Effects of suppressing protein structural changes on the excellent gelling properties of dried egg white via dry-heat treatment

In this study, we analyzed the molecular properties and thermal behavior of dried egg white (DEW) proteins to understand the mechanisms underlying DEW gel hardening via dry-heat treatment. Dry-heattreated DEW proteins displayed a higher surface negative charge and more isopeptide bonds, such as those in lanthionine and lysinoalanine. In addition, secondary structure and surface hydrophobicity measurements suggested that structural changes that occur during heating in solution were suppressed in dry-heat-treated DEW. The size of the protein aggregates did not change during heating in the diluted solution, and was almost the same as that of the gel structure unit. These results indicated that the structural changes of the protein in solution were restricted due to isopeptide bonds, and that the surface negative charge of the protein caused intermolecular repulsion. Consequently, protein interactions were limited, and the proteins formed a finer and more homogeneous network, which is believed to harden the gel.