FUNCTIONAL-PROPERTIES OF CHEMICALLY PHOSPHORYLATED WHOLE CASEIN

The functional properties of unmodified whole casein were compared wit h those of casein that had been chemically superphosphorylated using p hosphorus oxychloride at three different pH values. Casein modified at pH 5, 7, and 9 had an additional 3.30, 4.78, and 6.75 mol of P bound/ mol of casein, respectively, either as monophosphates when modified at pH 5 and 7 or as mono-, di-, and polyphosphates when modified at pH 9 . Solubility studies indicated that the isoelectric point of the modif ied caseins shifted to the acid side of pH 4.6 as the amount of bound P increased. None of the modified caseins was as soluble in water at p H 7 as the unmodified control, and caseins modified at pH 5 and 7 had lower solubility than casein modified at pH 9. Compared with control c asein, casein modified at pH 9 was more soluble in the presence of Ca2 +, and caseins modified at pH 5 and 7 were less soluble. Superphosphor ylated caseins had improved foam stability and poorer emulsion stabili ty than the controls. Superphosphorylation of whole casein altered the ability of the casein to interact with its environment, as demonstrat ed by the changes in its functional properties, which could be of valu e in creating or improving food products.