Impact of fiber molecular structure on resistance to digestion using the infogest and rat small intestine extract protocols

Purpose Dietary fibers differ in their molecular structure, which influences their breakdown under digestive conditions. This study investigates how fiber molecular structure affects resistance to digestion using in vitro models. Methods High-, medium-, and low-molecular-weight (Mw) corn arabinoxylans, resistant maltodextrin, and inulin were characterized by carbohydrate composition following acid hydrolysis and analyzed for sugar release during simulated digestion using the standardized InfoGest protocol and rat small intestinal extract (RSIE). Results High-Mw corn arabinoxylan (208.8 kDa) remained largely stable, with minor, non-significant increases in glucose and galactose. Medium- (25.5 kDa) and low-Mw (2.5 kDa) arabinoxylans showed partial hydrolysis, with increases in trisaccharides and maltose and decreases in glucose and arabinose. Resistant maltodextrin (1.9 kDa) displayed significant increases in glucose, trisaccharides, and maltose. Inulin (0.75 kDa) remained mostly intact, with only partial decreases in fructose and sucrose. Sugar release during 4 h of simulated digestion followed these trends: high-Mw arabinoxylan released 11.1 mg/g, medium-Mw released 5.20 mg/g/h, low-Mw released 9.84 mg/g, resistant maltodextrin released 6.83 mg/g/h, and inulin released 59.9 mg/g. Conclusion These findings demonstrate that fiber structural variations critically influence the degree of hydrolysis during digestion and the resulting simple sugar release.