Effect of Soluble Starch on Gelation Properties and Structural Characteristics of Egg White Protein as a Function of Preheating Time

The effects of adding soluble starch (SS) on improving the gelation properties of egg white protein (EWP) were investigated as a function of preheating time (0, 15, 20, 25, 30 and 35 min) at 55 ℃. The texture, water holding capacity, water distribution, surface hydrophobicity, free sulfhydryl content, reducing and non-reducing sodium dodecyl sulfate-polyacrylamide gel electrophoresis patterns, gel strength in the presence of different denaturants, Fourier transform infrared spectra, zeta potential and particle size of EWP and EWP-SS gels were determined. The results showed that the hardness and elasticity of EWP gels increased with preheating time, which increased by 7.06% and 4.21% at 30 min, respectively (P < 0.05). Compared with EWP gels without preheating, addition of SS after 35 min of preheating resulted in a 18.77% and 11.79% increase in the hardness and chewiness, respectively (P < 0.05), and a 4.84% reduction in the water holding capacity (P < 0.05). After preheating treatment for 30 min, the surface hydrophobicity and free sulfhydryl content of EWP increased by 35.17% and 37.00%, respectively (P < 0.05), the intermolecular hydrophobic interaction, disulfide bond and hydrogen bond increased by 1.70%, 3.54% and 15.06%, respectively (P < 0.05), the absolute value of the zeta potential decreased by 22.54% (P < 0.05), the particle size distribution increased, but no new functional groups appeared. Addition of SS after preheating for 30 min increased the surface hydrophobicity and free sulfhydryl content by 36.83% and 52.79%, respectively (P < 0.05) and the disulfide bond and hydrogen bond by 4.97% and 18.82%, respectively (P < 0.05) in comparison with EWP gels without preheating. Meanwhile, it decreased the absolute value of the potential by 6.24% relative to composite gels without preheating (P < 0.05), and further increased the particle size distribution. In summary, compared with untreated EWP, preheating treatment combined with SS can improve the gelation properties of EWP.