Forces involved in freeze-induced egg yolk gelation: Effects of various bond dissociation reagents on gel properties and protein structure changes

Urea, sodium dodecyl sulfate (SDS) and beta-mercaptoethanol (2-ME) were used to monitor the roles of hydrogen bonds, hydrophobic interactions and disulfide bonds in frozen egg yolk. Yolk samples were prepared with a denaturant, and the textural characteristics, turbidity properties, protein patterns and structures were analysed. The results showed that SDS or 2-ME addition to egg yolk promoted its turbidity and texture properties, but urea changed the turbidity differently. SDS-PAGE results showed that yolk protein patterns with urea slightly reduced the amount of high molecular weight substances, whereas SDS and 2-ME addition increased the amount. ATRFTIR spectroscopy revealed that the protein secondary structures changed from ordered structures to random coils. The texture properties were correlated with the protein secondary structure, especially beta-sheets and beta-turns. Thus, the three bond dissociation reagents induced protein denaturation. Hydrogen bonds were the critical force affecting frozen egg yolk gelation, followed by hydrophobic interactions and disulfide bonds.

Automated summary

Urea, SDS, and 2-ME play important roles in determining the properties of frozen egg yolk by affecting hydrogen bonds, hydrophobic interactions, and disulfide bonds. Hydrogen bonds are the critical force affecting the gelation of frozen egg yolk, followed by hydrophobic interactions and disulfide bonds.