Different Varieties of Water Caltrop (Trapa bispinosa) Starch: Physicochemical Properties and Digestibility Modulated by Its Multi-Scale Structure

This study assessed the physicochemical properties and digestibility of starches derived from five varieties of water caltrop, focusing on their multi-scale structure. Water caltrop starch granules exhibited round, oval, or polygonal shapes with smooth surfaces, exhibiting unimodal particle size distributions and A-, C-, or C/A-type crystal patterns. <i>T.qR'Green'</i> exhibited the highest amylose content (30.93%), the lowest peak viscosity and breakdown, and the highest setback. <i>T.bR'Green'</i> had the highest crystallinity (29.04%) and endothermic enthalpy (15.39 J/g), with a more ordered internal structure. <i>T.bR'Red'</i> had the lowest crystallinity (24.94%), gelatinization temperature, and endothermic enthalpy (8.08 J/g), while showing the highest peak viscosity and breakdown, the lowest setback, and the highest resistant starch content (47.2%), thus possessing stronger resistance to digestion. Pearson correlation analysis revealed that the thermal properties of water caltrop starches were mainly influenced by the amylopectin B-chains and short-range order, while pasting properties were mainly affected by amylopectin B-chains and crystallinity. Amylose content positively influenced solubility but negatively affected swelling power. Additionally, water caltrop starch digestibility showed a negative correlation with granule size and short-range order. These findings indicated the significant impact of starch multi-scale structure on physicochemical properties and digestibility.