Chapter 8 - Advanced Heating Technologies for Food Processing

Abstract

This chapter explores three volumetric heating methods, ohmic, microwave, and radio frequency and their application in food processing. The principles are described with ohmic relying on the electrical conductivity of the food and consequent joule heating, with microwave/radio frequency (RF) relying on dipolar and charge movement loss mechanisms in the product. Frequencies, methods of application, benefits, characteristics, and drawbacks are described. A comparison is made with conventional heating. Applicators and machine configurations used in industry and common applications are described. Safety issues are briefly covered. Some emerging and novel applications are identified which draw on the volumetric nature of the heating. A comparison of the methods and an overview of opportunities are presented. Ohmic heating is the least costly option and the most energy efficient but requires careful design if it is to cater for a wide range of products. Microwave heating is a general purpose and widely applicable but can suffer from nonuniformity of heating. RF can achieve more uniform heating but is more specialized in application and usually more costly. Sometimes all three are feasible and evaluation testing and judgment may be needed to choose which will work best.