Analysis of microwave irradiation on the lethal conditions for insect pest in rice and its influence and regulation on the quality of rice

Abstract In view of the problem that conventional insecticidal methods cannot inhibit the hatching of insect eggs in rice, microwave heating was used to kill the insect eggs hidden in the rice grains. The lethal conditions of microwave irradiation on insect pests in rice and the effects of microwave irradiation on the quality of rice were studied, and the process conditions that can both ensure the quality of rice and kill insects were put forward. The microwave energy density parameter was used to evaluate the lethal conditions of microwave irradiation for insect pests in rice. The results showed that the lethality ratio of insect pests was 100% when the microwave energy density was higher than 0.0325 kW h/kg. Both microwave power density and microwave power affected the quality of rice. The results concluded that the cracking ratio, chalkiness and amylose content were increased with the increase of microwave power at the same microwave power density, while the free fatty acid content was decreased. Through the study of variable microwave power process, it was found that the cracking ratio and chalkiness can be controlled below 1.5% when the heating rate of rice at the later stage of microwave irradiation was less than 0.2 °C/s. The use of two-stage variable microwave power process can eventually ensure the disinfestation and the quality of rice simultaneously.