Developing high-temperature-short-time radio frequency disinfestation treatments in coix seeds: Insect mortality, product quality and energy consumption

Abstract

Radio frequency (RF) treatment is a promising physical insecticidal technique in postharvest grains. The aim of this research was to discuss energy consumption and product quality using high-temperature-short-time RF treatments to completely eliminate Rhyzopertha dominica insect pests in coix seeds. A 6 kW, 27.12 MHz RF system was applied to conduct the thermal treatment, and analyse the mortality of R. dominica in coix seeds under various temperature–time combinations. To achieve the required heating rate and heating uniformity of coix seeds, a rectangular shape container for seeds and 110 mm of electrode gap were selected for RF treatments. Results showed that all the adult R. dominica were controlled when the coix seeds was heated to 50, 53, 56, and 59 °C using RF energy and holding 56.9, 22.8, 7.7, and 0.0 min in ambient air inside the RF cavity, respectively. The moisture content of treated samples decreased with increasing target temperatures except for the treatment when the sample was heated to 59 °C, while the broken rate of coix seeds increased with increasing target temperature. However, no significant difference was found in broken rate, protein, fat content, and colour between control and RF treated samples. To save energy, it was suggested to heat seeds to 50 °C using RF energy and holding 56.9 min in ambient air. To obtain a short processing time, the seeds were heated to 59 °C during RF treatment and holding 0.0 min in ambient air. This research demonstrated that the effective RF treatment holds potential for scaling-up to industrial applications of disinfesting grains. • RF treatments were developed for disinfesting coix seeds based on energy consumption. • A rectangular box for seeds and 110 mm of electrode gap were selected for RF heating. • Complete mortality occurred at 50, 53, 56, and 59 °C for holding 56.9, 22.8, 7.7, and 0 min. • No significant difference in quality was observed between control and treated seeds.