Electromagnetic heating, such as microwave and radiofrequency (RF) heating, finds applications in many food processes in industry and at home, including reheating, precooking, cooking, tempering, baking, drying, pasteurization, and sterilization. Electromagnetic heating processes are governed by the material properties called dielectric properties. As microwave heating gains increasing use in food processing systems in industry and in the home, knowledge of dielectric properties becomes increasingly critical for consistent and predictable product, process, and equipment development. In this chapter, dielectric properties are defined, their roles in heating systems are summarized, measurement of the properties is described, and frequency, temperature, and composition

dependence of the properties is discussed for groups of foods from available literature data. Short compilations of data are also provided.