Structure-function insights into bile acid binding of kiwifruit polysaccharides: Roles of Uronic acids, molecular...

Dietary polysaccharides can sequester bile acids, thereby supporting cholesterol regulation and cardiovascular health, yet the structural determinants of this interaction remain insufficiently defined. In this study, kiwifruit polysaccharides (KFP) were extracted and systematically subjected to simulated gastrointestinal digestion, colonic fermentation, controlled acid hydrolysis, and rheological modulation to evaluate the contributions of key structural features to bile acid-binding capacity (BABC). Sequential digestion and fermentation showed that intestinal digestion and early-stage fermentation enhanced BABC, coinciding with enrichment of uronic acids, particularly galacturonic acid, whereas prolonged fermentation diminished activity. Molecular weight (Mw) analysis revealed a threshold effect: moderate depolymerization optimized BABC by exposing functional groups and increasing accessibility, while excessive Mw reduction disrupted structural integrity and weakened binding. Viscosity further modulated bile acid binding in an Mw-dependent manner: lower viscosity improved BABC in high- and intermediate-Mw polysaccharides but reduced binding when Mw was extensively degraded. Collectively, these findings demonstrate that BABC is governed by the interplay of uronic acid content, Mw, and viscosity, rather than by any single parameter. This work provides mechanistic insight into KFP structure-function relationships and offers a rational framework for developing kiwifruit-derived functional foods or nutraceuticals targeting cholesterol management.