Effect of Microwaves on Food Microorganisms

Over the past few decades, applications of microwave technology have gained popularity for advantages of energy efficiency, food safety and minimal loss of nutrients. In this regard, there is an increasing number of studies in the biochemical field which used microwave radiation to improve food processes. One important issue is to find how electromagnetic energy may influence the inactivation of microorganism. Conventional heating is slow and is generally introduced onto the sample surface. Microwaves can penetrate deeper. There have been reports that microwaves can destroy microorganisms at temperatures lower than the conventional thermal destruction point. Due to the volumetric heat generated by microwaves, this technique can decrease the total heating time and the heat intensity at the required temperature, therefore; microbial destruction may be enhanced while food components may be better protected from the thermal effects. In this context, this chapter reviews important factors for accurately assessing the thermal and non-thermal effects, such as distribution and control of electromagnetic field and temperature, measurement of time-temperature history, sample homogeneity, current theories for non-thermal inactivation of microorganisms (cell membrane changes) and microwave pasteurization and sterilization of foods.