Listeria Remediation

Case Study:
Ozone in Food Processing Applications
[PDF - 97 KB]

Listeriosis Remediation

Listeriosis is a serious infection that is typically caused by eating food which has been contaminated with the bacterium Listeria monocytogenes

It's an important public health problem in the United States and Canada.

Although it usually affects people with weakened immune systems, newborns, or older adults, it can sometimes be an issue for people without those risk factors.

Safe handling of food including preparation and storage can often help reduce the risk.

One thing that can lead to contamination of vegetables and fruit, is that Listeria is found in soils.

Undercooked or raw foods are higher risk as well as milk which isn't pasteurized and some ready to eat foods.

Outbreak of Listeriosis, September-October 2011

The Centers for Disease Control and Prevention (CDC) and the Food and Drug Administration (FDA) investigated a multistate outbreak of listeriosis in coordination with state and local health departments, including the Colorado Department of Public Health and EnvironmenT.

A total of 146 persons infected with any of the four outbreak-associated strains of Listeria monocytogenes were reported to CDC from 28 states.

Thirty deaths were reported. In addition, one woman pregnant at the time of illness had a miscarriage.

Available evidence indicates that this outbreak is over. However, Listeria is still an important cause of human illness in the United States. More information about listeriosis and recommendations to reduce the risk of getting listeriosis from food are available at CDC's Listeriosis webpage.

full report.

Some Research

Efficacy of Ozone in Killing Listeria monocytogenes on Alfalfa Seeds and Sprouts and Effects on Sensory Quality of Sprouts

Source: Journal of Food Protection: Vol. 66, No. 1, pp. 44-51.

Authors: W. N. Wade (a, b); A. J. Scouten (a, b); K. H. McWatters (b); R. L. Wick (c); A. Demirci (d); W. F. Fett; 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] U.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


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 (4C) 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 4C 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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