M.E. Sosa-Morales

　　Food Engineering Department, División de Ciencias de la Vida, Campus Irapuato-Salamanca, University of Guanajuato, Mexico

　　The use of microwave technology has gained acceptance in the food industry for several types of processes such as heating, thawing, extraction and drying.

　　Pasteurization is still an important process in food technology, due to convenience and relatively lower costs in comparison with other processes. Microwave pasteurization has been studied since 90’s and diverse reports have been published for diverse fluid foods, beginning with batch processing and now with proposals for continuous systems. Some well- defined advantages of using microwaves are recognized, such as shorter treatment times and energy saving. However, the main disadvantage of the microwave heating is still the non-uniform temperature distribution resulting in hot and cold spots in microwave-heated products. This disadvantage is critical when talking of pasteurization and sterilization processes, as bacteria may survive in cold spots, when the target temperature may not be reached during the treatment. In some cases, the objective of pasteurization is enzymatic inactivation, for example, polyphenoloxidase and pectinmethylsterease in juices.

　　Besides the microbiological assurance, nutritional and sensory properties in microwave-pasteurized products must be guaranteed. Juices, vegetable purees, milk, and coconut water has been studied, with good acceptance by panelists and acceptable retention for biocompounds, such as ascorbic acid (vitamin C).

　　The dielectric properties of a particular food item are the basis to select appropriate temperatures and frequency to develop pasteurization processes using microwave heating. Several integrated studies of dielectric properties of fluid foods and the proposed microwave treatments have been reported for peanut beverages, purees and coconut water.

　　In the last years, the industrial application of microwave heating became a reality, with foods in the market processed with this technology, such as the sweet potato product with an FDA filing. More adoption by the food industry is expected in the near future in order to provide better foods for consumers.