Effects of different plant proteins on the quality and characteristics of heat induced egg white protein gel under freezing conditions

Abstract

Eggs white is rich in protein, whose gel property is one of the most important functional characteristics during processing. The purpose of this study was to reveal the effect of different plant proteins (2% (w/w), 2.5% (w/w), 3% (w/w)) on the quality of heat induced egg white protein (EWP) gel after freezing. Gels were prepared by adding 2.5% soy protein isolates (SPI) or pea protein isolates (PPI), and then were frozen for 14 days. Compared with the control group (EWP without adding any plant proteins), the hardness, chewiness and gumminess of SPI-EWP gel were increased by 58.23%, 71.11% and 66.35%, respectively, which was better than PPI-EWP. The thawing loss rate of SPI-EWP and PPI-EWP gel decreased by 16.8% and 13.0%, respectively, and the centrifugal loss rate decreased by 13.2% and 11.8%, respectively. The addition of plant proteins resulted in a decrease in the proton signal intensity of the T23 peak. Hydrogen proton imaging and rheology results showed that water content of gels added with plant proteins after freezing was higher than control group and showed better viscoelasticity (SPI was better than PPI). The results of intermolecular forces indicated that with the increase of plant protein, the ionic bonds decreased, the contribution of disulfide bonds significantly increased (p < 0.05). Fourier Transform Infrared Spectroscopy (FTIR) indicated that the α-helix content decreased, β-sheet increased. In brief, this study provides valuable reference for the development and application of plant protein to improve the quality of egg white protein in food industry.