Understanding of the digestibility differences of gelatinized starch under various concentrations

Hydrothermal treatments have been shown to significantly alter starch digestibility and the associated postprandial glycemic response following consumption. However, the concentration-dependent effects of thermal processing on starch digestion kinetics remain poorly characterized. This study systematically investigated the impact of RVA shear-induced gelatinization at varying concentrations (1%-30%) in aqueous system on the in vitro simulation digestibility of starches from diverse botanical sources. Crystalline structure and amount were analyzed via X-ray diffraction and differential scanning calorimetry. Shearing thermal treatment induced complete disruption of ordered crystalline domains and substantially increased starch digestibility at lower concentrations (≤5%), with resistant starch (RS) and slowly digestible starch (SDS) fractions totaling <30%. In contrast, samples gelatinized at a high concentration (30%) demonstrated maximum digestion resistance, yielding elevated SDS and RS fractions (∼77%). The densely packed molecular architectures formed during high-concentration gelatinization markedly reduced enzymatic susceptibility, exhibiting lower digestibility than low-concentration counterparts. This concentration-dependent structural modulation highlights practical significance for engineering starch digestibility in ready-to-eat foods.