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E.coli 0157:H7 Reduction with Ozone

Table of Contents


Bacteria is not the most common topic for discussion around workplace water coolers. However, in recent years, a specific strain of bacteria has garnered a fair amount of press and discussion. The bacterium strain E.coli O157:H7 has become so popular in the media that most people have a healthy fear of this bacteria.

Escherichia coli (E.coli) is a Gram negative bacterium that is commonly found in the intestines of animals and humans. Specific strains of E.coli are dangerous and can cause food borne illnesses. One of the most dangerous strains of E.coli is O157:H7. This strain of E.coli results in an estimated 2,100 hospitalizations annually in the United States, and can be life threatening.

This strain of E.coli can be found on many vegetables, meats, and even the water supply. Most infections from E.coli O157:57 are caused from food borne illness, mainly undercooked ground beef, however, some have been waterborne. In May of 2000, the municipal water supply of Canadian town Walkerton, Ontario, was contaminated with this pathogen and has been blamed for over 2,000 illnesses and seven (7) deaths.

Antimicrobial interventions to reduce food-borne pathogens are getting harder to find. For example, historically Chlorine has been a low cost and relatively easy to use oxidizer that is effective against a wide variety of pathogens. However, the use of chlorine is becoming more difficult to integrate as the potentially harmful side effects of chlorine are becoming more and more apparent. This is also happening with other antimicrobial interventions such as methyl bromide, chlorine dioxide, and sodium hypochlorite.

A fairly new antimicrobial intervention that is both effective and safe is ozone. The use of ozone is gaining popularity in drinking water, food processing, and surface sanitation. While ozone is effective on a wide variety of pathogens, studies were done to prove that ozone is effective against the deadly strain of E.coli O157:H7. Research has been performed and ozone has proven to be a successful antimicrobial agent in reduction of E.coli O157:H7. We have assembled a few research papers that used ozone on various food products to successfully reduce or eliminate E.coli O157:H7. These can be found HERE.

Implementation of Ozone

Aqueous Ozone


The most common method of using ozone for pathogen reduction is 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.

Ozone levels of 2.0 ppm are commonly used for E.coli O157:H7 reduction. Only a few seconds of contact time of the aqueous ozone with the pathogen is necessary for inactivation. See chart below for details. Reference HERE.


Using this data a determination of spray nozzles, spray bars, or even conveyers can be established. It is clearly shown that 2.0 ppm of aqueous ozone is very effective in only a short period of time, while higher ozone levels show only marginal improvement.

Ozone can also be used in drinking water to inactivate E.coli O157:H7. This has been confirmed by the EPA and recognized as a suitable disinfectant for water. Reference HERE.

Gaseous ozone

The use of gaseous ozone for the elimination of pathogens is less common. There is also 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 E.coli O157:H7, however more research is necessary to determine the effectiveness of ozone within different variables.

Ozone Solutions did perform research on the effect of gaseous ozone on ground beef to inactive E.coli. This research can be found here.

Below is an excerpt from the Direct Food Additive Petition presented to the FDA in August 2000 to achieve GRAS status for the use of ozone to inactivate E.coli O157:h7, along with other pathogens.

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.

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.

Resolution Signers
Dennis Lavelle, President Dell Industries 3428 Bullock Lane San Luis Obispo, CA 93401Charles 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 20005-2605Nari 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 60525Robert 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 22209Jurgen 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 72701Dee 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 33404Frank 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 20005Abit 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 20005Don 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 53706Rip 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 55108-6099Sharon 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 94550Don Dalton U. S. Poultry and Egg Associ 1530 Cooledge Road

Papers About E.coli and Ozone

Utilization of Ozone for the Decontamination of Small Fruits

Published by the American Society of Agricultural and Biological Engineers, St. Joseph, Michigan

Citation: Paper number 056147, 2005 ASAE Annual Meeting . @2005
Authors: Katherine L. Bialka, Ali Demirci
Keywords: E. coli O157:H7, Salmonella, strawberry, gaseous ozone


Each year there are approximately 76 million foodborne illnesses and fresh produce is the second most common vehicle for such illnesses. Small fruits have been implicated in several outbreaks although none have been bacterial. Prior to market small fruits are not washed or treated in any manner so as to extend their shelf life. Washing alone is not a viable option and the use of novel technologies needs to be investigated. One such technology is ozone which has been used to treat drinking water since the late nineteenth century. The efficacy of gaseous ozone to decontaminate pathogens on strawberries, which were used as a model for small fruits, was investigated in this study. Strawberries were artificially contaminated with 5 strains of E. coli O157:H7 and Salmonella. Fruits were treated with 4 ozone treatments; i) continuous ozone flow for 2, 4, 8, 16, 32, and 64 min, ii) pressurized ozone (83 kPa) for 2, 4, 8, 16, 32, and 64 min, iii) continuous ozone (64 min) followed by pressurized ozone (64 min). Maximum reductions of 1.81, 2.32, and 2.96 log10 CFU/g of E. coli O157:H7 were achieved for continuous, pressurized, and continuous followed by pressurized ozone, respectively. For Salmonella reductions of 0.97, 2.18, and 2.60 log10 CFU/g were achieved for continuous, pressurized, and continuous followed by pressurized ozone, respectively. It was concluded that continuous ozone was the least effective treatment, and that there was no significant difference between pressurized ozone treatment and continuous followed by pressurized ozone treatment. These results demonstrate that gaseous ozone has the potential to be used a decontamination method for small fruits. aid=19588&t=2

Effectiveness of ozone for inactivation of Escherichia coli and Bacillus cereus in pistachios

Authors: Meltem Yesilcimen Akbas 1 & Murat Ozdemir 2*

1Department of Biology, Gebze Institute of Technology, PO Box 141, 41400 Gebze, Kocaeli, Turkey
2 Department of Chemical Engineering, Section of Food Technology, Gebze Institute of Technology,
PO Box 141, 41400 Gebze, Kocaeli, Turkey
Correspondence to *Fax: +90 262 653 8490;
Copyright 2005 Institute of Food Science and Technology Trust Fund


The effectiveness of ozone for the decontamination of Escherichia coli and Bacillus cereus in kernels, shelled and ground pistachios was investigated. Pistachios were inoculated with known concentrations of E. coli and B. cereus. Pistachio samples were exposed to gaseous ozone in a chamber at three different concentrations (0.1, 0.5 and 1.0 ppm) for various times (- or + 360 min) at 20 °C and 70% relative humidity. The effectiveness of ozone against E. coli and B. cereus increased with increasing exposure time and ozone concentration. The physico-chemical properties including: pH, free fatty acids and peroxide values, colour and fatty acid composition of pistachios did not change significantly after the ozonation treatments, except for the peroxide value of ground pistachios ozonized at 1.0 ppm for 360 min. Ozone concentration of 1.0 ppm was effective in reducing E. coli and B. cereus counts in kernels and shelled pistachios, while ozone concentrations <1.0 ppm were found to be appropriate in reducing the number of both bacteria in ground pistachios without having any change in their physico- chemical properties.

Application of Ozone for Inactivation of Escherichia coli O157:H7 on Inoculated Alfalfa Sprouts

Journal Of Food Processing And Preservation Research, 27 (2003) 51-64

Authors: Sharma, Demirci, Beuhat, Fett

Interpretive Summary

Alfalfa sprouts contaminated with the bacterial pathogens Salmonella and Escherichia coli O157:H7 have been the source of several foodborne outbreaks in the US and other countries. New, more effective antibacterial treatments are required to ensure the microbial safety of sprouts for the consuming public. In this study, we tested the ability of ozone in water to eliminate E. coli O157:H7 from inoculated alfalfa sprouts. Treatments (from 2 to 64 minutes in durations) with ozone in water (up to 21 ppm) were tested. In some experiments the ozone was continuously fed into the water solution during treatment with or without pressurization. Immersion of sprouts into ozone in water reduced bacterial populations by less than 90%. With continuous feeding of ozone, reductions increased to 99%. The use of pressure during ozone treatments did not increase efficacy. The use of ozone alone will not ensure the microbial safety of sprouts, but ozone in combination with other antibacterial treatments may be able to achieve that goal.

Technical Abstract

Chemical treatments to eliminate pathogens on inoculated sprouts have shown little success. This study investigated the antimicrobial potential of ozone on alfalfa sprouts. Alfalfa sprouts inoculated with a five strain cocktail of Escherichia coli O157:H7 were immersed in water containing 21 ppm ozone for 2, 4, 8, 16, 32, 64 min at 4 C. To increase accessibility of ozone into sprout crevices alternative treatments with continuous ozone sparging with and without pressurization were evaluated. Immersion of inoculated alfalfa sprouts in water containing 21-ppm ozone reduced the population of E. coli O157:H7 by 85.8% at 64 min. There was no significant difference (P > 0.05) between treatment and control and also between different time intervals. Continuous ozone sparging resulted in 85.0 to 99.4% reduction, which was significantly higher (P 0.05) than reduction by sparging with air. Application of low hydrostatic pressure of 12 psi for 5 min subsequent to continuous ozone sparging for 2 - 64 min reduced E. coli O157:H7 populations by 99.0%. Pressurized ozone treatments did not differ significantly from un-pressurized ozone treatments except at 32 min. Ozone treatment did not have any visible detrimental effect on sprouts quality. Further investigation is required to develop methods for ozone introduction for decontaminating sprouts to reduce health risk. However ozone has the potential to replace chemical treatments being used.

Efficacy of Ozone Against Escherichia coli O157:H7 on Apples

Authors: M. Achen and 1 A.E. Yousef 1 Authors are with the Department of Food Science and Technology, The Ohio State University, Parker Hall, 2015Fyffe Rd., Columbus, Ohio 43210. Direct inquiries to author Yousef (E-mail:

This research was supported by a grant from the Ohio Agricultural Research and Development Center. The authors to thank J.G. Kim for his valuable advice and technical support.

Copyright 2001 by the Institute of Food Technologists


Apples were inoculated with Escherichia coli O157:H7 and treated with ozone. Sanitization treatments were more effective when ozone was bubbled during apple washing than by dipping apples in preozonated water. The corresponding decreases in counts of E. coli O157:H7 during 3-min treatments were 3.7 and 2.6 log10 CFU on apple surface, respectively, compared to < 1 log10 CFU decrease in the stem-calyx region in both delivery methods. Optimum conditions for decontamination of whole apples with ozone included a pretreatment with a wetting agent, followed by bubbling ozone for 3 min in the wash water, which decreased the count of E. coli O157:H7 by 3.3 log10CFU/g.


Full Paper: Efficacy of Ozone Against Escherichia coli O157:H7 on Apples

Efficacy of aqueous ozone for the decontamination of Escherichia coli O157:H7 and Salmonella on raspberries and strawberries.

Authors: Bialka KL, Demirci A

Department of Agricultural and Biological Engineering, Pennsylvania State University, University Park, Pennsylvania 16802, USA.
J Food Prot. 2007 May;70(5):1088-92.


The efficacy of ozone as a water additive for washing raspberries and strawberries was investigated. Pathogen-inoculated fruits were treated with aqueous ozone concentrations of 1.7 to 8.9 mg/liter at 20 degrees C for 2 to 64 min, with an aqueous ozone concentration of 21 mg/liter at 4 degrees C for 64 min, or with water as a control. Maximum pathogen reductions on raspberries were 5.6 and 4.5 log CFU/g for Escherichia coli O157:H7 and Salmonella, respectively, at 4 degrees C, whereas reductions on strawberries were 2.9 and 3.3 log CFU/g for E. coli O157:H7 and Salmonella, respectively, at 20 degrees C after 64 min. Washing with water (sparging with air as control) resulted in reductions of approximately 1 log CFU/g. The results presented here indicate that aqueous ozone may be useful as a decontaminant for small fruits.

Inactivation of E. coli O157:H7 in apple cider by ozone at various temperatures and concentrations

Authors: STEENSTRUP Lotte Dock ; FLOROS John D.
Authors' Affiliations: BioCentrum-DTU, Technical University of Denmark, SA Itofts Plods Bldg. 221, 2800 Lyngby, DANEMARK
Department of Food Science, 111 Borland Laboratory, Penn State University, University Park, PA 16802, ETATS-UNIS


The effect of temperature (5-20C) at 860 ppm (v/v) ozone and different gaseous ozone concentrations above 1,000 ppm on inactivation of E. coli O157:H7 in apple cider was studied. Lag times ranged from 3.5 min at 20C to 6.7 min at 10C before the on-set of E. coli O157:H7 inactivation. D-values ranged from 0.6 to 1.5 min at 20C and 5C, respectively. After ozone treatment of cider for 14 min, dissipation of ozone from cider was slow, decreasing to about 5 mg/L after 2 h at 5C. At high gaseous ozone concentration, lag time was shortest and D-value lowest. There was a critical concentration of dissolved ozone of about 5-6 mg/L at 20C, before the on-set of E. coli O157:H7 inactivation in the cider. Total processing times, based on lag time plus 5D, ranged from about 4 to 14 min depending on temperature and ozone concentration. Overall, inactivation of E. coli O157:H7 by ozone was fast enough to allow practical applications in cider production, and it should be considered as an alternative to thermal pasteurization.

Journal Title: Journal of food processing and preservation ISSN 0145-8892 CODEN JFPPDL

Source: 2004, vol. 28, no2, pp. 103-116 [14 page(s) (article)] (1 p.3/4) cpsidt=15974211

Inactivation of Escherichia coli O157:H7 and Natural Microbiota on Spinach Leaves Using Gaseous Ozone during Vacuum Cooling and Simulated Transportation

Authors: Vurma, Mustafa1; Pandit, Ram B.2; Sastry, Sudhir K.2; Yousef, Ahmed E.1
Source: Journal of Food Protection®, Volume 72, Number 7, July 2009 , pp. 1538-1546(9)
Publisher: International Association for Food Protection


The aim of this study was to integrate an ozone-based sanitization step into existing processing practices for fresh produce and to evaluate the efficacy of this step against Escherichia coli O157:H7. Baby spinach inoculated with E. coli O157:H7 (~107 CFU/g) was treated in a pilot-scale system with combinations of vacuum cooling and sanitizing levels of ozone gas (SanVac). The contribution of process variables (ozone concentration, pressure, and treatment time) to lethality was investigated using response-surface methodology. SanVac processes decreased E. coli O157:H7 populations by up to 2.4 log CFU/g. An optimized SanVac process that inactivated 1.8 log CFU/g with no apparent damage to the quality of the spinach had the following parameters: O3 at 1.5 g/kg gas-mix (935 ppm, vol/vol), 10 psig of holding pressure, and 30 min of holding time. In a separate set of experiments, refrigerated spinach was treated with low ozone levels (8 to 16 mg/kg; 5 to 10 ppm, vol/vol) for up to 3 days in a system that simulated sanitization during transportation (SanTrans). The treatment decreased E. coli populations by up to 1.4 log CFU/g, and the optimum process resulted in a 1.0-log inactivation with minimal effect on product quality. In a third group of experiments, freshly harvested unprocessed spinach was inoculated with E. coli O157:H7 and sequentially subjected to optimized SanVac and SanTrans processes. This double treatment inactivated 4.1 to A5.0 log CFU/g, depending on the treatment time. These novel sanitization approaches were effective in considerably reducing the E. coli O157:H7 populations on spinach and should be relatively easy to integrate into existing fresh produce processes and practices.

Decontamination of Escherichia coli O157:H7 and Salmonella enterica on blueberries using ozone and pulsed UV-light

Authors: K L Bialka; A Demirci
Publication Detail: Type: Evaluation Studies; Journal Article: Research Support, Non-U.S. Gov't; Research Support, U.S. Gov't, Non-P.H.S.
Journal Detail:
Title: Journal of food science Volume: 72 ISSN: 1750-3841 ISO Abbreviation: J. Food Sci. Publication Date: 2007 Nov
Created Date: 2007-11-23 Completed Date: 2008-03-24


Efficacy of gaseous ozone, aqueous ozone, and pulsed UV-light was evaluated for the purpose of decontaminating blueberries artificially contaminated with either Escherichia coli O157:H7 or Salmonella. Blueberries were exposed to 4 different gaseous ozone treatments: continuous ozone exposure, pressurized ozone exposure, and 2 combined treatments. Maximum reductions of Salmonella and E. coli O157:H7 after 64-min pressurized or 64-min continuous exposure were 3.0 and 2.2 log 10 CFU/g, respectively. Aqueous ozone experiments were conducted at 20 degrees C and 4 degrees C and zero plate counts were observed for E. coli O157:H7 and Salmonella after 64 min of ozone exposure at 20 degrees C. Finally, pulsed UV-light was evaluated at 3 different distances from the light. Maximum reductions of 4.3 and 2.9 log10 CFU/g were observed at 8 cm from the light after 60 s of treatment for Salmonella and E. coli O157:H7, respectively. A sensory analysis as well as color analysis was performed on blueberries from each treatment agent; neither analysis detected a difference between treated and untreated blueberries. The results presented in this study indicate that ozone and pulsed UV light are good candidates for decontamination of blueberries. Salmonella/18034733.html

Ozone's Effect on E.coli & Bacteria

Last Updated: December 11, 2013

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