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Application of Ozone for Inactivation of Pathogenic Microorganisms on Alfalfa Seeds and Sprouts
Published by the American Society of Agricultural and Biological Engineers, St. Joseph, Michigan www.asabe.org
Citation: Paper number 026018, 2002 ASAE Annual Meeting . (doi: 10.13031/2013.9716) @2002Authors: Ali Demirci, Ratna R. Sharma, Larry R. Beuchat, William F. Fett
Keywords: Ozonation, E. coli O157:H7, decontamination
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.