Effect of Microwave Treatment on Disinfestation and Physicochemical Properties of Coix Seeds

In this study, microwave treatment was employed for the disinfestation of coix seeds. The effects of microwave power and treatment time on Sitophilus zeamais populations were evaluated at 30 and 60 days of storage. Physicochemical changes in the coix seeds before and after treatment were characterized via scanning electron microscopy, Fourier transform infrared spectroscopy, X-ray diffraction, differential scanning calorimetry, and texture analysis. The increase in the microwave power and treatment time significantly reduced S. zeamais populations (p < 0.05) and concurrently increased the burst rate of the coix seeds (p < 0.05). Regarding the physicochemical properties, increasing the microwave power and treatment time led to a gradual decrease in the relative crystallinity and gelatinization enthalpy; this was attributed to the disruption of the starch crystalline structures, which promoted gelatinization. The hardness of the steamed seeds initially increased and subsequently decreased as the microwave conditions were intensified. Based on the comprehensive evaluation of disinfestation efficacy and physicochemical properties, both 1.6 kW for 30 s and 1.2 kW for 40 s were optimal conditions. Under these conditions, only one S. zeamais individual was detected after 60 days storage, with reasonable burst rates of 14.3% and 11.3%, respectively. Additionally, the treated samples also had significantly lower relative crystallinity and gelatinization enthalpy than untreated ones. In conclusion, microwave treatment under optimized conditions enabled the disinfestation of S. zeamais, extending the shelf life and facilitating the cooking of coix seeds. These findings suggest that microwave treatment is a promising, environmentally friendly, and efficient approach for the preservation of coix seeds.