Changes in physico-chemical properties, microstructures, molecular forces and gastric digestive properties of preserved egg white during pickling with the regulation of different metal compounds

In this paper, the effects of three different metal compounds, including lead oxide, copper sulfate, mixed compound of zinc sulfate and copper sulfate, on the physico-chemical properties, microstructures, molecular forces and digestion characteristics of preserved egg white were studied. The results showed that different types of metal ions had significant different effects on the penetration rate of alkali into the egg, the moisture content and the viscosity of the preserved egg white. The content of moisture and alkali in the preserved egg white pickled by copper sulfate were the largest among the three treatment groups, and the viscosity change of egg white was the slowest. L* value, a* value and b* value of preserved eggs pickled by copper method were all the largest. The eggs pickled by lead oxide possessed the optimal texture and moderate hardness and good elasticity. The eggs pickled by the mixture of copper sulfate and zinc sulfate possessed the smallest egg white gel mesh and the most compact structure, and the gel hardness was relatively high. The content of disulfide bond in preserved egg white gel pickled by lead oxide was the highest. Although there were no differences among the preserved egg whites pickled with three metal compounds on gastric digestibility, there were different at the different pickling stages. The results showed that different types of metal salts added during pickling could affect the density of the internal structure of preserved egg white gel and the molecular forces, thus changing the physico-chemical and digestive properties of the gel.