The role of metal compounds in dynamically regulating alkali infiltration during pickling of preserved eggs

This study was conducted to investigate the dynamic regulation of alkali infiltration by different metal compounds during the pickling of preserved eggs. With the increased pickling time, the alkalinity of the pickling solution decreased, while the pH of preserved egg white increased firstly, then decreased, and finally increased again. The metal ions corresponding to the added metal compounds (CuSO4, CuSO4/ZnSO4 and PbO) underwent a complex migration with pickling time, and their content gradually increased in eggshell and yolk, but showed complex changes in egg white. The addition of metal compounds could produce a plugging effect. The main components of the black spots on eggshells of preserved eggs pickled by CuSO4, CuSO4/ZnSO4, and PbO were Cu2S, Cu2S/ZnS and PbS, respectively. In short, different metal compounds were combined with H2S to form insoluble compounds to block eggshell stomata, mesh pores and corrosion pores, thereby dynamically regulating the penetration of alkali.