Effect of selected phenolics on egg white proteins subjected to heat treatment

Abstract

The present study investigated the effect of three selected phenolics, gallic acid (GA), tannic acid (TA), and quercetin (Q), on heated egg white proteins. Results revealed that mixing phenolics with egg white before heat treatment at different temperatures (56°C–89°C) for 3, 10, and 20 min, leads to a limitation on the formation of aggregates and a weak loss of solubility as compared to egg white heated without phenolics. These changes can be followed using Native-PAGE and SDS-PAGE to analyze the changes in the proteins in mixes of egg white containing these phenolics as temperature and heating time are varied. The addition of phenolics (GA, TA, and Q) improved the foam stability of heated egg white compared to egg white heated alone. It was found that foam density decreased when Q and GA were added, but that it increased with TA. Practical applications The food industry uses eggs extensively (notably egg white) as an ingredient. In order to avoid the possible microbial contamination, the heat treatment of egg products is often used by the egg derivate industry. The thermal treatment applied to egg white causes modifications in their physicochemical and functional properties. To limit the damaging effects of heat treatment, the addition of polyphenols, at temperatures ranging from 56°C to 89°C and times of 3, 10, and 20 min, could be an industrial alternative in order to increase the stability of proteins. In this study, the addition of selected phenolic compounds revealed that the GA, TA, and Q added to egg white before the heat treatment increase its thermal and foam stability. Q and GA improved foam ability, but it decreased with the addition of TA.