Effect of cryoprotectants on physicochemical and structural changes in repeated freeze–thawed egg white protein

The effect of cryoprotectants on the changes of physicochemical and structural properties of egg white protein (EWP) caused by repeated freeze-thaw (F-T) cycles was investigated. The cryoprotectants (4% trehalose + 0.3% carrageenan, TC; 1% xylo-oligosaccharide + 0.3% carrageenan, XC; 4% trehalose + 1% xylo-oligosaccharide, TX) were added to the egg white, and stored at F-T for 1, 3, and 5 cycles. The freezing protection effect of cryoprotectants on EWP was discussed by detecting carbonyl contents, total sulfhydryl group content, surface hydrophobicity, water-holding capacity (WHC) of heat-induced gel, SDS-PAGE and the secondary and tertiary structure of protein. The results showed that cryoprotectants could effectively inhibit the increase in surface hydrophobicity and carbonyl contents, and restrict the decrease in total sulfhydryl group content, WHC of heat-induced gel and endogenous fluorescence intensity (p < 0.05). The results can provide reference for the application of cryoprotectants in frozen EWP using in food industry.