Disinfestation of rusty grain beetle (Cryptolestes ferrungineus) in stored wheat grain using 50-ohm radio frequency (RF) heating system
Non-chemical methods were proposed as alternatives for disinfestation of stored grains using fumigants and pesticides. Therefore, this thesis investigated the disinfestation of rusty grain beetle (Cryptolestes ferrungineus) in stored wheat grain using electromagnetic energy from 50-ohm radio frequency (RF) heating system. The objectives of this current study were to update the research outcomes of disinfestation using electromagnetic energy; investigate the installation process of the 50-ohm RF heating system; design and fabricate the parallel plate applicator; determine the mortality of rusty grain beetle; estimate parameters of thermal death kinetics during the RF heating of insects in stored grain; compare the quality of wheat grain before and after RF heating; and determine the heating uniformity in the designed applicator. The review showed that using electromagnetic energy for disinfestation might be possible without degrading the quality of the host materials. RF energy for disinfestation, however, was being preferred over microwave energy for its higher selective heating characteristics. The 100% mortality rates of adult rusty grain beetle were found at all moisture contents of the bulk wheat grain at the end temperatures of 70°C and 80°C. It was observed also that the complete mortalities at all life stages of the insects were achieved at 80°C target temperature at three moisture contents (12%, 15%, and 18%) of the bulk wheat samples. The simulated mortalities based on the model were in good agreement with the experimental mortalities. The determined thermal death kinetic parameters, Ea, K0, and n were 97,490 J/mol, 〖6.74 x 10〗^13 1/s, and 1, respectively. The results showed that disinfestation of insect pests in wheat grain using 50-ohm RF heating did not degrade the quality of the host material significantly. Nevertheless, the RF heating in the applicator was not uniform at all moisture contents and power levels. The temperature differences between the hottest and coldest spots at different MCs and power levels were 38.6°C at 3 kW, 38.7°C at 5 kW, and 39.1°C at 7 kW (12% MC) and 43°C at 3 kW, 43.6°C at 5 kW, and 41.9°C at 7 kW (18% MC). Non-uniform heating in the RF applicator has been a challenge in disinfestation using electromagnetic energy. Thus, suggestions for future studies were provided to solve the problem of heating uniformity in the applicator and the guidelines for a successful installation of 50-ohm RF heating system for disinfestation of insects in stored agricultural materials.
50-ohm radio frequency heating, Radio frequency waves, Disinfestation of insects, Stored grains, Dielectric heating, Radio frequency, Microwave, Electromagnetic energy, Electric field, Milling quality, Baking quality predictors, Germination, Physicochemical properties, Mortality, Thermal death kinetics, Heating uniformity
Master of Science (M.Sc.)
Chemical and Biological Engineering