**1. Introduction**

In this chapter an overview of microwave heating as one method of thermal food processing is presented. Due to the limited space, this overview cannot be complete; instead some important theoretical information and also examples of practical uses at home and in industry are shown. This chapter provides a starting point, and the interested reader is directed to the references, where more information about the special themes discussed in this chapter can be found (Dehne, 1999). Additional to the references in the text the interested reader is also referred to two bibliographies that cover more or less all the published work on microwaves (W.H.O, 2012).

### **2. History**

The development of dielectric heating applications in food industry started in the radio frequency range in the 1930s (Püschner, 1966). The desired energy transfer rate enhancement led to an increased frequency: the microwaves. The first patent, describing an industrial conveyor belt microwave system was issued in 1952 (Spencer, 1952), however its first application started 10 years later. This was caused by the need for high power microwave sources to be developed. The first major applications were finish drying of potato chips, pre-cooking of poultry and bacon, tempering of frozen food and drying of pasta (Decareau, 1985). Whereas the first applications were only temporarily successful, since the quality enhancement due to the microwave process could quickly be achieved by a more economic improvement of the conventional technique, the other techniques survived and are still successful in industrial application.

© 2012 Shaheen et al., licensee InTech. This is an open access chapter distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. © 2012 Shaheen et al., licensee InTech. This is a paper distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
