Effects of CaCl2 on salting kinetics, water migration, aggregation behavior and protein structure in rapidly salted separated egg yolks

Salted egg yolks are valued by consumers for their delicious taste good processing characteristics. To improve the quality of rapidly salted separated egg yolks, we compared changes in the salting kinetics, textural properties, water migration, protein aggregation and structure of salted egg yolks in the presence or absence of CaCl2 for 24 h. CaCl2 increased the mass transfer driving force and diffusion coefficient during the salting process; as a result, the salted egg yolks exhibited increased hardness and decreased springiness and cohesiveness. Through low field nuclear magnetic resonance (LF NMR), it was confirmed that CaCl2 promoted the precipitation of lipids and the dehydration of egg yolk. Furthermore, CaCl2 promoted the bulk aggregation of proteins. The analyses of protein structures showed that the contents of β-sheets and irregular curls in CaCl2-salted egg yolk protein increased, while the contents of α-helices and β-turns decreased. CaCl2 affected the microenvironment of tryptophan residues and embedded these residues, enhancing protein aggregation. Based on the comprehensive information obtained in this study, adding CaCl2 to the salting solution improved the degree of protein polymerization in egg yolk; thus, this method might be used to improve the quality of egg yolks separated by salt.