ABSTRACT
A study of the structural chemistry of the phosphate compounds aids in understanding of some of their reactions in food applications. Structural diagrams are also given for a number of the alkali metal, alkaline-earth metal, and heavy metal compounds of each of the phosphates. The pH titration curves of the various phosphates demonstrate some of their charged anion characteristics. The sodium polyphosphates are able to complex calcium, because the calcium is more firmly bound by the polyphosphate than sodium. In any food applications the stability of the phosphate is of prime consideration. In addition, under similar conditions shorter-chain polyphosphates hydrolyzed slower than longer-chain polyphosphates; thus, tripolyphosphate hydrolyzed more slowly than hexametaphosphate. The cyclic trimetaphosphate first hydrolyzes to tripolyphosphate, the straight-chain compound, which then eventually hydrolyzes orthophosphate. A number of factors affect the rate of hydrolysis or degradation of both chain and ring phosphates to the orthophosphate anion.
