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Efficacy of Ozone
in Killing Listeria monocytogenes on Alfalfa Seeds and
Sprouts and Effects on Sensory Quality of Sprouts
Journal of Food Protection: Vol. 66,
No. 1, pp. 44-51.
W. N. WADE,a, b A. J. SCOUTEN,a, b K. H. McWATTERS,b R. L. WICK,c A.
DEMIRCI,d W. F. FETT,e and L. R. BEUCHATa, b
- Center for Food Safety, University of Georgia, 1109 Experiment Street,
Griffin, Georgia 30223-1797[PARA]
- Department of Food Science and Technology,
University of Georgia, 1109 Experiment Street, Griffin, Georgia
30223-1797[PARA]
- Department of Microbiology, 639 Pleasant Street, Morrill
Science Center IV-N203, University of Massachusetts, Amherst, Massachusetts
01003-9298[PARA]
- Department of Agricultural and Biological Engineering, Life
Sciences Consortium, Pennsylvania State University, University Park,
Pennsylvania 16802[PARA]eU.S. Department of Agriculture, Agricultural
Research Service, Eastern Regional Research Center, Food Intervention and
Technology Research Unit, 600 East Mermaid Lane, Wyndmoor, Pennsylvania
19038, USA
ABSTRACT
A study was done to determine the efficacy of aqueous ozone treatment in killing
Listeria monocytogenes on inoculated alfalfa seeds and sprouts. Reductions in
populations of naturally occurring aerobic microorganisms on sprouts and changes
in the sensory quality of sprouts were also determined. The treatment (10 or 20
min) of seeds in water (4°C) containing an initial concentration of 21.8 ± 0.1
g/ml of ozone failed to cause a significant (P 0.05) reduction in populations of
L. monocytogenes. The continuous sparging of seeds with ozonated water (initial
ozone concentration of 21.3 ± 0.2 g/ml) for 20 min significantly reduced the
population by 1.48 log10 CFU/g. The treatment (2 min) of inoculated alfalfa
sprouts with water containing 5.0 ± 0.5, 9.0 ± 0.5, or 23.2 ± 1.6 g/ml of 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.
Treatments (2 min) with up to 23.3 ± 1.6 g/ml of ozone did not significantly (P
> 0.05) reduce populations of aerobic naturally occurring microorganisms. The
continuous sparging of sprouts with ozonated water for 5 to 20 min caused
significant reductions in L. monocytogenes and natural microbiota compared to
soaking in water (control) but did not enhance the lethality compared to the
sprouts not treated with continuous sparging. The treatment of sprouts with
Ozonated water (20.0 g/ml) for 5 or 10 min caused a significant deterioration in
the sensory quality during subsequent storage at 4°C for 7 to 11 days. Scanning
electron microscopy of uninoculated alfalfa seeds and sprouts showed physical
damage, fungal and bacterial growth, and biofilm formation that provide evidence
of factors contributing to the difficulty of killing microorganisms by treatment
with ozone and other sanitizers.
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