ABSTRACT
This chapter presents microwave dielectric technology for thermal heating of fruits and vegetables. The main parameter responsible for creating dipoles is water. As microwave or radio frequency waves are applied to food products, the water forms electric dipoles, creating oscillations at very high frequency. Frequency is directly related to penetration rate. At lower frequency, dielectric heat penetrates rapidly. Two frequencies are most commonly used: 915 MHz is used for drying applications at larger scale whereas 2450 MHz frequency is used for household microwave oven and industrial heating The thermal characteristics of foods largely depend on thermal conductivity, density and heat capacity. Food products with high thermal conductivity dissipate heat at a faster rate during microwave heating than the product with lower conductivity. Microwave heating is mostly used for thawing, tempering, dehydration and baking. Other processing techniques such as blanching and pasteurization are lesser successful due to the lower penetration depth in large and irregular food pieces.
