Modeling and analyzing the micowave energy absorption of paddy and mortality assesment of insects

Abstract

In this thesis, dielectric modeling of paddy and insect (R. dominica) was developed to analyze the characteristics for microwave heat treatment to the Malaysian paddy MR219. Electromagnetic fields at lower frequencies (< 1GHz) are of great significance for heating the paddy, because 100% mortality of lesser grain borer, R. dominica (F.) and weevil, S. oryzae may be obtained with minimal losses of rice quality when subjected to the same electromagnetic field. The electromagnetic behavior of the dielectric modeling of paddy and cavity with excitation waveguide was analyzed to simulate the electric field distribution. The temperature dependency of the dielectric properties of R. dominica (F.) and paddy MR219 were analyzed for the frequency range of 200 MHz – 20 GHz and for the temperature range of 240 C – 650 C. The response surface method was used to develop the relationship between the dielectric properties and related factors (i.e., temperature, frequency and moisture) in terms of regional and 3D views. General equations that utilize frequency, temperature and moisture, were developed to describe the dielectric properties. Microwave simulation was used to model the lethal value of R. dominica and S. oryzae in terms of lethal temperature per unit absorbed energy. The proposed dielectric modeling and microwave simulation analysis of bulk paddy in the microwave cavity were validated with the actual microwave heating, thereby confirming the accuracy of this approach in simulating the novel heterogeneous post-harvest bulk paddy inside the microwave cavity. Mortality and energy absorption were analyzed and modeled in terms of increasing temperature. The world-wide interest in reduced pesticide use for secure health and microwave heating is the possible effective means in heat treatments to control insects in post harvest paddy or milled rice. The nutritional results of paddy MR219 showed that the microwave-treated samples are significantly the same as the microwave untreated sample. Sensory qualities and characteristics were not affected by the treatment. In the modeling, standard errors were small and factors (i.e., frequency, temperature or moisture) proved a meaningful addition to this model.