by iron (Fe3 + ) catalyzed oxidation. The formation of precipitates and haze in beverages is eliminated by the addition of polyphosphates. Calcium ion sequestration aids in the removal of shells from shellfish and in the extraction of pectin from fruit.

Adsorption—Ionic Interaction

Phosphates (especially more basic condensed salts such as STP) may adsorb or complex with proteins and starches by virtue of their high charge. The charge and the extension of the protein is altered, thereby affecting its colloidal properties. Phosphates can, therefore, act to modify the processing characteristics or stability of proteins, for example, dispersion and peptization in dairy applications, improvement of water retention in meats, and emulsion stabilization in sausage and process cheese.


The major function of phosphates in the baking industry is as leavening acids. Leavening is the process of making baked goods light by expanding or inflating the batter or dough during baking. Three general methods of leavening are employed: fermentation or yeast leavening, chemical decomposition, and chemical neutralization. In chemical neutralization, bicarbonate is neutralized by an acid salt such as monocalcium phosphate monohydrate (MCP). Although any acid component can be used to neutralize the bicarbonate, phosphate salts are preferred as they are manufactured to give controlled rates of reaction. The user can select the appropriate phosphate salt(s) so that carbon dioxide (C02) is released at the appropriate point in the baking process. Usually, C02 release will be desired during both mixing and while baking in the oven. Types of bakery product that are chemically leavened are listed in Table 2 along with typical use levels of sodium bicarbonate (10,12). The phosphate is used at a level to neutralize the bicarbonate. Other applications for phosphates in the baking industry include yeast food nutrients and dough conditioners.

Meat Industry Applications

The meat industry uses phosphate salts in processed meat, poultry, and seafood products to contribute a number of functionalities: pH change, buffering, sequestration of ions, and protein modification. The beneficial effects include an increase in water binding, which improves yield and reduces drip loss; emulsification of fats; solubilization of fibrous proteins, texture modification; flavor enhancement; color stabilization; and reduced rates of rancidity development. Increased pH and ionic strength modify pro tein properties to improve water-binding capacity. Applications in the meat, poultry, and seafood industries are summarized in Table 3.

Depending on the specific application, phosphates can be added to the muscle tissue in a number of ways. For most products, the phosphate is added in a pickling or curing solution by injection, vacuum tumbling, or through immersion of the tissue. It is important that the addition of the phosphate be followed by techniques to improve dispersion of the solution such as massaging or tumbling. This ensures uniformity and maximum yield and avoids localized pH effects, such as color change. U.S. Department of Agriculture (USD A) regulations do not allow phosphates to be added to fresh, uncooked meats or sausages. Phosphates are only permitted in frozen or processed meat products.

Dairy Industry Applications

In dairy processing, phosphates act as emulsifiers or melting salts accomplishing emulsification through protein modification. They help disperse ingredients in milk-based beverages and serve as acidifying and buffering agents in cheese production. Phosphates also prevent protein dena-turation in dried and canned milks and coffee whiteners. In other applications, such as instant puddings or whey protein isolates, the ability of phosphates to promote the formation of protein complexes is used. By far the largest use of phosphates in the dairy industry is in the production of process cheese. In this application the phosphates modify proteins by sequestering calcium ions and adjusting pH. The modified proteins emulsify fats present in the cheese. As a result, the cheese is more uniform in flavor and exhibits controlled melt spread, and the fat does not separate when the cheese is melted. Some of the major applications for phosphates in the dairy industry are described in Table 4.

The Food and Drug Administration (FDA) standards of identity for process cheese, cheese food, and cheese spread allow phosphates to be added up to 3.0% by weight of the finished product. Phosphates permitted include disodium phosphate (anhydrous and dihydrate), trisodium phosphate (anhydrous and dodecahydrate), tetrasodium pyrophosphate, sodium hexametaphosphate, monosodium phosphate, and sodium acid pyrophosphate.

Miscellaneous Applications

Phosphoric acid and phosphates are useful as acidifying and buffering agents in beverages, preserves, and gelatin products. Powdered products may benefit from the flow-conditioning properties of tricalcium phosphate. Phosphates are used in a number of health-related applications where they contribute nutritional supplementation and fortification. Calcium and magnesium phosphates are used in infant foods for mineral supplementation. Calcium phosphates have also been used in several vitamin formulations. Both dicalcium phosphate (DCP) and tricalcium phosphate (TCP) have been used as excipients for tablets. In isotonic drinks, potassium orthophosphates are used to reestablish electrolyte balance. A summary of miscellaneous applications is listed in Table 5.

Table 2. Leavening Applications of Phosphates
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