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This paper discusses the determination of kinetic parameters for the thermal death kinetics of rusty grain beetle in stored wheat using the temperature history of wheat during 50-Ω RF heating. At 353 K, a 100% insect mortality rate was achieved at all three moisture content levels tested. At 343 K, a 100% insect mortality rate was achieved at the 15% and 18% moisture contents. Increases in the target temperature and moisture content of the wheat samples significantly increased the mortality rate of the insect pests. The thermal death kinetics of the rusty grain beetle during 50-Ω RF heating followed a 1st order reaction. The value of Ea was 97.490 J/mol, and the value of k0 was 6.74 × 1013 1/s. There was good agreement between the experimental mortalities and the simulated mortalities based on the thermal kinetic model.

Adult Tribolium castaneum infesting canola seeds at 9% moisture content were treated using a 50-Ω radio frequency heating system and the thermal mortalities of the insects were determined. The infested seeds were treated at temperatures of 24–65 °C with radiofrequency (RF) heating power at 3 kW, 5 kW, and 7 kW. More than 80% of the insects were killed at 65 °C at all the three power levels. The survival rate of the adult T. castaneum decreased with temperature and RF power level. The effect of selective heating on mortality of insects increased at the higher RF powers. An inverse simulation was used to estimate the kinetic parameters of thermal death in adult T. castaneum. The thermal kinetic models developed in this study were solved using the 4th order Runge-Kutta method on a MATLAB platform. The thermal death kinetics for adult T. castaneum followed the 1st order reaction with Ea of 97.50 kJ/mol and k0 of 6.5 × 1013. The lethal time (LTs) calculated using the thermal death kinetic model developed in the study agreed well with the LTs determined experimentally.

A pilot-scale 50-ohm (Ω) radio frequency (RF) heating system was used to determine the temperature distribution of bulk canola seeds (Brassica napus L.), 9% moisture content (MC) wet-basis (w.b.) in a tubular applicator with parallel electrodes. Non-uniformity of the temperature distribution of bulk canola was observed during the RF heating process of the canola seeds. The hottest spot was observed at the front side of the tubular cavity of the applicator adjacent to the hot electrode. Tavg of the canola seeds was 38 °C, 42.2 °C, and 40 °C at 3 kW, 5 kW, and 7 kW respectively. Temperature distribution was relatively uniform in the back zone (0.287, 0.433, and 0.278 for 3 kW, 5 kW, and 7 kW respectively). The physicochemical properties of canola seeds changed significantly after 50-ohm RF heating at various end temperatures and power levels. Industrial relevance text Radio frequency heating is an emerging technology and has immense potential in food grains, pulses, and oilseeds processing. The radio frequency heating can be used for disinfestation of insects, drying, and removal of anti-nutritional compounds in stored food grains, pulses, and oilseeds. Radio frequency heating is based on dielectric heating principle thus allowing selective and volumetric heating. The radio frequency waves have wavelengths ranging from 1 mm to about 100 km with a frequency of 3 kHz to about 300 GHz, the penetration depth is comparatively higher than microwaves, which has wavelengths ranging from 1 mm to about 1 m with frequencies between 300 MHz and 300 GHz. Thus, radio waves penetrate larger volume objects compared to microwaves. This research investigated a 50-ohm radio frequency heating system with a through field parallel plate type applicator to observe the temperature distribution throughout the bulk canola at different power levels. Understanding the characteristics of 50-ohm radio frequency heating of bulk canola seeds at different power levels can help design effective heating processes involved in canola seeds storage and handling.