Characterization of Soluble Protein Aggregate and Gel Texture of Dry-Heated Egg White Prepared with Neutral and Alkaline pH

Abstract

　Egg white products dry-heated at neutral and alkaline pH are used as texture modifiers owing to their different gelling properties. In this study, we investigated the soluble protein aggregate (SPA) characteristics and gelling properties of neutral and alkaline dry-heated egg whites (NDEW and ADEW, respectively) with equal protein surface hydrophobicity. ADEW has a lower molecular weight SPA crosslinked by more lysinoalanine and lanthionine bonds than NDEW, indicating that the SPA in ADEW has a higher crosslink density than that in NDEW. Anion-exchange high-performance liquid chromatography followed by polyacrylamide gel electrophoresis revealed that the SPA surface was strongly negatively-charged in ADEW. Moreover, NDEW gel with a fibril structure was harder than ADEW gel with dispersed small aggregates. These results suggest that the molecular weight, crosslink density, and surface negative charge of the SPA vary depending on the pH during dry-heat treatment and are key factors determining the gel textures of NDEW and ADEW.