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

蛋白质磷酸化已被用于改善食品蛋白质的功能特性。此外，可以制备增强钙吸收的功能性蛋白质。近年来，随着磷酸基团在生理和免疫功能中的作用的报道，人们期望蛋白质的这些功能特性也可以通过磷酸化来增加。因此，在正磷酸盐或焦磷酸盐（PP）存在下，通过干热使EWP磷酸化。在pH 4.0、85℃下干热5d后，EWP的磷含量为1.05%，高于酪蛋白。EWP的电泳迁移率依赖于磷酸化水平。引入的磷酸键在pH 2-10下是稳定的。~ 1 <31>P NMR和PP-磷酸化蛋白质经酶、酸或碱处理的脱磷酸化结果也支持N-P键的存在。磷酸化可提高乳化活性和乳化稳定性。PP-EWP的消化率提高，磷酸化作用使EWP具有增溶磷酸钙的能力。在0. 1% PP-EWP溶液（pH7.0）中，95℃加热10 min，可溶性蛋白质含量仍在95%以上，热稳定性显著提高。此外，PP-EWP的成胶性能也得到了改善，得到了透明、致密、持水性较好的热致凝胶。PP-EWP对磷酸钙的增溶作用可能是其促进小肠钙吸收的主要原因。因此，在焦磷酸盐存在下干热磷酸化是改善EWP功能特性的有效方法

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