Inline disinfestation of canola seeds from red flour beetles using a 50-ohm RF technology

Disinfestation of insect pests in stored grains is a crucial unit operation to save the quality of the grains during the storage. Several methods of disinfestation are available including chemical and non-chemical methods. However, the use of the chemical method is avoided because of its adverse effects on the environment and studies show that chemical methods have failed frequently in recent years. So, this research focus on investigation of the usage of radio waves, which is a non-chemical method to disinfest insects in stored grains. A pilot-scale 50-ohm radio frequency (RF) heating system was used to disinfest adult red flour beetles (Tribolium castaneum) in bulk canola seeds (Brassica napus L.) of 9 % moisture content (MC) in a tubular applicator with parallel electrodes. The heating characteristics of the bulk canola seeds was studied using the 50-ohm RF system and non-uniformity of the temperature distribution of bulk canola was observed. The hottest spot was observed at the front side of the tubular cavity of the applicator adjacent to the hot electrode. The RF heating rate depends on the distribution of the electromagnetic (EM) field, geometry, and position of the sample in the RF applicator, thermal, physical, and electrical properties of the sample. The average temperature (Tavg) and uniformity index (θ) of the bulk canola during RF heating were also observed. The thermal mortalities of adult red flour beetles infesting canola seeds at 9% moisture content (MC) were determined treated using a 50-ohm radio frequency (RF) heating system. The infested seeds were treated between 297 K and 338 K at RF heating power of 3 kW, 5 kW, and 7 kW. The survival rate of the adult T. castaneum infesting the canola seeds at 9% MC decreased with an increase in temperature (297 K to 338 K) and increase in RF power levels (3 kW to 7 kW). Desirable selective heating effect on mortality was more predominant at higher RF powers. An inverse simulation was used to estimate kinetic parameters of the thermal death of the adult T. castaneum. 4th order Runge-Kutta method was used to solve the ordinary differential equation (ODE) based kinetic model which has an Arrhenius temperature-dependent reaction rate constant. The thermal death kinetics of the adult T. castaneum followed first order reaction with an activation energy of 97.50 kJ/mol. Satisfactory agreements were observed between the mortalities predicted using the kinetic model and the experiments. Also, the physicochemical properties of canola seeds were affected by the RF heating at various end temperatures and power levels although the changes were not very significant and were in an acceptable range. Thus, the research was a successful in disinfesting adult red flour beetles in bulk canola seeds of 9% MC using a pilot-scale 50-ohm RF heating system with a tubular applicator with parallel electrodes