Dynamic in vitro gastrointestinal simulation resolves digestion-induced structural transitions of retrograded lotus...

Static in vitro digestion models are widely employed to assess starch digestibility, but their simplified conditions may not adequately simulate physiological processes. In this work, an in vitro dynamic human gastrointestinal digestion system, designed to replicate the sequential phases of the human gastrointestinal tract, was used to track the structural evolution of retrograded lotus seed starch (RLS) during digestion. The results showed that the dynamic digestion system effectively reflected the temporal changes in starch hydrolysis, with enzymatic efficiency during the intestinal phase surpassing that of the gastric phase. Throughout digestion, the initially smooth surface of the RLS samples transformed into a distinctly rough and irregular morphology. After gastrointestinal digestion, the relative crystallinity and the degree of short-range order of the RLS samples increased significantly by 37 % and 53 %, respectively, which was responsible for their enhanced thermal stability. These structural changes were associated with the degradation of amorphous regions and rearrangement of amylose double helices driven by enzymatic hydrolysis. These findings would provide insights into digestion-induced structural evolution of the RLS samples, offering implications for the targeted development of prebiotic ingredients.