Inhibition of starch gelatinisation by Polygonatum polysaccharides and low-molecular-weight fructans: effects of steam-induced structural modifications.

Abstract

The increasing prevalence of diet-related chronic diseases underscores the need to reduce the glycaemic index (GI) of starch-based foods. In this study, Polygonatum polysaccharides and low-molecular-weight fructans extracted from Polygonatum rhizomes and steamed for 0-24 h were incorporated into rice starch to evaluate their effects on its physicochemical properties. All saccharide treatments significantly reduced paste viscosity, increased gelatinisation temperatures, and decreased gelatinisation enthalpy (p < 0.05). The polysaccharide and low-molecular-weight fructan obtained after 12 h of steaming showed the strongest inhibitory effects, increasing pasting temperatures by 7.6% and 9.4%, respectively. These effects were governed by molecular weight and monosaccharide composition. Rice cakes prepared with the addition of Polygonatum polysaccharide and low-molecular-weight fructan exhibited estimated GI reductions of 8.08% and 9.34%, respectively, without compromising hardness or springiness (p > 0.05). This study provides mechanistic insight and practical guidance for developing lower-GI rice products enriched with Polygonatum saccharides.