Effect of Heat-Moisture and Annealing Treatments on the Physicochemical Properties and Enzymatic Hydrolysis of Quinoa Starch

Quinoa starch shows promise for low-glycemic foods, but its rapid digestibility and limited processability constrain its application. While heat-moisture (HMT) and annealing (ANN) treatments are widely used for starch modification, their systematic comparison on quinoa starch across moisture and temperature remains unreported. This study therefore investigated the effects of HMT and ANN on the physicochemical properties and digestibility of quinoa starch. Both treatments changed the starch surface structure, weakened the long-range and short-range ordered structures and impaired the freeze–thaw stability of quinoa starch. HMT reduced starch peak viscosity as moisture content increased, while ANN showed a temperature-dependent response: low-temperature ANN (30–40 °C) increased peak viscosity, whereas high-temperature ANN (50–60 °C) decreased it. In vitro digestion results showed that 15% moisture HMT and 50 °C ANN reduced rapidly digestible starch (RDS) to 40.77 ± 0.96% and 48.57 ± 0.90%, respectively. The cumulative intestinal digestion at 120 min decreased from 69.33% (native starch) to 57.06–63.97% for HMT-treated samples and to 58.20–67.29% for ANN-treated samples. These findings provide a practical basis for designing quinoa starch-based foods with tailored digestibility.