Heat-induced gel formation by whey protein isolate-deacetylated konjac glucomannan at varying pH conditions

Abstract

This study explored the formation of composite gels via pH-modulated whey protein isolate (WPI) and deacetylated konjac glucomannan (KGM) solutions. The physicochemical properties, gelation characteristics, and microstructure of WPI-KGM gels were evaluated at varied pH levels (2−10). Findings revealed that WPI and deacetylated KGM failed to generate a stable gel at pH extremes (2 or 10). However, under optimal pH conditions (4 or 8), the WPI-KGM system yielded gels exhibiting superior water-holding capacity and hardness after heat treatment, with the composite gel at pH 4 demonstrating enhanced whiteness compared to that at pH 8. Textural and rheological assessments suggested that moderate pH levels favor the formation of well-structured gels. Scanning electron microscopy showed denser structures at pH 4 and 8, contrasting with disordered, coarse gel networks at pH 2 and 6. At pH 4, the WPI-KGM gel structure was primarily maintained by electrostatic and hydrophobic interactions, whereas at pH 8, disulfide bonds became pivotal. Overall, our findings underlined the importance of appropriate pH conditions in facilitating composite gel formation, offering practical insights for heat-induced gel material development in the food industry.