ABSTRACTChemical phosphorylation of bovine caseins may be useful for changing their physicochemical properties. Depending on the pH of phosphorylation of caseins by phosphorus oxychloride (POCl3), covalent bonds between phosphate groups and different specific amino acids were formed. After casein phosphorylation, intermolecular associations may occur, as shown by electrophoresis. The solubility of modified casein was increased near the isoelectric point (pHi) and decreased at alkaline and acidic pH. In the presence of Ca++at alkaline pH, the solubility of phosphorylated casein was lower than that of the control. Rheological parameters appeared to be efficient indices of structural changes occurring in proteins as a result of chemical modifications. Electron spin resonance studies showed that the flexibility of phosphorylated casein was higher than that of the control.
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