Formation of soy protein isolate–xanthan gum eutectogels induced by natural deep eutectic solvents: Effects of hydrogen-bond donor type and acceptor-to-donor molar ratio

Hydrogen-bond donor type and molar ratio regulated eutectogel properties. • Fructose-based NADESs improved texture and nonlinear rheological behavior. • Hydrogen bonding and hydrophobic interactions stabilize the gel network. • NADESs induced protein rearrangement and molecular association in the gel matrix. Natural deep eutectic solvents (NADESs) have attracted increasing attention as green and tunable media for constructing functional biopolymer gels. However, the composition-dependent regulation of protein–polysaccharide gel networks by NADESs remains unclear. In this study, NADESs were prepared using choline chloride as the hydrogen bond acceptor and glycerol, fructose, or lactic acid as hydrogen bond donors (HBDs) at different molar ratios (1:1, 1:2, and 1:3). These NADESs were subsequently combined with soy protein isolate (SPI) and xanthan gum (XG) to fabricate nine eutectogels. The choline chloride–fructose (C-F) NADESs exhibited the highest viscosity and the choline chloride–lactic acid (C-L) NADESs provided the strongest acidic environment. The HBD type and molar ratio markedly regulated the microstructure of the eutectogels. Hydrogen bonding and hydrophobic interactions were the main forces stabilizing the eutectogel network to restrict water mobility, while reductions in free sulfhydryl content and surface hydrophobicity indicated protein rearrangement and molecular association within the gel matrix. The C-F NADES at a molar ratio of 1:3 significantly improved the hardness (53.20 ± 0.85 g), cohesiveness (0.70 ± 0.00), gumminess (31.23 ± 0.64 g), and adhesiveness (47.87 ± 0.84 g s) of the eutectogels, while also enhancing their viscoelastic properties and resistance to nonlinear deformation. This study offers a feasible NADES-based approach for designing food-grade protein–polysaccharide eutectogels as tunable soft matrices for the food industry. Download: Download high-res image (310KB) Download: Download full-size image