Assessing the Effects of Microwave Treatments on Rice Quality and Mortality of Adult Maize Weevil, Sitophilus zeamais

Abstract

Highlights The study provides insight to microwave technology and the effects of Sitophilus zeamais mortality on rough rice and brown rice that has been previously dried. The mortality of S. zeamais was highest at 5 kW at 90 s, with 98 and 100% mortality for rough rice and brown rice, respectively. Using a microwave power of 5 kW for 90 s on rough rice did not affect head rice yield (HRY), color, or pasting characteristics. For brown rice, a shorter duration of 34 or 60 s at 5 kW or 3 kW for 90 s is recommended to avoid a reduction in HRY. Abstract. A laboratory study was conducted to determine if an industrial microwave could kill Sitophilus zeamais infesting rough rice and brown rice. The rough rice and brown rice samples were comprised of previously air-dried long-grain hybrid (RT 7521 FP) cultivars at initial moisture contents of 11.3 and 12.7% wet basis (w.b.), respectively. Samples (250 g) were infested with ten S. zeamais adults and heated with a microwave power of 3 and 5 kW for 34, 60, and 90 s. The effects of microwave treatments on moisture, head rice yield (HRY), rice color, and pasting characteristics were evaluated. The mortality of S. zeamais was highest at 5 kW at 90 s, with 98% and 100% mortality for rough rice and brown rice, respectively. Rough rice treated at 5 kW at 90 s did result in significantly lower moisture content than the control; however, HRY, color, and pasting characteristics were not significantly different than the controls. Brown rice treated at 5 kW for 90 s resulted in lower moisture content, and there was a significant decrease in the HRY (28.4%) compared to the control (56.2%). No differences in color and some variations in pasting characteristics were observed when compared to the controls. For brown rice, we recommended a shorter duration of 34 or 60 s at 5 kW or 3 kW for 90 s be used to avoid a reduction in HRY and pasting characteristics. Keywords: Brown rice, Maize weevil, Microwave drying, Rough rice.