Microwave is an effective means to deliver energy to food through polymeric package materials, offering potential for developing short‐time in‐package sterilization and pasteurization processes. The complex physics related to microwave propagation and microwave heating require special attention to the design of process systems and development of thermal processes in compliance with regulatory requirements for food safety. This article describes the basic microwave properties relevant to heating uniformity and system design, and provides a historical overview on the development of microwave‐assisted thermal sterilization (MATS) and pasteurization systems in research laboratories and used in food plants. It presents recent activities on the development of 915 MHz single‐mode MATS technology, the procedures leading to regulatory acceptance, and sensory results of the processed products. The article discusses needs for further efforts to bridge remaining knowledge gaps and facilitate transfer of academic research to industrial implementation.

Increasing consumer desire for high quality ready-to-eat foods makes thermal pasteurization important to both food producers and researchers. To be in compliance with the Food Safety Modernization Act (FSMA), food companies seek regulatory and scientific guidelines to ensure that their products are safe. Clearly understanding the regulations for chilled or frozen foods is of fundamental importance to the design of thermal pasteurization processes for vegetables that meet food safety requirements. This article provides an overview of the current regulations and guidelines for pasteurization in the U.S. and in Europe for control of bacterial pathogens. Poorly understood viral pathogens, in terms of their survival in thermal treatments, are an increasing concern for both food safety regulators and scientists. New data on heat resistance of viruses in different foods are summarized. Food quality attributes are sensitive to thermal degradation. A review of thermal kinetics of inactivation of quality-related enzymes in vegetables and the effects of thermal pasteurization on vegetable quality is presented. The review also discusses shelf-life of thermally pasteurized vegetables.

Radio-frequency (RF) heating, as a thermal-processing technology, has been extending its applications in the food industry. Although RF has shown some unique advantages over conventional methods in industrial drying and frozen food thawing, more research is needed to make it applicable for food safety applications because of its complex heating mechanism. This review provides comprehensive information regarding RF-heating history, mechanism, fundamentals, and applications that have already been fully developed or are still under research. The application of mathematical modeling as a useful tool in RF food processing is also reviewed in detail. At the end of the review, we summarize the active research groups in the RF food thermal-processing field, and address the current problems that still need to be overcome.

This paper brings to perspective issues related to research initiatives for the application of microwave (MW) and radiofrequency (RF) applications in foods. Both MW (300 MHz and 300 GHz) and RF waves (3 kHz — 300 MHz) are part of the electromagnetic spectrum that result in heating of dielectric materials by induced molecular vibration as a result of dipole rotation or ionic polarization. They have been credited with volumetric heat generation resulting in rapid heating of foodstuffs. Due to their lower frequency levels, RF waves have a larger penetration depth than MW and hence could find better application in larger size foods. Besides the popular domestic use of MW ovens, commercialized applications of MW/RF heating include blanching, tempering, pasteurization, sterilization, drying, rapid extraction, enhanced reaction kinetics, selective heating, disinfestations, etc. This paper reviews the current status and research needs for in-packaged sterilization technologies for commercial applications. Technological challenges include process equipment design, microbial destruction and enzyme inactivation kinetics, temperature and process monitoring, and achieving of temperature uniformity. Other issues also relate to the use of packaging material in in-package sterilization applications, package/container concerns in domestic MW ovens, receptor technology for creating dry-oven conditions, modeling and time-temperature process integrators. There is also the issue of non-thermal and enhanced thermal effects of microwave heating on destruction kinetics.