Elimination of Cruptolestes Ferrungineus S. In Wheat by Radio Frequency Dielectric Heating at Different Moisture Contents

Abstract

Abstract-Radio frequency (RF) dielectric heating was tested to control Cryptolestes ferrungineus S. in the bulk wheat samples (ca.152 g, dia. = 50 mm, ht. = 100 mm) at the MCs (%, w. b.) of 12, 15, and 18 using a pilot-scale RF heater (1.5 kW, 27.12 MHz) in the batch mode. When the temperature of the hottest spot (geometric center) of the sample, T H was at 80 • C, all the adult insects were found dead at the cold spots, near bottom-wall, at 50.7 to 56.0 • C depending up on the wheat MCs. The temperatures of the insectslurries higher than that of the bulk wheat by 0.8 to 15.1 • C indicated the selective heating of the insects. The mortalities of adult insects were almost constant within the quarantine period, QP1 (5 wk). The elapsed time during QP1 had a significant effect only on the insects' mortalities with the wheat at 12% MC. The wheat MC had only marginal significance on the absolute mortalities of insects. The larvae were completely destroyed at temperatures between 55 and 60 • C. The complete mortality of all life stages (eggs, larvae, pupae, and adults) of the insect was achieved at T H = 80 • C without any emergence of the insects during QP2 (8 wk). The RF treatment enhanced the germination of the wheat kernels at 12% MC while it was decreased by 2 to 33% depending up on the wheat MC, and the treatment temperature. Temperature had no significant effect on the falling numbers, and the yields of flour, bran, and shorts, and the peak bandwidth and the MC of the wheat, and the flour protein values. The means of the mixing-development-time deferred from the controls mostly for the wheat at 15% MC and T H = 70 • C, and 18% MC and T H = 70 and 80 • C. The mean-peakheight and the color values varied between 4 and 16%, and 3 and 6% off the controls depending up on the temperatures. The uniform temperature of 60 • C should be enough 518Shrestha, Yu, and Baik to control all life stages of the insect completely with a little or no changes in the important product qualities and germination of the wheat at MCs safe for the storage. Future research mainly focused on better estimation of the insect-to-grain electric field intensities is essential.

Thermal death kinetics of adult red flour beetle Tribolium castaneum (Herbst) in canola seeds during radio frequency heating

“…It was attributed to the higher dielectric loss factor of the seeds due to the enhanced conductivity of dipoles and ions in the material, with higher MC causing higher dissipation of electromagnetic energy. [13] In case of the large-volume samples, the temperatures were increased significantly faster after 303 K. The RF exposure time ranged from 25 to 1200 s. The differences between the RF exposure times to attain the same temperature for the small-and large-volume samples ranged from 0.024 to 186 s. The small-and largevolume samples at 5% MC took approximately eight and four times longer RF exposure times than those at 11% MC to reach 353 K, respectively. The regression models for the temperatures (K) of the canola seeds as a function of the RF exposure time (s) at the interested MCs for both the small-and large-volume samples are listed in Table 1.…”

“…The insects were cultured following the procedure adopted by Shrestha et al [13] . In brief, a total of 500 adult insects were reared in a jar (2 L) containing 1.5 kg of a mixture of wheat at MC of 14% and wheat germs in a proportion of 7:3 by weight.…”

“…There were no significant changes in moisture level and milling quality of the rice. Shrestha et al [13] achieved 100% mortality for all the life stages of rusty grain beetles, Cryptolestes ferrugineus (Stephens), in stored wheat at 60°C with RF heating (1.5 kW, 27.12 MHz) without significant degradation of the wheat qualities.…”

Radio-Frequency Applications for Food Processing and Safety

“…Studies have been conducted on inactivation of pests in fish meal (Lagunas-Solar et al 2005), legumes , coffee beans (Pan et al 2012), stored wheat (Shrestha et al 2013), milled rice (Zhou et al 2015), and nuts (Hou et al 2015). Moving, mixing, and hot-air assisted methods were applied to improve the temperature uniformity within the food volume.…”

Exposure of Insects to Radio-Frequency Electromagnetic Fields from 2 to 120 GHz

“…The absorbed dose depends on the frequency 3 , 4 , and can be strongly enhanced when a full-body or partial-body resonance occurs 3 . This RF absorption has already been studied for particular insects at different individual frequencies: 27 MHz 5 , 6 , 900–915 MHz 6 – 8 , and 2450 MHz 9 .…”