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Radio-Frequency Heating of Alfalfa Seed for Reducing Human Pathogens

Nelson, S. O., Lu, C. Y., Beuchat, L. R., Harrison, M. A.
TRANSACTIONS OF THE ASAE ONLINE 2002 v.45 no.6 pp. 1937-1942
Escherichia coli O157, Listeria monocytogenes, Salmonella, alfalfa, bacterial contamination, dielectric heating, electric field, exposure duration, food contamination, humans, pathogens, population, seed germination, temperature, water content
The problem of bacterial contamination of vegetable seed sprouts produced for human consumption is reviewed briefly. The potential for controlling human bacterial pathogens on alfalfa seed used in the production of sprouts by dielectric heating was studied by experimental exposure of alfalfa seed artificially contaminated with Salmonella, Escherichia coli O157:H7, and Listeria monocytogenes to radio-frequency (RF) dielectric heating treatments at 39 MHz and different electric field intensities for varying times of exposure. Moisture content of alfalfa seed and final temperatures produced by the RF exposures were determined, and control and treated seed samples were analyzed in the laboratory for reduction of bacterial populations and effects on seed germination. Significant reductions in populations of all three pathogens were achieved without reductions in seed germination. However, exposures that provided substantial reductions in pathogen levels were not achieved without significant damage to seed germination. Treatments providing moderate reductions in bacterial pathogen populations also increased alfalfa seed germination through reductions in hard seed percentages, so the combined benefits need to be considered in evaluating dielectric heating treatments for practical use.