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)

1. Center for Food Safety, University of Georgia, 1109 Experiment Street, Griffin, Georgia 30223-1797[PARA]
2. Department of Food Science and Technology, University of Georgia, 1109 Experiment Street, Griffin, Georgia 30223-1797[PARA]
3. Department of Microbiology, 639 Pleasant Street, Morrill Science Center IV-N203, University of Massachusetts, Amherst, Massachusetts 01003-9298[PARA]
4. d. 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.

http://www.sproutnet.com/Research/efficacy_of_ozone.htm

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.

http://www.ncbi.nlm.nih.gov/pubmed/11403125

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 o 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.

http://www.ncbi.nlm.nih.gov/pubmed/15771172

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.

Click here for the paper.

Effectiveness of Ozone in Inactivating Listeria monocytogenes from Milk Samples

Authors: Mariyaselvam Sheelamary, Muthusamy Muthukumar

Affiliations: Division of Environmental 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.

For more Listeria information see this page on our website here

Ozone use for Surface Sanitation

Original page HERE

Food safety is a growing concern worldwide. The CDC (Center for Disease Control and Prevention) estimates that each year one (1) in six (6) Americans get sick from food borne diseases. As illnesses, hospitalizations, and deaths are made more public by the media this is a constant concern for food processors.

In food processing it is important to provide pathogen free food products. Keeping food products pathogen free and reducing the potential for cross-contamination of potentially deadly pathogens is very crucial, and that is why surface sanitation is so important. This page will provide some detail on the potential use of ozone for surface sanitation.

Many processing plants already use ozone-in-water, or aqueous ozone for antimicrobial intervention steps directly on the surface of food products. Due to the FDA and USDA giving ozone GRAS approval for use directly on the surface of all food products the use of ozone has spread dramatically in the last 10 years. Ozone use for surface sanitation is just one more cost saving method that can be implemented by plants already using ozone, or for plants that would like lower cost and have a more effective method for surface sanitation.

One of the major concerns for cross-contamination on food processing equipment is bio-film buildup. Bio-films are layers of microorganisms bonded tightly to a surface. Microbes can attach themselves to a surface and continue to grow layer upon layer of new microbes. The new layer of microbes can provide nutrients and protection against sanitizers to the existing layers of microbes. These layers of microbes can continue to grow, and become more resistant to sanitizers over time making sanitation more difficult if proper sanitation is not achieved on a regular basis. These resistant bio-films are most common in cracks, crevices, and corners of food processing equipment that are only sanitized periodically.

How does ozone kill bacteria

Chemical Drawbacks

A common sanitizer in the food processing industry is chlorine. Chlorine is mixed with water providing chlorinated water to be used as a sanitizer. Some microorganisms such as E.coli and Giardia can build resistance to chlorine over time. This may make chlorine less effective than desired over time. Chlorine residual in waste water can also be regulated and make water recirculation or discharge more difficult due to chlorine residuals in the water.

One more drawback to chlorine and other chemicals is the harsh effect they may have on equipment made of metals and wood. Common issues are steel components that chlorinated water is constantly exposed to, shortening the life of potentially expensive equipment. Wooden wine barrels are also damaged by harsh chemicals. Winemakers take special care to choose high quality wooden barrels to age wine within, this wood can be damaged or altered to the point it no longer serves the original purpose.

Ozone-in-water Application

Ozone can be dissolved into water just as chlorine and other chemicals can be. In many plants ozone injection systems that provided aqueous ozone may already be in place for use on food products for anti-microbial intervention. Aqueous ozone can be sprayed anyway within the plant safely. Equipment, walls, floors, drains, tanks, tubs, racks, knives, and tables can all be sprayed with aqueous ozone. Enclosed piping can also be sanitized with ozone using a Clean in Place (CIP) system.

During sanitation with ozone a two-step process is generally required. Surfaces are cleaned and bio-films are removed with a hot water or cleaning step. Then aqueous ozone is used to sanitize the surface destroying all bacteria, viruses, fungi, and spores. No other sanitation step after the use of ozone is necessary. In fact no rinse step is necessary after ozone as the ozone will leave no residual on the surface. This may lower cleaning time and water usage costs.

Ozone is a powerful sanitizer that leaves no residual on the surface of equipment or materials. This limits the corrosive potential of ozone and provides a more gentle sanitizer than many of the common chemicals used. Ozone will provide great sanitation results without the harmful effects on metal or wood equipment.

Ozone can be used throughout the day during processing. As there is no danger in damaging product with harsh chemicals, ozone can be used to sanitize processing equipment throughout the day during normal processing. This may lower down time, and allow for more production hours.

Results with the use of ozone-in-water

Aqueous ozone has proven an effective sanitizer in many applications throughout the food processing industry.

Below are few examples of result obtained.

Ozone tests at fruit and vegetable pilot plant

Tests conducted in 1999 by Polytechnic State University at a pilot plant showed the effectiveness of ozone in reducing microbiological loading. The Ozone System in use provided a 2.0 ppm dissolved ozone level that was sprayed on the surfaces to be sanitized. No other cleaning methods were used with the ozone to ensure all reductions in bacteria were attributed to the aqueous ozone. The table below shows the results from this test.

Ref: Use of ozone for winery and environmental sanitation
By Brian Hampson, PhD, Food Science and Nutrition Dept
California Polytechnic State University, San Luis Obispo, CA
http://www.practicalwinery.com/janfeb00/ozone.htm

Results from tests at a Fortune 50 Pork Processing Company

Tests were performed at a Fortune 50 Pork Processing Company to determine the effectiveness of aqueous ozone for sanitation of hard surfaces, meat cuts, and knife dips. These tests were performed in a working plant in normal working environments. Samples were sprayed with aqueous ozone ranging from 1.1 – 1.4 ppm for about 10-15 seconds. All tests compared microbiological counts on samples before and after ozone, ozone vs 180-deg F water, and ozone vs 180-deg F water and cold water.

In these tests, ozone performed very well as a sanitizer. Ozone showed a consistent reduction in microbial loading on each material tested. In all tests ozone performed at an acceptable level for sanitation. In many tests ozone outperformed 180-deg F water. As these tests were performed in real world environments with fairly conservative ozone levels (1.1 – 1.4 ppm) these results are very realistic and show the potential for ozone use as a surface sanitizer.

Results from tests at a Fortune Fifty Pork Processing Plant 4/09/02. The Effectiveness of Ozonated Water for Hard Surface Sanitation, Meat Cuts and Knife Dips-Microbial Kill Results http://www.ozonesafefood.com/Ozone_Report_1.pdf

White Paper Abstract

Decontamination of a Multilaminated Aseptic Food Packaging Material and Stainless Steel by Ozone

Authors: Mohammed A. Khadre, Ahmed E. Yousef

Abstract

A multilaminated aseptic food packaging material and stainless steel were treated with ozone to inactivate natural contaminants, bacterial biofilms and dried films of Bacillus subtilis spores and|| ||Pseudomonas fluorescens. Sterility of the multilaminated packaging material was achieved when 1.0 x 2.0 cm-pieces of the naturally-contaminated material were treated with ozone in water (5.9 µg/mL) for 1 min. Dried films of spores (108/6.3-cm² surface) were eliminated by 13 µg/mL of ozone in water for the multilaminated packaging material and 8 µg/mL in case of the stainless steel. Ozone inactivated Pseudomonas fluorescens in biofilms more effectively on stainless steel than on the multilaminated packaging material. Repeated exposure to ozone of Pseudomonas fluorescens in biofilms on the multilaminated packaging material eliminated up to 108 cfu/12.5 cm². In conclusion, ozone is an effective sanitizer with potential applications in the decontamination of packaging materials and equipment food-contact surfaces.

Click here for the abstract

Studies on the disenfection and removal of biofilms by ozone water using an artificial microbial biofilm system http://www.tandfonline.com/doi/abs/10.1080/01919510802586566

Gaseous Ozone Applications

Ozone can also be used in the gaseous form to disinfect and sanitize areas. While actual bio-films will not be removed with gaseous ozone, there are applications where this may be a suitable solution. Many applications do not allow for water to penetrate locations where bacteria may reside and cause future cross-contamination. Gaseous ozone has been used for many years for odor control, mold remediation, and other disaster restoration services. The same action used to remove odor and mold spores can be used to kill bacteria and mold in industrial settings.

Results from gaseous ozone applications

The use of gaseous ozone has been tested in various forms for many applications. A wide variety of applications from hospital rooms to sports gear, such as hockey equipment, have used gaseous ozone for disinfection. When using aqueous ozone for surface sanitation the two main variables that affect the success of ozone are contact time and ozone levels. When using gaseous ozone a new variable, humidity, will dramatically affect the results. The level of humidity in the environment will affect the ability of ozone to penetrate and destroy microorganisms. The following research will show a new variable affecting the results of microbiological reduction with ozone.

Results from study on ozone use for surface disinfection

This study investigated the potential of gaseous ozone to inhibit growth of microorganisms on surfaces. This study evaluated the effectiveness of ozone at varying ozone concentrations, for various contact times, at varying relative humidity.

The effect of ozone on Apergillus niger, Pseudomonas aeruginosa, and a mix of microorganisms was tested. Highly contaminated surfaces were exposed to ozone gas at various levels ranging from 0.1 to 5,000 ppm in these tests. Exposure times from 20 minutes to 120 minutes were used at low ozone levels, while exposure times of 0.33 minutes to 20 minutes were used at 5,000 ppm. Humidity showed a great affect on the reduction of bacteria in the presence of ozone gas. Altering the humidity level from 15-25% to 85-95% showed a greater change in bacterial reduction than altering the ozone level in some tests.

http://www.rentforum.se/Prod/Rentforum/sajt.nsf/wwwpages/10D011244DA8DAC6C1256D5B0042A28E/$File/ICCCS%20Ozone%20article.pdf

White Paper Abstracts

Inactivation of Vegetative and Sporulated Bacteria by Dry Gaseous Ozone

Ozone: Science & Engineering, Volume 32, Issue 3, 2010, pages 180-198

Authors: Ahlem Mahfoudh, Michel Moisan, Jacynthe Séguin, Jean Barbeau, Yassine Kabouzi & Danielle Kéroack

Abstract

Inactivation by gaseous ozone of different types of microorganisms is successfully achieved provided, as is well known, the gaseous phase is strongly humidified. The inactivation mechanisms and species involved in this process are, however, not yet clearly identified. To gain insight, we considered exposure of bacterial spores to dry rather than humidified ozone, a less complex chemical environment. In contrast to most of the published literature, it is shown that, under strict dry ozone conditions, bacterial spores can be inactivated, but to a degree that is largely dependent on the spore type and substrate material. In this case, the O₃ molecule is determined to be responsible for the inactivation process through its diffusion into and oxidative action within the spore, as no outer erosion of the spore is detected. With humidified ozone, a higher inactivation efficiency is observed that is most probably related, in part, to the swelling of the spore, which facilitates the diffusion of oxidative species within it and up to the core; besides O₃, these oxidative agents stem from the interaction of O₃ with H₂O, which in the end leads to a heavily damaged spore structure, in contrast to dry-ozone exposure where the spore integrity is maintained.

http://www.tandfonline.com/doi/abs/10.1080/01919511003791971

An Evaluation of the Antimicrobial Effects of Gas-Phase Ozone

Ozone: Science & Engineering, Volume 31, Issue 4, 2009, pages 316-325

Authors: M.Y. Menetrez, K.K. Foarde, T.D. Schwartz, T.R. Dean & D.A. Betancourt

Abstract

This project evaluated the effects of exposing a variety of microorganisms on porous and non-porous materials to elevated gaseous ozone concentrations ranging from 100 – 1000 ppm. Gypsum wallboard (porous) and glass slide (non-porous) building materials were used. Two fungi organisms, two bacteria organisms and two levels of relative humidity (RH) were tested. Increased humidity and non-porous surface exposure were found to increase the biocidal capability of high levels of ozone. The results of this study indicate that even at relatively high concentrations of ozone, it is difficult to get significant reductions of microorganisms on surfaces, especially on porous materials.

http://www.tandfonline.com/doi/abs/10.1080/01919510903043772

The Practical Application of Ozone Gas as an Anti-fungal (Anti-mold) Agent

Ozone: Science & Engineering, Volume 31, Issue 4, 2009, pages 326-332

James B. Hudson & Manju Sharma

Abstract

We evaluated the ability of a portable ozone generating machine (Viroforce 1000) to inactivate 13 different species of environmental fungi. Samples, prepared as wet or dried films, were subjected to one or two cycles of treatment (35 ppm ozone for 20 minutes, with a short burst of >90% relative humidity), and measured for residual viability. Treatments could inactivate 3 log10 cfu (colony forming units) of most of the fungi, both in the laboratory and in simulated field conditions, on various surfaces. We conclude that the ozone generator would be a valuable decontamination tool for mold removal in buildings.

http://www.tandfonline.com/doi/abs/10.1080/01919510903043996

Conclusion

Ozone has a bright future in surface sanitation. The use of ozone for surface sanitation in process using aqueous ozone, CIP, and gaseous ozone will continue to grow. If you have an application that you would like to evaluate the potential of ozone, give us a call. We would be glad to discuss your application and provide the technical support necessary to implement ozone as a solution.