Dietary fiber modification by cellulase-AP3 supplementation tailors oat digestion under elderly gastrointestinal conditions with attenuated starch hydrolysis and enhanced polyphenol bioaccessibility.

The resilient fiber matrix of oats limits nutrient release and moderates glycemic response. This study employed a dynamic in vitro stomach-intestine model to investigate how Cellulase-AP3 enzyme supplementation alters oat digestion under simulated elderly conditions. Cellulase-AP3 supplementation caused significant oat matrix disintegration by enzymatically converting insoluble fiber (54.84% to 32.18%) into soluble fiber (50.56% to 59.63%), which in turn elevated digestive fluid viscosity and delayed gastric emptying. This modified physiological environment hindered amylase action, thereby substantially reducing starch hydrolysis from 33.59% to 23.88% and lowering the estimated glycemic index (eGI) from 64.29 to 53.72. Cellulase-AP3 supplementation also enhanced polyphenol bioaccessibility, increasing the release of key phenolic acids (caffeic, vanillic, chlorogenic) above adult-model levels. Factor analysis associated Cellulase-AP3 with a dual improvement in higher soluble fiber/attenuated glycemic impact (F1) and enhanced polyphenol release (F2). These findings establish a novel in situ fiber modification strategy to tailor oat digestion for the elderly.