Effects of repeated and continuous dry heat treatments on the physicochemical and structural properties of quinoa starch

Repeated and continuous dry heat treatment (RDHT and CDHT, respectively) are new methods for starch modification. RDHT and CDHT were applied to quinoa starch, and their effects on its physicochemical, structural properties and in vitro digestibility of quinoa starch were determined. The results showed that the crystal type of quinoa starch was not change and remained A-type after dry heat treatments. After dry heat treatments, the relative crystallinity, water-solubility, and the pasting parameters of quinoa starch increased, while the swelling power decreased. Relative crystallinity, water absorption index, and percentage of rapidly digestible starch were significantly higher in RDHT starch samples than CDHT starch samples for the same duration. The variation in the infrared absorbance ratio of 1032 cm−1 and 1013 cm−1 was higher for RDHT starch samples than for CDHT starch samples, consistent with their relative crystallinity. Compared with CDHT starch samples, RDHT starch samples showed lower water solubility, swelling power, paste viscosity and thermal parameter values (To, Tp, Tc, ΔT). On the whole, RDHT showed better performance for altering the physicochemical and structural properties of quinoa starch compared with CDHT. DHT can increase the solubility of quinoa starch, and DHT starch with higher peak viscosity can be used as thickener in food.