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Substantial worldwide increase in the occurrence of food poisoning outbreaks related to sprouts has led researchers to investigated chemical and heat treatments to reduce or eliminate pathogens on inoculated seeds and sprouts. However no single treatment has been found to completely eliminate pathogens under experimental conditions. Seeds transmit contamination to sprouts, which are generally consumed raw or slightly cooked, and pose a health risk. Ozone has characteristics like high reactivity, penetratibility, and spontaneous decomposition to non-toxic oxygen that make it attractive for use as a food sanitizer. This study investigated the potential of ozone on alfalfa seeds and sprouts for the decontamination of pathogens.

Alfalfa seeds and sprouts inoculated with a five-strain mixture of Escherichia coli O157:H7 were subjected to different modes of introduction of ozone. Seeds were immersed in water containing 4, 8, 10, and 21 ppm ozone for 2, 4, 8, 16, 32, 64 min at 4C and population reductions ranging between 0.40 1.75 log10 CFU/g were achieved. Immersion of sprouts in water containing 21-ppm ozone for up to 64 min reduced E. coli O157:H7 populations by only 0.85 log10 CFU/g. Alternatively, direct ozone sparging of seeds and sprouts in water, for up to 64 min, reduced E. coli O157:H7 by 2.21 and 2.19 log10 CFU/g respectively. Subsequent exposure of ozone-sparged seeds to heat treatment at 40, 50 and 60C for 3 h gave undetectable populations by direct plating at 60C. To increase accessibility of ozone into the cracks and crevices of seeds and sprouts, direct sparged seeds were subjected to low hydrostatic pressure of 12-psi for 5 min. Approximately 2 log10 CFU/g reduction was achieved. Addition of surfactants during pressure treatment of seeds significantly lowered the reduction levels. Though ozone did not have detrimental effect on seed germination percentage, its effectiveness in killing E. coli O157:H7 on alfalfa seeds and sprouts was less than satisfactory and needs further investigation.