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Title: EFFICACY OF OZONE IN KILLING LISTERIA MONOCYTOGENES ON ALFALFA SEEDS AND SPROUTS, AND EFFECTS ON SENSORY QUALITY OF SPROUTS

Author
item WADE, W - CTR FOR FOOD SAFETY
item SCOUTEN, K - CTR FOR FOOD SAFETY
item MC WATTERS, R - DEPT OF FOOD SCIENCE
item WICK, R - DEPT OF MICROBIOLOGY
item DEMIRCI, A - DEPT OF AGRIC&BIOLOG ENGR
item FETT, WILLIAM
item BEUCHAT, L - CTR FOR FOOD SAFETY

Submitted to: Journal of Food Protection
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/18/2002
Publication Date: 8/18/2002
Citation: WADE, W.N., SCOUTEN, K.M., MC WATTERS, R.L., WICK, R.L., DEMIRCI, A., FETT, W.F., BEUCHAT, L.R. EFFICACY OF OZONE IN KILLING LISTERIA MONOCYTOGENES ON ALFALFA SEEDS AND SPROUTS, AND EFFECTS ON SENSORY QUALITY OF SPROUTS. JOURNAL OF FOOD PROTECTION. 2002. V. 66 (1). P. 44-51.

Interpretive Summary: In recent years, seed sprouts such as alfalfa, clover and mung bean have been the source of numerous outbreaks of foodborne illness due to contamination with bacterial pathogens. One bacterial pathogen of concern is Listeria monocytogenes. This bacterium is ubiquitous in the environment and sometimes is found in food processing plants. New, highly effective means of eliminating pathogens from sprouting seed and sprouts are required. In this study we tested the use of ozone in water to treat both inoculated alfalfa seed and sprouts. Treating inoculated seed with water into which ozone was continuously supplied for 20 minutes led to a 97% reduction of the pathogen. Treatment of inoculated sprouts with ozone in a similar manner led to less than a 90% reduction of the pathogen. Also, treatment of sprouts with ozonated water led to a reduction of quality upon storage of the treated sprouts at 4 C for 7 to 11 days. Thus, the use of ozone in water alone cannot assure the complete elimination of the pathogen from seeds or sprouts. However, treatment with ozone might be useful as part of a multiple treatment (hurdle) approach for sanitizing seed and sprouts.

Technical Abstract: A study was done to determine the efficacy of aqueous ozone treatment in killing Listeria monocytogenes on inoculated alfalfa seeds and sprouts. Reduction in populations of naturally occurring aerobic microorganisms on sprouts and changes in sensory quality of sprouts were also determined. Treatment (10 or 20 min) of seeds in water (4 deg. C) containing an initial concentration of 21.8±0.1 µg/ml ozone failed to cause a significant (P < 0.05) reduction in population of L. monocytogenes. Continuous sparging of seeds with ozonated water (initial ozone concentration of 21.3±0.2 µg/ml) for 20 min significantly reduced the population by 1.48 log10 CFU/g. Treatment (2 min) of inoculated alfalfa sprouts with water containing 5.0±0.5, 9.0±0.5, or 23.2±1.6 µg/ml ozone resulted in significant (P < 0.05) reductions of 0.78, 0.81, and 0.91 log10 CFU/g, respectively, compared to populations detected on sprouts treated with water. Treatment (2 min) with up to 23.3±1.6 µg/ml ozone did not significantly (P > 0.05) reduce populations of aerobic naturally occurring microorganisms. Continuous sparging of sprouts with ozonated water for 5 - 20 min caused significant reductions in L. monocytogenes and natural microbiota compared to soaking in water (control) but did not enhance lethality compared to treatment of sprouts without continuous sparging. Treatment of sprouts with ozonated water (20.0 µg/ml) for 5 or 10 min caused significant deterioration in sensory quality during subsequent storage at 4 deg. C for 7 - 11 days. Scanning electron microscopy of uninoculated alfalfa seeds and sprouts revealed physical damage and the presence of fungal and bacterial growth and biofilm formation that provide evidence of factors contributing to the difficulty in killing microorganisms by treatment with ozone and other sanitizers.