Industrial-scale radio frequency treatments to control Sitophilus oryzae in rough, brown, and milled rice

Abstract

Many previously studies have confirmed that radio frequency (RF) treatments have the potential to be developed as non-chemical alternative disinfestation methods. However, most of them are conducted in laboratory scale RF systems, and it is necessary to scale up the treatment protocol for industry scale applications. A pilot-scale, 27.12 MHz, 6 kW RF system was used to simulate the continuous industrial processing and finally estimate the heating efficiency and throughput for controlling adult rice weevils, Sitophilus oryzae (L.), in milled, brown, and rough rice. An electrode gap (11.5 cm) was chosen based on the appropriate heating rate (6–8 °C/min). RF heating uniformity in the three types of rice samples was improved by adding 50 °C forced hot air surface heating, sample movements on the conveyor belt at a speed of 12.5 m/h, and holding in 50 °C hot air for 6 min. The final industrial RF treatment achieved a complete mortality of adult S. oryzae and provided acceptable quality attributes in moisture content, water activity, color, protein, free fatty acid, and ash. The average heating efficiency and throughput of the RF treatments were 77.7, 76.3, and 74.3%, and 268.8, 247.3, and 224.8 kg/h for milled, brown, and rough rice, respectively. The industrial scale-up studies provide alternative physical methods for disinfesting milled, brown, and rough rice to replace chemical fumigation.