Effects of polysaccharide charge characteristics and molecular architectures on the gel properties and in vitro digestibility of heat-induced sesame protein gels

Abstract

This study investigated how polysaccharides with distinct charge characteristics and molecular architecture modulate the heat-induced gelation behavior and in vitro digestibility of sesame protein (SP). Six representative polysaccharides, including guar gum (GU), locust bean gum (LBG), high-acyl gellan gum (GG), gum arabic (GA), κ-carrageenan (KC), and xanthan gum (XG), were incorporated into SP, and the resulting composite heat-induced gels were evaluated for their gel properties, microstructure, and digestibility. Among the tested polysaccharides, linear anionic polysaccharides with rigid helical conformations, KC and GG, formed the densest and most continuous gel networks. These systems exhibited significantly enhanced viscoelasticity, increased water-holding capacity (WHC) by 34.8–36.8%, and reduced water mobility. These improvements were accompanied by increases in surface hydrophobicity (7.4–8.5%), β-sheet content (37.0–40.7%), and crystallinity index (182.1–201.8%). Such structural modifications restricted enzymatic access, reducing gastric and intestinal digestibility by up to 40.9% and 18.6%, respectively. In contrast, the branched anionic polysaccharide XG and the neutral flexible polysaccharides GU/LBG formed relatively weak, heterogeneous, and porous networks, resulting in only modest improvements in gel properties. Notably, GA, characterized by low negative charge density and high branching, acted antagonistically by hindering gel formation and reducing WHC by up to 37.8%, with negligible effects on digestibility. Collectively, these findings demonstrate that the charge characteristics and chain architecture of polysaccharides are critical determinants of SP gelation and digestion behavior. Tailoring these structural features offers a promising strategy for designing sesame protein-based gels with tunable texture and digestibility for applications in structured foods and controlled-release delivery systems.