Some Biological Effects of Microwave Energy*

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Abstract
Non-thermal effects of microwave energy have been noted in the treatment of various biological materials. Recent data has shown that microwave treatments of microorganisms may Inhibit or kill them by a mechanism distinct from that of thermal means. Spores of Fusarium solani f. phaseoli treated in a water bath show a conventional germination picture, while those treated with microwave germinated on an “all-or-nothing” basis. Molecular resonance and a resultant cleavage is quite common with microwave energy. Viruses and enzymes have been inactivated, and proteins denatured below the customary temperature. Evidence is presented of induced H2O2 formation in 0.1N NaOH solutions with microwave energy but not in a waterbath. A product of potato chip processing, 2-Hexene-l-al was found to be altered as a result of microwave treatments. Included also is an apparent structural change of certain free fatty acids and an inhibition of triglyceride breakdown. Bacterial populations hove been frequently reduced with microwave energy and mesophilic bacteria reduced as much as 99%. Viable spores of various fungal species such as Penicillium, Aspergillus, Rhtzopus have also been reduced. Following microwave exposure, Saccharomyces cerevisiae cells have a reduced rate of respiration when compared to cells heat treated to the same temperature. The respiration in microwave treated cells heated to 56°C was only 0.57 µl O2/min. compared to 2.88 µl O2/min. for cells heated to the same temperature in a water bath. The effectiveness of microwave treatments on microorganisms was found to vary proportional to their size. The mechanisms involved may include cellwall membrane phenomena which may involve a loss in selective permeability.

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