Listeria Inactivation with Ozone

Listeria Inactivation with Ozone

Table of Contents

• Implementation of Ozone
• Resolution Concerning the Use of Ozone in Food Processing
• Compiled Research

Listeria is a common term to refer to a specific strain of bacteria species. There are seven (7) known species of Listeria. The specific species L. monocytogenes is the cause of Listeriosis, a serious infection caused by eating food contaminated with this strain of bacteria. This disease can be deadly and will pose a greater risk to those with weakened immune system. Both L. monocytogenes, and Liseteriosis, are commonly known only as Listeria, and Listeria illness.

Listeria is found in soils, this can lead to fruit and vegetable contamination. Listeria can also be found in all types of meat products, milk, and eggs. Higher risk foods are any uncooked or undercooked foods, unpasteurized milk, raw vegetables, and some ready-to-eat foods.

Click here to learn more about Listeria from the CDC (Center for Disease Control and Prevention).

Ozone can be used for the reduction, or elimination of L. monocytogenes on food products. Since achieving GRAS approval for the use of ozone for direct contact with food in 2001 the use of ozone for the elimination of L. monocytogenes has increased significantly.

To eliminate Listeria or any other bacteria with ozone successful implementation of ozone is necessary. While every application is different, there are a few fundamentals that will apply in most applications.

Implementation of Ozone

Aqueous Ozone

The most common method of using ozone for pathogen reduction is by dissolving ozone into water. Aqueous ozone is very stable, safe, and easy to manage. Typically, ozone is dissolved into water using an Ozone Injection System and then sprayed onto the surface requiring disinfection. This surface may be a hard equipment surface, or the surface of a food product.

In 2000, the Journal of Food Science published a paper by Kim & Yousef showing the effect of dissolved ozone in a batch reactor on Listeria monocytogenes. Dissolved ozone at 0.4 and 0.8 ppm inactivated 4.6 and 5.7 log CFU/ml within 30 seconds. Additional tests were run at higher dissolved ozone levels. Higher dissolved ozone levels did show faster (immediate) inactivation of Listeria monocytogenes.

Dissolved ozone can be sprayed on food and produce using spray bars, or other spraying methods. Conveyers work well to allow the sufficient contact time, and offer full coverage of the aqueous ozone. It is important that all of the produce is contacted by the aqueous ozone to achieve desired antimicrobial intervention. Contact times can be varied by altering conveyer speeds, spray tip design, and spray bar design/quantity. If water is already used in an application to wash produce it is very simple to add ozone to this water and achieve an antimicrobial intervention step without any major changes to the current processes.

Gaseous ozone

The use of gaseous ozone for the elimination of pathogens is less common. There is less research showing the effects of gaseous ozone on bacteria. The application of gaseous ozone is dependent upon the temperature, humidity, contact time, and ozone levels. Research has been conducted to determine that gaseous ozone will reduce and inactivate L. monocytogenes; however, more research is necessary to determine the effectiveness of ozone within different variables.

Produce in need of disinfection can be placed in chambers, rooms, or even cargo containers for ozone treatment. A sealed area that can contain the produce and ozone gas while maintaining human safety will work. It is necessary to assure sufficient air movement past each piece of produce. Ozone levels from 1.0 - 100 ppm are used in this application with contact times from 20 minutes to 10 hours. For more information on the potential of using gaseous ozone in your application contact our application engineers today.

Resolution Concerning the Use of Ozone in Food Processing

Source: Dee Graham, "Ozone as an Antimicrobial Agent for the Treatment, Storage and Processing of Foods in Gas and Aqueous Phases", August 2, 2000.

The Use of Ozone as an effective sanitizer and disinfectant worldwide beginning in France in 1902 and has been documented in an Expert Panel Report entitled "Evaluation of the History and Safety of Ozone in Processing Food for Human Consumption". This Declaration of GRAS Status for Use of Ozone in Food Processing was presented to FDA on April 10, 1997 and published thereafter in the scientific literature and the trade press.

Numerous ozone applications have been installed throughout the food industry in the United States during the past two years. The benefits to public food safety are major, especially related to the food hazards identified in the President's Food Safety Initiative. These include newer pathogens such as E. coli 0157:H7, Listeria, and resistant cyst formers such as Cryptosporidium and Giardia, all of which are inactivated effectively by ozonation.

We urge the responsible Federal Agencies, particularly USDA-FSIS and FDA-CSAN to proactively support the adoption of ozonation for application broadly in food and agriculture as described in the Expert Panel Report Declaration of GRAS Status for ozone on April 10, 1997 and in this Petition.

Resolution Signers
Dennis Lavelle, President Dell Industries 3428 Bullock Lane San Luis Obispo, CA 93401 / Charles D. Sopher, Ph.D. Director, EPRI Food & Agricultural Technology Alliances 2000 L Street, Suite 805 Washington, DC 20036
William P. Roenigk Senior Vice President, National Chicken Council 1015 Fifteen Street, NW — Ste. 930 Washington, DC 20005-2605 / Nari Nayini, Ph.D. Senior Development Associate Food Applications R&D Praxair, Inc. 7000 High Grove Boulevard Burr Ridge, Illinois 60521-7595
James T. C. Yuan, Ph.D. Head, Food & Biochemical Research Air Liquide 5230 South East Avenue Countryside, Illinois 60525 / Robert E. Smith, Ph. D., President R. E. Smith Consulting, Inc. 222-B Eagle Point Road Newport, Vermont 05855
Caleb L. Gilchrist, Ph.D. Director, Scientific Affairs American Meat Institute 1700 North Moore Street, Ste. 1600 Arlington, VA 22209 / Jurgen Strasser, Ph.D., President Process & Equipment Technology 3312 Las Huertas Road Lafayette, CA 94549-5109
Richard Forsythe, Ph.D. Professor Emeritus -- Poultry Science Dept. University of Arkansas Fayetteville, Arkansas 72701 / Dee M. Graham, Ph.D., President R and D Enterprises 2747 Hutchinson Court Walnut Creek, CA 94598
Charles W. Pearsall Vice President RGF Environmental Group 3875 Fiscal Court, Suite 100 West Palm Beach Florida 33404 / Frank Busta, Ph.D. Professor and Emeritus Dept. Head Food Sciences & Nutrition University of Minnesota 1334 Eckles Avenue, Room 258 St. Paul, MN 55108-6099
Barbara Blakistone Senior Specialist Food Chemistry & Packaging Dept. National Food Processors Association. 1350 I Street, NW, Ste. 300 Washington, DC 20005 / Abit Massey Georgia Poultry Federation P. O. Box 763 Gainesville, Georgia 30501
Stuart Proctor, Jr. National Turkey Federation 1225 New York Ave NW-Ste 400 Washington, DC 20005 / Don Dalton U.S. Poultry & Egg Association 1530 Cooledge Road Tucker, GA 30084
Michael W. Pariza, Ph. D. University of Wisconsin -- Madison Food Research Institute 1925 Willow Drive Madison, WI 53706 / Rip G. Rice, Ph. D. President Rice International Consulting Enterprises 1331 Patuxent Drive Ashton, MD 20861
S. R. Tatini, Ph.D. Food Sciences & Nutrition Dept. University of Minnesota 1334 Eckles Avenue St. Paul, MN 55108-6099 / Sharon P. Shoemaker, Ph.D. Executive Director California Institute of Food & Agricultural Research 250 Cruess Hall Davis, CA 94516
Lee C. Ditzler President Novazone 346 Earhart Way Livermore, CA 94550 / Don Dalton U. S. Poultry and Egg Associ 1530 Cooledge Road

Compiled Research

We have assembled some research on the use of ozone specifically for L. monocytogenes. This research is below, we have provided the white paper title, author, and abstract for your review, along with a link to the full paper for your use.

If you have any further questions on the use of ozone for the inactivation of L. monocytogenes, or any other pathogen, please contact our application engineers today.

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

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.

Inactivation of Escherichia coli O1 57:H7, Listeria monocytogenes, and Lactobacillus leichmannii by combinations of ozone and pulsed electric field.

Authors:Unal R , Kim JG , Yousef AE .

Source:J Food Prot. 2001 Jun;64(6):777-82.

Publisher: Department of Food Science and Technology, The Ohio State University, Columbus 43210, USA.

Abstract

Pulsed electric field (PEF) and ozone technologies are nonthermal processing methods with potential applications in the food industry. This research was performed to explore the potential synergy between ozone and PEF treatments against selected foodborne bacteria. Cells of Lactobacillus leichmannii ATCC 4797, Escherichia coli O157:H7 ATCC 35150, and Listeria monocytogenes Scott A were suspended in 0.1% NaCl and treated with ozone, PEF, and ozone plus PEE Cells were treated with 0.25 to 1.00 microg of ozone per ml of cell suspension, PEF at 10 to 30 kV/cm, and selected combinations of ozone and PEF. Synergy between ozone and PEF varied with the treatment level and the bacterium treated. L. leichmannii treated with PEF (20 kV/cm) after exposure to 0.75 and 1.00 microg/ml of ozone was inactivated by 7.1 and 7.2 log10 CFU/ml, respectively; however, ozone at 0.75 and 1.00 microg/ml and PEF at 20 kV/cm inactivated 2.2, 3.6, and 1.3 log10 CFU/ml, respectively. Similarly, ozone at 0.5 and 0.75 microg/ml inactivated 0.5 and 1.8 log10 CFU/ml of E. coli, PEF at 15 kV/cm inactivated 1.8 log10 CFU/ml, and ozone at 0.5 and 0.75 microg/ml followed by PEF (15 kV/cm) inactivated 2.9 and 3.6 log10 CFU/ml, respectively. Populations of L. monocytogenes decreased 0.1, 0.5, 3.0, 3.9, and 0.8 log10 CFU/ml when treated with 0.25, 0.5, 0.75, and 1.0 microg/ml of ozone and PEF (15 kV/cm), respectively; however, when the bacterium was treated with 15 kV/cm, after exposure to 0.25, 0.5, and 0.75 microg/ml of ozone, 1.7, 2.0, and 3.9 log10 CFU/ml were killed, respectively. In conclusion, exposure of L. leichmannii, E. coli, and L. monocytogenes to ozone followed by the PEF treatment showed a synergistic bactericidal effect. This synergy was most apparent with mild doses of ozone against L. leichmannii.

Elimination of Listeria monocytogenes Biofilms by Ozone, Chlorine, and Hydrogen Peroxide

Authors: Robbins Justin B.; Fisher Christopher W.; Moltz Andrew G.; Martin Scott E.

Source:Journal of Food Protection , Volume 68, Number 3, March 2005 , pp. 494-498(5)

Publisher: International Association for Food Protection

Abstract

This study evaluated the efficacy of ozone, chlorine, and hydrogen peroxide to destroy Listeria monocytogenes planktonic cells and biofilms of two test strains, Scott A and 10403S. L. monocytogenes was sensitive to ozone (O3)), chlorine, and hydrogen peroxide (H2O2). Planktonic cells of strain Scott A were completely destroyed by exposure to 0.25 ppm O3) (8.29-log reduction, CFU per milliliter). Ozone's destruction of Scott A increased when the concentration was increased, with complete elimination at 4.00 ppm O3 (8.07-log reduction, CFU per chip). A 16-fold increase in sanitizer concentration was required to destroy biofilm cells of L. monocytogenes versus planktonic cells of strain Scott A. Strain 10403S required an ozone concentration of 1.00 ppm to eliminate planktonic cells (8.16-log reduction, CFU per milliliter). Attached cells of the same strain were eliminated at a concentration of 4.00 ppm O2 (7.47-log reduction, CFU per chip). At 100 ppm chlorine at 20°C, the number of planktonic cells of L. monocytogenes 10403S was reduced by 5.77 log CFU/ml after 5 min of exposure and by 6.49 log CFU/ml after 10 min of exposure. Biofilm cells were reduced by 5.79 log CFU per chip following exposure to 100 ppm chlorine at 20°C for 5 min, with complete elimination (6.27 log CFU per chip) after exposure to 150 ppm at 20°C for 1 min. A 3% H2O2 solution reduced the initial concentration of L. monocytogenes Scott A planktonic cells by 6.0 log CFU/ml after 10 min of exposure at 20°C, and a 3.5% H2O2 solution reduced the planktonic population by 5.4 and 8.7 log CFU/ml (complete elimination) after 5 and 10 min of exposure at 20°C, respectively. Exposure of cells grown as biofilms to 5% H2O2 resulted in a 4.14-log CFU per chip reduction after 10 min of exposure at 20°C and in a 5.58-log CFU per chip reduction (complete elimination) after 15 min of exposure. the potential synergy between ozone and PEF treatments against selected foodborne bacteria. Cells of Lactobacillus leichmannii ATCC 4797, Escherichia coli O157:H7 ATCC 35150, and Listeria monocytogenes Scott A were suspended in 0.1% NaCl and treated with ozone, PEF, and ozone plus PEE Cells were treated with 0.25 to 1.00 microg of ozone per ml of cell suspension, PEF at 10 to 30 kV/cm, and selected combinations of ozone and PEF. Synergy between ozone and PEF varied with the treatment level and the bacterium treated. L. leichmannii treated with PEF (20 kV/cm) after exposure to 0.75 and 1.00 microg/ml of ozone was inactivated by 7.1 and 7.2 log10 CFU/ml, respectively; however, ozone at 0.75 and 1.00 microg/ml and PEF at 20 kV/cm inactivated 2.2, 3.6, and 1.3 log10 CFU/ml, respectively. Similarly, ozone at 0.5 and 0.75 microg/ml inactivated 0.5 and 1.8 log10 CFU/ml of E. coli, PEF at 15 kV/cm inactivated 1.8 log10 CFU/ml, and ozone at 0.5 and 0.75 microg/ml followed by PEF (15 kV/cm) inactivated 2.9 and 3.6 log10 CFU/ml, respectively. Populations of L. monocytogenes decreased 0.1, 0.5, 3.0, 3.9, and 0.8 log10 CFU/ml when treated with 0.25, 0.5, 0.75, and 1.0 microg/ml of ozone and PEF (15 kV/cm), respectively; however, when the bacterium was treated with 15 kV/cm, after exposure to 0.25, 0.5, and 0.75 microg/ml of ozone, 1.7, 2.0, and 3.9 log10 CFU/ml were killed, respectively. In conclusion, exposure of L. leichmannii, E. coli, and L. monocytogenes to ozone followed by the PEF treatment showed a synergistic bactericidal effect. This synergy was most apparent with mild doses of ozone against L. leichmannii.

Effect of Ozone and Ultraviolet Irradiation Treatments on Listeria monocytogenes Populations in Chill Brines

Author: Govindaraj Dev Kumar

Date Created: November 19, 2008

Abstract

The efficacy of ozone and ultraviolet light, used in combination, to inactivate Listeria monocytogenes in fresh (9% NaCl, 91.86% transmittance at 254 nm) and spent chill brines (20.5% NaCl, 0.01% transmittance at 254 nm) was determined. Preliminary studies were conducted to optimize parameters for the ozonation of "fresh" and "spent" brines. These include diffuser design, comparison of kit to standard methods to measure residual ozone, studying the effect of ozone on uridine absorbance and determining presence of residual listericidal activity post ozonation. An ozone diffuser was designed using 3/16 inch PVC tubing for the ozonation of brines. The sparger was designed to facilitate better diffusion and its efficiency was tested. The modified sparger diffused 1.44 ppm of ozone after 30 minutes of ozonation and the solution had an excess of 1 ppm in 10 minutes of ozonating fresh brine solution (200ml). Population levels of L. monocytogenes were determined at various time intervals post-ozonation (0, 10, 20, 60 min) to determine the presence of residual listericidal activity. The population post ozonation (0 minutes) was 5.31 Log CFU/ml and was 5.08 Log CFU/ml after a 60 minute interval. Therefore, residual antimicrobial effect was weak. Accuracy of the Vacu-vial Ozone analysis kit was evaluated by comparing the performance of the kit to the standard indigo colorimetric method for measuring residual ozone. The kit was inaccurate in determining residual ozone levels of spent brines and 1% peptone water. Uridine was evaluated as a UV actinometric tool for brine solutions iii that were ozonated before UV treatment. The absorbance of uridine (A262) decreased after ozonation from 0.1329 to 0.0512 for standard 10 minutes UV exposure duration. Absorbance of uridine was influenced by ozone indicating that the presence of ozone may hamper UV fluence determination accuracy in ozone-treated solutions. Upon completion of diffuser design and ozone/UV analysis studies, the effect of ozone-UV combination on L. monocytogenes in fresh and spent brines was evaluated. Ozonation, when applied for 5 minutes, caused a 5.29 mean Log reduction while 5 minutes of UV exposure resulted in a 1.09 mean Log reduction of L. monocytogenes cells in fresh brines. Ten minutes of ozonation led to a 7.44 mean Log reduction and 10 minutes of UV radiation caused a 1.95 mean Log reduction of Listeria in fresh brine. Spent brines required 60 minutes of ozonation for a 4.97 mean Log reduction in L. monocytogenes counts, while 45 minutes resulted in a 4.04 mean Log reduction. Ten minutes of UV exposure of the spent brines resulted in 0.30 mean Log reduction in Listeria cells. A combination of 60 minutes ozonation and 10 minute UV exposure resulted in an excess of 5 log reduction in cell counts. Ozonation did not cause a sufficient increase in the transmittance of the spent brine to aid UV penetration but resulted in apparent color change as indicated by change in L*a*b* values. Ozonation for sufficient time had considerable listericidal activity in fresh brines and spent brines and when combined with UV treatment, is effective reducing L. monocytogenes to undetectable levels in fresh brines.