Effects of ozone on bacteria

  1. A healthy bacillus bacterial cell (waiting to ruin your day).
  2. Zooming in closer, an ozone molecule (blue) comes into contact with the cell wall. The cell wall is vital to the bacteria because it ensures the organism can maintain its shape.
  3. As ozone molecules make contact with the cell wall, a reaction called an oxidative burst occurs, creating a tiny hole in the cell wall.
  4. A newly created hole in the cell wall has injured the bacterium.
  5. The bacterium begins to loose its shape while ozone molecules continue creating holes in the cell wall.
  6. After thousands of ozone collisions over only a few seconds, the bacterial wall can no longer maintain its shape and the cell dies.

As a comparison based on 99.99% of bacterial concentration being killed and time taken, ozone is:

    • 25 times more effective than HOCl (Hypochlorous Acid)
    • 2,500 times more effective than OCl (Hypochlorite)
    • 5,000 times more effective than NH2Cl (Chloramine)

Furthermore, ozone is at least ten times stronger than chlorine as a disinfectant. Chlorine reacts with meat forming highly toxic and carcinogenic compounds called THMs or tri-halomethanes – rendering meats lesser quality products. THMs were also implicated as carcinogens related to kidney, bladder, and colon cancers. Chlorine also results in the production of chloroform, carbon tetrachloride, and chloromethane besides THMs. On the other hand, ozone does not leave any trace of residual product after its oxidative reaction.

Ozone Disinfection

Water is disinfected but never completely sterilized in the water treatment process. This disinfection is a two part process that includes:

  • Removal of particulate matter by filtration. A rule of thumb is that high turbidity in the effluent is a potential health risk, because viruses and bacteria can hide within the rough texture of particulates. Therefore, removal of the particulates reduces the chance of pathogenic microorganisms in the effluent. (Refer to Figure 1)
  • Inactivation of pathogenic microorganisms by chlorine, chlorine dioxide, ozone, or other disinfectants: Contact time and kinetics are simply a measure of the inactivation due to time and concentration of the disinfectant. The USEPA has developed regulations for the minimum kill percentages (inactivation) necessary for public water to be considered potable. These regulations include a minimum disinfection of:
    • Three log (99.9%) for Giardia lamblia cysts
    • Four log (99.99%) for enteric viruses


Figure 1: Simplified Diagram of a Pathogen Encapsulated by a Particulate
Courtesy of Eric Karch and David Loftis

In “water treatment terms” 1 log inactivation is referred to as 1 credit inactivation. Different types of filtration are assigned certain removal credits. For example, conventional filtration is worth 2.5 credits for Giardia cysts. Since the EPA requires 3 log (credit) removal, an additional 0.5 credit inactivation from disinfection must be attained.

Varying degrees of disinfection can be attained by altering the type and concentration of disinfectant, as well as the time water is in contact with the disinfectant. The decision to use one type of disinfectant versus another will set the precedence for the remainder of the values needed to attain the proper disinfection. The time untreated water is exposed to the disinfectant and the concentration of that disinfectant are the main factors in the equation that will be discussed in the next section.
Note: the units of contact time are (mg/l)(min).

Relationship Between Kill Efficiency and Contact Time


Figure 2: Graphical Representation of Chick’s Law
From R.C. Hoen’s CE 4104 Spring Notes.

A relationship between kill efficiency and contact time, was developed by Harriet Chick while she was a Fellow in the Pasteur institute in Paris, France. The research yielded data supporting her relationship that is shown in Figure 2. (No) represents the initial number of organisms and N is the number of organisms at time t. As contact time between water and disinfectant increases, the ratio of No/N decreases as Chick’s Law predicts.

Factors Affecting C*t Values

  • As pH increases the value of C*t also needs to be increased. This can be explained by examining the effects of pH on free chlorine. As the pH increases, more of the weak disinfectant (OCl-) exists than the strong disinfectant (HOCl-), thus increasing the C*t value. Refer to Table 1 below.
  • The greater log removal needed, the greater the C*t needs to be, as can be seen in Table 1.

 

Log Removal pH <6 pH 6.5 pH 7.0 pH 7.5
1.0 46 54 65 79
1.5 69 82 98 119
2.0 91 109 130 158
2.5 114 136 163 198

Table 1: C*t for Removal of Giardia Cysts in Relation to Log Removal and pH
Information from the Virginia Department of Health Waterworks Regulations

  • The strength of a disinfectant directly affects the C*t. For a weak disinfectant, the C*t will have to be higher than for a strong disinfectant. As Table 2 below shows, ozone is the strongest disinfectant, thus the C*t value required is less when compared to chlorine and chlorine dioxide.
  • Different organisms have different resistances to disinfectants. If an organism has a strong resistance to a certain disinfectant, the C*t will be higher than for an organism with a weaker resistance. Refer to Table 2 below.

 

Organism Free Chlorine (pH 6-7) Chlorine Dioxide (pH 6-7) Ozone (pH 6-7)
E.Coli 0.034-0.05 0.4-0.75 0.02
Rotavirus 0.01-0.05 0.2-2.1 0.006-0.06
Giardia lamblia cysts 47-150 0.5-0.6
Crytosporidium parvum 7200* 79* 5-10*

Table 2: C*t Values for the 99% Inactivation at 5 Degrees Celsius of Organisms Using Various Disinfectants
* 99% inactivation at 25 degrees C
Hoff, J.C., Inactivation of Microbial Agents by Chemical Disinfectants, EPA/600/2-86/067, 1986

Ozone Effects on Pathogens

Ozone Effects on Specific Bacteria, Viruses and Molds

Bacteria are microscopically small, single-cell creatures having a primitive structure. The bacteria body is sealed by a relatively solid-cell membrane. Ozone interferes with the metabolism of bacterium-cells, most likely through inhibiting and blocking the operation of the enzymatic control system. A sufficient amount of ozone breaks through the cell membrane, and this leads to the destruction of the bacteria.
Viruses are small, independent particles, built of crystals and macromolecules, Unlike bacteria, they multiply only within the host cell. They transform protein of the host cell into proteins of their own. Ozone destroys most viruses by diffusing through the protein coat into the nucleic acid core, resulting in damage of the viral RNA. At higher concentrations, ozone destroys the capsid, or exterior protein shell by oxidation so DNA (deoxyribonucleic acid), or RNA (ribonucleic acid) structures of the microorganism are affected.

* 1 mg/l = 1 PPM

Pathogen

Dosage

Aspergillus Niger (Black Mount) Destroyed by 1.5 to 2 mg/I
Bacillus Bacteria Destroyed by 0.2 m/I within 30 seconds
Bacillus Anthracis Ozone susceptible
Bacillus cereus 99% destruction after 5-min at 0.12 mg/l in water
B. cereus (spores) 99% destruction after 5-min at 2.3 mg/l in water
Bacillus subtilis 90% reduction at 0.10-PPM for 33 minutes
Bacteriophage f2 99.99% destruction at 0.41 mg/l for 10-seconds in water
Botrytis cinerea 3.8 mg/l for 2 minutes
Candida Bacteria Ozone susceptible
Clavibacter michiganense 99.99% destruction at 1.1 mg/l for 5 minutes
Cladosporium 90% reduction at 0.10-PPM for 12.1 minutes
Clostridium Bacteria Ozone susceptible
Clostridium Botulinum (spores) 0.4 to 0.5 mg/l threshold value
Coxsackie Virus A9 95% destruction at 0.035 mg/l for 10-seconds in water
Coxsackie Virus B5 99.99% destruction at 0.4 mg/l for 2.5-minutes in sludge effluent
Diphtheria Pathogen Destroyed by 1.5 to 2 mg/l
Eberth Bacillus (Typhus abdomanalis) Destroyed by 1.5 to 2 mg/l
Echo Virus 29 After a contact time of 1 minute at 1 mg/l of ozone, 99.999% killed.
Enteric virus 95% destruction at 4.1 mg/l for 29 minutes in raw wastewater
Escherichia Coli Bacteria (from feces) Destroyed by 0.2 mg/l within 30 seconds in air
E-coli (in clean water) 99.99% destruction at 0.25 mg/l for 1.6 minutes
E-coli (in wastewater) 99.9% destruction at 2.2 mg/l for 19 minutes
Encephalomyocarditis Virus Destroyed to zero level in less than 30 seconds with 0.1 to 0.8 mg/l.
Endamoebic Cysts Bacteria Ozone susceptible
Enterovirus Virus Destroyed to zero level in less than 30 seconds with 0.1 to 0.8 mg/l.
Fusarium oxysporum f.sp. lycopersici 1.1 mg/l for 10 minutes
Fusarium oxysporum f.sp. melonogea 99.99 % destruction at 1.1 mg/l for 20 minutes
GDVII Virus Destroyed to zero level in less than 30 seconds with 0.1 to 0.8 mg/l.
Hepatitis A virus 99.5% reduction at 0.25 mg/l for 2-seconds in a phosphate buffer
Herpes Virus Destroyed to zero level in less than 30 seconds wit 0.1 to 0.8 mg/l.
Influenza Virus 0.4 to 0.5 mg/l threshold value
Klebs-Loffler Bacillus Destroyed by 1.5 to 2 mg/l
Legionella pneumophila 99.99% destruction at 0.32 mg/l for 20 minutes in distilled water
Luminescent Basidiomycetes (species having no melanin pigment). Destroyed in 10 minutes at 100-PPM
Mucor piriformis 3.8 mg/l for 2 minutes
Mycobacterium avium 99.9% with a CT value of 0.17 in water (scientifically reviewed document)
Mycobacterium foruitum 90% destruction at 0.25 mg/l for 1.6 minutes in water
Penicillium Bacteria Ozone susceptible
Phytophthora parasitica 3.8 mg/l for 2 minutes
Poliomyelitis Virus 99.99% kill with 0.3 to 0.4 mg/l in 3-4 minutes
Poliovirus type 1 99.5% destruction at 0.25 mg/l for 1.6 minutes in water
Proteus Bacteria Very susceptible
Pseudomonas Bacteria Very susceptible
Rhabdovirus virus Destroyed to zero level in less than 30 seconds with 0.1 to 0.8 mg/l
Salmonella Bacteria Very susceptible
Salmonella typhimurium 99.99% destruction at 0.25 mg/l for 1.67 minutes in water
Schistosoma Bacteria Very susceptible
Staph epidermidis 90% reduction at 0.1-ppm for 1.7 min
Staphylococci Destroyed by 1.5 to 2.0 mg/l
Stomatitis Virus Destroyed to zero level in less than 30 seconds with 0.1 to 0.8 mg/l
Streptococcus Bacteria Destroyed by 0.2 mg/l within 30 seconds
Verticillium dahliae 99.99 % destruction at 1.1 mg/l for 20 minutes
Vesicular Virus Destroyed to zero level in less than 30 seconds with 0.1 to 0.8 mg/l
Virbrio Cholera Bacteria Very susceptible
Vicia Faba progeny Ozone causes chromosome aberration and its effect is twice that observed by the action of X-rays

The effect of ozone below a certain critical concentration value is small or zero. Above this level all pathogens are eventually destroyed. This effect is called all-or-none response and the critical level the “threshold value”.

Ozone and E.coli Papers

Ozone is commonly used for the reduction, or elimination of E.coli 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 E.coli has increased significantly. The specific strain of E.coli most frequently targeted is E.coli O157:H7. We have assembled some research on the use of ozone specifically for E.coli O157:H7. 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 E.coli O157:H7, or any other pathogen, please contact our application engineers today.

Utilization of Ozone for the Decontamination of Small Fruits

Published by the American Society of Agricultural and Biological Engineers, St. Joseph, Michigan www.asabe.org Citation: Paper number 056147, 2005 ASAE Annual Meeting . @2005 Authors: Katherine L. Bialka, Ali Demirci Keywords: E. coli O157:H7, Salmonella, strawberry, gaseous ozone Abstract 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.

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

Authors: Meltem Yesilcimen Akbas, Department of Biology, Gebze Institute of Technology, PO Box 141, 41400 Gebze, Kocaeli, Turkey Murat Ozdemir, 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; e-mail: ozdemirm@gyte.edu.tr Copyright 2005 Institute of Food Science and Technology Trust Fund Abstract 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 (+/- “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. Click here for the paper.

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. Click here for the paper.

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: yousef.1@osu.edu). 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 Abstract 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. Click here for the paper.

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. Abstract 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. Click here for the paper.

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, Soltofts Plods Bldg. 221, 2800 Lyngby, DANEMARK Department of Food Science, 111 Borland Laboratory, Penn State University, University Park, PA 16802, ETATS-UNIS Abstract 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)

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

Authors: Vurma, Mustafa(1); 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 Abstract 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 +/-5.0 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. Click here for the paper.

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. 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 Abstract 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 log(10) 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 UVlight are good candidates for decontamination of blueberries. Click here for the paper.

Ozone and Listeria Papers

Listeria and Ozone Papers

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.

Click here for the paper.

 

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.

Click here for the paper.

 

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 O3 (7.47-log reduction, CFU per chip). At 100 ppm chlorine at 20°C, the number of planktonic cells 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.

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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.

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Effectiveness of Ozone in Inactivating Listeria monocytogenes from Milk Samples

Authors: Mariyaselvam Sheelamary, Muthusamy Muthukumar

Affiliations: Division of E

nvironmental Engineering and Technology Department of Environmental Sciences Bharathiar University, Coimbatore, Tamil Nadu, INDIA

Accepted: June, 2011

Publisher: World Journal of Life Sciences and Medical Research 2011;1(3):40-4.

 

Abstract

Inactivation of Listeria monocytogenes using ozonation was studied in raw milk and various branded milk samples in and around Coimbatore city. Total of 20 milk samples were obtained from super markets and other places. The PALCAM agar was used in the study to enumerate L. monocytogenes from raw milk and various branded milk samples. Results indicate that all the samples are positive prior to the ozonation process. A controlled flow rate 0.5 m/l of oxygen was used to produce 0.2g/h of ozone. The milk samples were ozonated at 0, 5, 10, and 15 minutes. After treatment the samples are inoculated and L. monocytogenes were enumerated by using listeria PALCAM agar. After 15 minutes ozonation L. monocytogenes were completely eliminated from milk samples. Before and after ozonation the samples were analyzed for protein, carbohydrate, and calcium content. After treatment the nutritional values were slightly different in the milk samples.

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Inactivation Kinetics of Foodborne Spoilage and Pathogenic Bacteria by Ozone

Authors: J.G. Kim and A.E. Yousef

Keywords: fluorescens, L. mesenteroides, and L. monocytoge

 

Abstract

Ozone was tested against Pseudomonas fluorescens, Escherichia coli O157:H7, Leuconostoc mesenteroides, and Listeria monocytogenes. When kinetic data from a batch reactor were fitted to a dose-response model, a 2-phased linear relationship was observed. A continuous ozone reactor was developed to ensure a uniform exposure of bacterial cells to ozone and a constant concentration of ozone during the treatment. Survivors plots in the continuous system were linear initially, followed by a concave downward pattern. Exposure of bacteria to ozone at 2.5 ppm for 40 s caused 5 to 6 log decrease in count. Resistance of tested bacteria to ozone followed this descending order: E. coli O157:H7, P.

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Influence of Catalase and Superoxide Dismutase on Ozone Inactivation of Listeria monocytogenes

Authors: Christopher W. Fisher, Dongha Lee, Beth-Anne Dodge, Kristen M. Hamman, Justin B. Robbins, and Scott E. Martin

Publication Details: Department of Food Science and Human Nutrition, University of Illinois, Urbana, Illinois. Received 20 September 1999/Accepted 6 January 2000

 

Abstract

The effects of ozone at 0.25, 0.40, and 1.00 ppm on Listeria monocytogenes were evaluated in distilled water and phosphate-buffered saline. Differences in sensitivity to ozone were found to exist among the six strains examined. Greater cell death was found following exposure at lower temperatures. Early stationary-phase cells were less sensitive to ozone than mid-exponential- and late stationary-phase cells. Ozonation at 1.00 ppm of cabbage inoculated with L. monocytogenes effectively inactivated all cells after 5 min. The abilities of in vivo catalase and superoxide dismutase to protect the cells from ozone were also examined. Three listerial test strains were inactivated rapidly upon exposure to ozone. Both catalase and superoxide dismutase were found to protect listerial cells from ozone attack, with superoxide dismutase being more important than catalase in this protection.

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