Improvement of functional properties of egg white proteins through phosphorylation by dry-heating in the presence of phosphate.

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Protein phosphorylation has been used to improve the functional properties of food proteins. Furthermore, it is possible to make a functional protein enhancing calcium absorption. Recently, as the roles of phosphate groups in physiological and immune function have been reported, it is expected that these functional properties of protein also could be added by phosphorylation. Therefore, EWP was phosphorylated by dry-heating in the presence of orthophosphate or pyrophosphate(PP). The phosphorus content of EWP was 1.05% when it was dry-heated at pH 4.0 and 85℃ for 5 days in the presence of PP, which was higher than that of casein. The electrophoretic mobility of EWP depended on the phosphorylation level. The introduced phosphate bonds were stable at pH 2-10. The results from ^<31>P NMR and dephosphorylation of PP-phosphorylated proteins by treatment with enzyme, acid or alkaline also supported the existence of the N-P bond. The emulsifying activity and emulsion stability were increased by phosphorylation. The digestibility of PP-EWP was increased, and the calcium phosphate-solubilizing ability of EWP was given by phosphorylation. Even being heated at 95℃ for 10 min, the soluble protein was more than 95% in 0.1% PP-EWP solution (pH 7.0), suggesting significantly improved heat stability. Furthermore, the gelling properties of PP-EWP were improved, and a transparent and firmer heat-induced gel with better water hold-capacity was obtained. It is expected that PP-EWP may enhances calcium absorption in small intestine because it solubilized calcium phosphate.In conclusion, phosphorylation by dry-heating in the presence of pyrophosphate is an effective method to improve the functional properties of EWP