Molecular interactions in the dry heat-facilitated hydrothermal gel formation of egg white protein

A comprehensive investigation was conducted regarding the molecular forces involved in the formation of dry heated egg white protein (DEWP) gels. From the preparation of DEWP powders to the formation of DEWP gels, multiple interactions are involved: the aggregation of DEWP powders in the dry state, the aggregation of DEWP solutions in the water state, and the subsequent gelling process of DEWP gels. The methods included analyses of zeta-potentials, surface hydrophobicity, reducing and nonreducing SDS-PAGE, sulfhydryl (SH) group content, molecular forces, particle size, and critical gel concentration. The results indicated that dry heat promoted the electrostatic and hydrophobic interactions in DEWP and DEWP aggregates. Disulfide (SS) bonds dominated the aggregation process of DEWP solutions in the water state, while hydrophobic and electrostatic interactions dominated the gel forming process. This phenomenon became even more obvious with a longer dry heat time. Furthermore, the intensified molecular interactions induced by dry heat resulted in the formation of smaller gel particles, and a relatively lower protein concentration was required for gel formation. All these factors contributed to the ultimate linear and fine-stranded DEWP gel network, which is more favorable in food processing and application.