Effects of stewing with tea polyphenol on the gel properties, microstructure, and secondary structure of boiled egg white

This study aimed to investigatethe mechanism of stewing with tea polyphenols (TP) on the properties of boiled egg white gel (BEWG). The results indicated that, during the stewing process, soluble protein and hardness showed an overall increasing trend, while surface hydrophobicity showed a decreasing trend with blue-shift. The free sulfhydryl group showed that TP could promote the formation of disulfide bonds, and the position of immobilized water at T-2 showed a decreasing trend. Environmental scanning electron microscopy and SDS-PAGE showed that the protein gel aggregation degree increased. Moreover, Fourier transform infrared spectrometry showed that protein polarity increased and that alpha-helices, beta-turn, intramolecular beta-sheets, as well as intermolecular antiparallel beta-sheets showed an increasing trend. Generally, TP strengthened protein aggregation by promoting the formation of disulfide and hydrogen bonds, thus enhancing the gel strength of BEWG. Moreover, the secondary structure of proteins became more stable under the action of TP, and the higher the concentration of TP, the greater the effect on BEWG. Practical Application TP, an ideal, cheap, and safe natural food additive, can be applied to the processing of egg products because the addition of TP can significantly improve the gel strength of egg white.