Hydrothermal Treatment of Water Yam Starch in a Non‐granular State: Slowly Digestible Starch Content and Structural Characteristics

Abstract: Gelatinized water yam starch was subjected to hydrothermal treatment (25, 30, and 35% moisture content for 1, 8, 16, and 24 h at 100 °C) and characterized by X‐ray diffractometry, solid‐state 13 C cross‐polarization and magic‐angle spinning nuclear magnetic resonance, differential scanning calorimetry, and digestibility analysis. The slowly digestible starch (SDS) content of the starch treated at 30% moisture content for 24 h reached 49.1%, 31.9% higher than that of the control starch. The B‐type pattern of native starch was re‐crystallized to the A‐type by hydrothermal treatment. The SDS content showed negative correlations with T o , T p , T c , and T r , but showed a positive correlation with melting enthalpy. Furthermore, SDS was positively correlated with hydrothermal reaction time, moisture content, relative crystallinity, and the double‐helix proportion. The structural changes in hydrothermally treated water yam starches resulted in the enhancement of SDS. Practical Application: The hydrothermally treated water yam starch could be used as a food ingredient for slow‐energy supply or dietary fiber.