Effects of psyllium polysaccharide with different molecular weights on the digestibility, physicochemical properties...

The effects of psyllium polysaccharides (PP) with different molecular weights (Mw) on the physicochemical characteristics, interaction forces, and digestibility of rice starch (RS) are methodically examined in this work. High-Mw PP (H-PP) (3.83 × 106 Da), medium-Mw PP (M-PP) (8.39 × 104 Da), and low-Mw PP (L-PP) (9.28 × 103 Da) were fractionated, characterized, and added to RS to clarify their effect on starch digestion. The results indicate that H-PP exhibited the most pronounced inhibitory effect on enzymatic hydrolysis, leading to a significant reduction in the estimated glycemic index (eGI) by enhancing the crystalline structure and short-range molecular order of RS. Mechanistic investigation revealed that PP molecules interact with RS through hydrogen bonding and electrostatic interactions, forming a structural barrier that impedes enzymatic accessibility. The intensity of these interactions was greatest in RS-H-PP and gradually decreased in RS-M-PP and RS-L-PP, corresponding with an increase in starch digestibility. These findings provide mechanistic insights into the molecular interactions regulating polysaccharide-starch systems and establish a theoretical basis for the development of functional starch-based foods with controlled glycemic responses.