Modulation of in vitro digestibility and gut microbiota fermentation profiles of different V-type starch-resveratrol complexes fabricated via heat-moisture treatment.

V-type starch (type 5 resistant starch, RS5) is a promising dietary component for metabolic health, yet structure-function relationships among its crystalline subtypes under polyphenol modulation remain unclear. In this study, three V-type starch variants (V6, V7 and V8) and their resveratrol (RA) complexes were prepared via heat-moisture treatment (HMT) using ethanol, tert-butanol and salicylic acid as guest molecules. The multi-scale structures, in vitro digestibility, molecular interaction and fecal fermentation characteristics were systematically evaluated. XRD confirmed the successful induction of V6, V7, and V8 crystalline patterns. RA incorporation dose-dependently increased relative crystallinity and V-type crystal content. V8 complexes exhibited the highest RA complexation ratio and resistant starch content (28.03%), whereas V7 complexes preferentially formed slowly digestible starch. Molecular dynamics simulations revealed that salicylic acid possessed the strongest binding affinity to amylose, and the stable V8 helical cavity accommodated two RA molecules via hydrogen bonding and van der Waals interactions. In vitro fecal fermentation demonstrated that V6 and V8 complexes significantly boosted short-chain fatty acid production and enriched beneficial Faecalibacterium and Bifidobacterium, whereas V7 complexes stimulated opportunistic pathogens (Escherichia and Citrobacter). These findings clarify the molecular basis of V-type starch-polyphenol interactions, providing a rational framework for designing starch-based functional foods.