How in situ produced dextrans with distinct molecular structures modulate texture and in vitro digestive behavior of mycelium-based high-fiber bread

This study investigated the effects of structurally distinct dextrans produced in-situ by Weissella confusa VIII40 and Pediococcus beninensis DSM 22752 on high-fiber bread containing 50% Cordyceps sinensis mycelium. Fermentation with W. confusa VIII40 yielded 4.86% dextran, significantly improving loaf volume (19%) and reducing crumb hardness (52%) and staling rate (83%), effects not observed with P. beninensis DSM 22752 dextran (2.22%). These improvements were associated with partial solubilization of mycelial fibers and reduced dough stiffness. Fermentation increased soluble phenolics (29%), antioxidant activity (16%), and protein digestibility, while lowering starch hydrolysis and estimated glycemic index. W. confusa VIII40 dextran resulted in the lowest starch hydrolysis and highest bile acid binding, likely through increased digesta viscosity (2.6-fold) and particle size (1.6-fold) during simulated intestinal digestion. Ex-situ dextran addition confirmed concentration-dependent reductions in starch and protein hydrolysis, though less effectively than in-situ synthesis. Overall, in-situ dextran presents a promising strategy for developing high-fiber bread.