DIELECTRIC PROPERTIES OF APPLE CULTIVARS AND CODLING MOTH LARVAE

Abstract

Dielectric properties of four apple cultivars and third and fifth instars codling moth (Cydia pomonella) weremeasured between 30 MHz and 3000 MHz at 5C to 55C, using the open-ended coaxial-line probe technique. Dielectricconstant of apples decreased with frequency and decreased slightly with increasing temperature. The dielectric loss factorincreased linearly with temperature in the radio frequency range but was nearly constant at the microwave frequencies.Minimum dielectric loss factor of apples was observed at about 915 MHz. Dielectric constant and loss factor were notinfluenced by cultivar, pulp section or degree of ripeness of apples. Firmness and titratable acidity in apples decreased,while soluble solids content increased significantly due to ripeness. But these properties were not correlated with thedielectric properties. Dielectric constant and loss factor of codling moth larvae followed a similar pattern of variationwith frequency and temperature as for the apples. The dielectric properties of third instars codling moth were higher thanthose of the fifth instars in the radio frequency region. Dielectric constant and loss factor of the insect were much higherthan that of the apples at frequencies lower than 2450 MHz, suggesting that differential heating may be untenable at2450 MHz or higher frequency for codling moth larvae in the apple host.