Welcome to Oxidation Technologies - PH: (515)-635-5854
Author: Joel Leusink
Joel Leusink has been working in the ozone industry since 2003 performing engineering, sales and support for ozone applications in water treatment, agricultural, ground water remediation, and food processing applications.
The International Ozone Association (IOA) publishes a journal called Ozone Science & Engineering. This is a publication issues 6 times per year with great info on many ozone applications.
Ozone: Science & Engineering (OS&E), Vol. 42, Issue 5 is now available online. This new issue contains articles about a variety of ozone applications including a molecular modeling study examining potential mechanisms of ozone to inactivate SarsCov1 COVID virus, sterilization of medical devices, pesticide residue removal, ozone in food storage, contaminant oxidation, textile treatment, and cyanotoxin oxidation.
Ozone gas can be dissolved into liquid with simple bubble diffusers, similar to what is commonly used in the bottom of a fish aquarium for aeration. This is a simple and cost-effective method to dissolve ozone gas into liquid. As ozone is partially soluble into liquid the ozone gas will transfer into liquid immediately at the interface between the ozone gas bubble surface and the surrounding water.
Diffusers implement a gas permeable membrane that will disperse the gas stream into many smaller ozone gas bubbles in the water. As these ozone gas bubbles naturally rise to the surface of the water that ozone will transfer into the water due to contact between the liquid and gas bubble.
Easy to setup
Low energy – does not require water pumps or elevated water pressures
Simple, reliable operation long-term
Generally the least efficient method of dissolving ozone into liquid
Diffusers can become plugged and may require periodic replacement
Difficult to use in pressurized water flows
Ozone gas is partially soluble into liquid. However, using proper methods and equipment high mass transfer efficiencies can be realized with any method of dissolving ozone into water. Review the tips below for success using an ozone gas bubble diffuser in your ozone application.
Fundamentals of ozone solubility:
Lower temperatures increase the solubility rate of ozone gas into liquid
Higher pressures increase the solubility rate of ozone gas into liquid
Higher ozone gas concentrations increase the solubility rate of ozone gas into liquid
Design considerations for your bubble diffuser and column:
Diffuser micron ratings – smaller is better!
Ozone gas bubble diffusers will be rated in micron size, or resulting bubble size the diffuser will create. The membrane that splits the gas stream into small bubbles will have pore sizes, smaller pores will result in smaller bubbles. This pore size or bubble size is normally referred to in a micron rating.
Micron = micrometer. Equal to 0.001 millimeter, or about 0.000039 inch
Smaller bubbles create more surface area of the gas the ozone is flowing in. Greater surface area will increase the ability of ozone gas to transfer into the liquid. See the example below:
The image above shows the same gas volume (1 ft3) shown in one bubble, 8 identical bubbles, and 512 (8 tall x 8 wide x 8 deep) identical bubbles.
One 1 cubic foot sphere = 4.8 ft2 surface area
Eight 0.125 cubic foot spheres = 1 cubic foot = 1.2 ft2 each = 9.66 ft2 total surface area
Eighty 0.0125 cubic foot spheres = 1 cubic foot = 0.26 ft2 each = 20.8 ft2 total surface area
512 0.001953 cubic foot spheres = 1 cubic foot = 0.07567 each = 38.7 ft2 total surface area
A bubble size ¼ the size (4.8 / 4 = 1.2) results in 8x more bubbles and double the overall surface area.
Relating this to your ozone gas flow. A 25 micron diffeser will create bubble sizes ¼ the size of a diffuser rated for 100 micron therefore creating more than 2x the surface area of gas contacting the water at the same flow-rate of gas flowing into water.
Smaller really is better!
Tank design – skinny is better!
Gas bubbles will naturally rise to the surface of water due to buoyancy. Therefore, the taller your tank, column or ozone tank is the longer your gas bubble will remain in the water increasing the opportunity for the gas to transfer into the liquid.
Taller tanks will also increase the water
pressure at the bottom of the tank where the ozone gas diffuser will likely be placed. Greater water pressure will increase the natural solubility of ozone gas into liquid. For example:
11.33 feet of water = 5 PSI
5 PSI = 34% increase in ozone solubility vs 0 PSI
Increasing your water column by 11.33 feet will increase your solubility of ozone, or your mas potential ppm of ozone in water by 34%.
1 ppm becomes 1.34 ppm with no other changes.
A great example of separate columns is shown in the image and dimensions below. Both columns are 3 liters in volume, with a change in diameter from 2” to 4” the height is increased from 12” to 58”
If you have the opportunity when desiring your tank or reactor, choose the smallest diameter possible.
Skinny really is better!
Counter Current Flow
Ozone contacting basins can be designed with counter-current flow, where the water flows counter-current to the gas bubbles. While gas bubbles will naturally rise to the surface of the liquid due to buoyancy liquid can be forced into the path of the gas bubble to create additional turbulence. The diagram below shows a simple contactor basin design using baffles to create counter-current and con-current flows of ozone gas to liquid
This same technique can be applied to any column in flowing water using piping water flowing down a column that ozone gas is rising within. Consider this simple technique when designing your tank or piping system
Ozone dosage =the amount of ozone applied to the water
Dissolved ozone =the amount of ozone measured in the water
Ozone dosage into water does not equal dissolved ozone in water. Ozone is generated as gas and must be dissolved into water in many applications. As ozone is only partially soluble in water mechanical mixing equipment is necessary to dissolve ozone into water efficiently. There are no systems that will achieve 100% mass transfer of ozone gas into water, therefore the dissolved ozone levels will always be lower than the applied ozone, or ozone dosage rate.
Final measured dissolved ozone levels in water will be affected by water quality contamination, water temperature, and the efficiency of your mechanical mixing equipment used to dissolve ozone into water.
To achieve a specific, targeted dissolved ozone level the oxidizable compounds in the water must be overcome along with any other ozone scavenging conditions, also keep in mind the ozone half-life may come into play depending upon the duration of time used to achieve your target dissolved ozone level.
The quantity of ozone you attempt to put into the water will always exceed the amount of ozone actually absorbed into the solution.
Due to the low solubility rate of ozone gas into a liquid and due to system inefficiencies, a portion of the ozone off-gases without being absorbed into the water. This off-gassed ozone must then be vented outside or destroyed with an ozone destruct unit.
The ratio of ozone gas dosage to the final dissolved level is commonly referred to as the mass transfer rate. This refers to the amount of ozone gas that was measured as dissolved vs the ozone dosage rate. This is commonly referred to as a percentage. Such as a 90% mass transfer rate of ozone would indicate that 90% of the ozone dosage, 1ppm for example, would result in 0.9 ppm of ozone measured in water.
Different methods of ozone injection will achieve different dissolved ozone levels into water due to different efficiencies and mass transfer of ozone into water. A few examples of these options are shown in the images below:
There has been a great deal of interest recently in the use of ozone to purify ethanol products to achieve a higher grade of ethanol or alcohol products. We have performed a great deal of bench-testing and pilot testing with companies to assist and achieve these goals. We have found that ozone is very effective at reducing certain undesirable compounds from ethanol along with improving the color and odor of the ethanol.
We thought it might be helpful to assist with promoting this application and the original research that brought this application to light. Right here in Iowa, at the University of Iowa research was done on the purification of Ethanol. See link below and summary for details:
Purification and Quality Enhancement of Fuel Ethanol to Produce Industrial Alcohols with Ozonation and Activated Carbon
The total ethanol production capacity in the US just passed 6 billion gals/year. The production process of ethanol from corn includes corn milling, cooking, enzymatic starch conversion, fermentation and distillation.Food-grade alcohol production requires more care and undergoes costly additional purification to remove volatile organic impurities. These impurities could be of health concern and/or impart unpleasant tastes and odors to beverage alcohol. Multiple distillation steps are usually employed. The additional purification of ethanol to obtain food-grade alcohol adds at least $0.30 per gallon in processing costs. In this research, we tested a novel approach to purify fuel grade ethanol to pharmaceutical and beverage grade. The cost of the proposed treatment process is expected to be less than $0.01 per gallon. We have shown that ozone can oxidize a number of undesirable compounds in ethanol. Furthermore, it was demonstrated that adsorption ongranular activated carbon can remove many of the ozonolysis byproducts. All chemical and sensory analyses were completed using solid phase microextraction (SPME) to extract volatile organic compounds from ethanol samples and a multidimensional GC-MS-Olfactometry system to identify impurities and the impact of odorous compounds. To date, we confirmed a significant reduction of some impurities with ozone alone.Ozone and granular activated carbon are very effective in purifying fuel ethanol. Also, we designed a pure ozone generating setup. This setup can provide further purification efficiency on this research. This technology will help the corn milling and ethanol industry and provide an opportunity for improving the long-term sustainability of corn growing and processing.
If you have any questions on this application, or would like help performing your own testing, please let us know. We would be glad to help.
Researchers at Yale School of Medicine and collaborators have successfully used ozone to disinfect the respirator masks used by healthcare workers to protect against respiratory diseases such as coronavirus disease 2019 (COVID-19).
The development could be used to address a shortage in the availability of this critical piece of personal protective equipment, caused by the COVID-19 crisis.
The authors say that, to their knowledge, their study is the first to report successful disinfection of the masks with ozone and the first to identify the conditions necessary to do so, without damaging mask function.
A preprint version of the paper is available on the server medRxiv*, while the article undergoes peer review.
Supplies of the masks are dwindling
Supplies of the NIOSH-certified N95 filtering facepiece respirators (commonly shortened to“N95 respirators”) have dwindled with the increasing strain placed on healthcare systems due to the COVID-19 pandemic.
This had prompted front-line medical workers to resort to reusing the respirators and experimenting with their own methods of disinfection, which some researchers have described as generally ineffective and damaging to filter performance.
What does the CDC say?
The Centers for Disease Control (CDC) has recognized that the reuse of personal protective equipment such as N95 respirators may be necessary to protect healthcare personnel and to lower the risk of transmitting infection in the workplace.
However, the organization says four essential points must be addressed when considering potential ways to achieve this. The method must be effective at killing the organisms being targeted; must not degrade the function of the equipment; must not introduce new risks to healthcare workers and must be practical in the setting of emergency pandemics such as COVID-19, where resources may be too limited to ensure adequate supplies of the equipment.
Some organizations have described potential protocols, including disinfection with dry heat or using vaporized hydrogen peroxide (VHP) and UV-C light.
Ozone is an appealing option
However, Manning and colleagues were interested in the possibility of disinfecting the respirators with ozone as an alternative for healthcare personnel who may not have access to VHP or other disinfection devices.
The team says that not only is ozone attractive as a potential disinfector because it is a strong oxidant that can deactivate viruses, but it can be generated from air, can quickly be destroyed, and does not leave any residue.
Now, the researchers have tested using ozone to kill Pseudomonas aeruginosa on three types of N95 respirators, namely the 3M 1860, 3M 1870, and 3M 8000.
They point out that P. aeruginosais a bacterium that the CDC has previously referred to as more difficult to kill than viruses such as severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2).
The ozone disinfector the team used
The device comprised an airtight chamber than could generate ozone from ambient air at a concentration of 500 parts per million (ppm). This ozone UV analyzer could accurately determine ozone levels in the chamber and an ozone destruction unit.
The team reports that exposing the respirator to ozone at a concentration of 400ppm at a humidity of 80% over two hours successfully killed bacteria on all three types of respirators.
Furthermore, exposure to ozone at this concentration with a relative humidity of 75-90% at room temperature did not degrade the filtration capability of the 1860 and 1870 type respirators for up to 10 cycles of two-hour treatments.
A practical way to decontaminate the respirators
Manning and colleagues advise that ozone disinfection using the small devices could serve as an effective way to decontaminate N95 respirators, especially in rural areas and in cases where healthcare workers and institutions have no access to large-scale disinfection facilities.
Another great paper has been released for the use of ozone in the medical industry. See below, or click link HERE for original paper.
Wearable and Flexible Ozone Generating System for Treatment of Infected Dermal Wounds
Wound-associated infections are a significant and rising health concern throughout the world owing to aging population, prevalence of diabetes, and obesity. In addition, the rapid increase of life-threatening antibiotic resistant infections has resulted in challenging wound complications with limited choices of effective therapeutics. Recently, topical ozone therapy has shown to be a promising alternative approach for treatment of non-healing and infected wounds by providing strong antibacterial properties while stimulating the local tissue repair and regeneration. However, utilization of ozone as a treatment for infected wounds has been challenging thus far due to the need for large equipment usable only in contained, clinical settings. This work reports on the development of a portable topical ozone therapy system comprised of a flexible and disposable semipermeable dressing connected to a portable and reusable ozone-generating unit via a flexible tube. The dressing consists of a multilayered structure with gradient porosities to achieve uniform ozone distribution. The effective bactericidal properties of the ozone delivery platform were confirmed with two of the most commonly pathogenic bacteria found in wound infections, Pseudomonas aeruginosa and Staphylococcus epidermidis. Furthermore, cytotoxicity tests with human fibroblasts cells indicated no adverse effects on human cells.
Skin and soft tissue infections (SSTIs) are a major health and financial burden for millions of people worldwide. In 2016, SSTIs comprised 3.5% of all emergency room visits (Niska et al., 2016). Furthermore, the average cost of a hospital visit resulting from an SSTI is about $8,000 (SSTI, 2018). These numbers are only expected to rise in the years to come due to the aging population and the increasing prevalence of diabetes associate non-healing wounds and bedsores. To complicate the issue even further, many of these infections can be caused by bacteria that are resistant to common forms of treatment. Infections caused by drug-resistance bacteria have become a significant problem and now affecting over 2 million people in the US each year (Centers for Disease Control and Prevention, 2018). For instance, methicillin-resistant Staphylococcus aurous (MRSA), has been noted to kill more Americans every year than HIV/AIDS, emphysema, or homicide (Federal Bureau of Investigation, 2017; CDC, 2018; Kourtis et al., 2019; Lei et al., 2019). This alarming decrease in antibiotic efficacy has been brought on by a number of factors, but a primary culprit is the commonality of antibiotics usage in society today, especially for inappropriate or unnecessary indications (Ventola, 2015). Simultaneously, major drug companies have reduced the number of antibiotics they are developing. This is mainly due to a significantly reduced return on investment for antibiotic research and development compared to the drugs for chronic conditions such as diabetes, heart disease, and cancer (Ventola, 2015).
Recently, there has been increased effort toward the development of alternative (non-antibiotic) materials and treatments for bacterial infections (Kowalski et al., 1998; Laroussi et al., 2000; Fridman et al., 2005; Fontes et al., 2012; Guan et al., 2013; Korshed et al., 2016). For example, metallic nanoparticles of noble metals such as silver have shown to exhibit antimicrobial properties for a wide range of bacteria and utilized in various advanced wound dressings (Maneerung et al., 2008; Rujitanaroj et al., 2008). Despite having effective antimicrobial activity, many studies have also shown that silver nanoparticles are cytotoxic, and cause damage to cellular components such as DNA and cellular membrane (Korshed et al., 2016). Other materials include polyvinyl-pyrrolidone, a non-ionic synthetic polymer, which allows for gradual release of free iodine with antimicrobial effects. Yet, povidone-iodine and its different complex forms have also been shown to delay wound healing by inhibiting fibroblast aggregation and leukocyte migration (Álvarez-Paino et al., 2017). Free radical and ionized gasses generated by cold atmospheric plasma (CAP) have also shown to be an effective alternative therapeutic tools, providing both antimicrobial properties and help promoting wound healing, and tissue regeneration (through activation of growth factors and stimulation of angiogenesis) (Laroussi et al., 2000; Fridman et al., 2005). Although a promising approach, only a few devices and systems using CAP for wound treatment have been adopted by the patients or their caregivers. One major impediment of their widespread adoption is the system cost and complexity. These devices (e.g., Microplaster from Adtech Ltd) use plasma gun/torch that require high voltages, carrier gas (typically argon) and need to be operated by trained personnel in an outpatient setting. Similarly, smart wound dressings have been developed to help increase wound healing through delivery and sensing of factors such as oxygen, as well as drug delivery and providing optimal wound healing conditions (Gupta et al., 2010; Mostafalu et al., 2015; Ziaie et al., 2018).
Antibiotic resistant infections are a growing public health concern. A promising alternative to antibiotic therapy is utilizing the antimicrobial properties of topical ozone treatments. Developing a portable system designed to apply ozone to a targeted area will increase the options patients have in fighting infections that may otherwise be difficult to treat. In this work, we developed an ozone-releasing wound dressing consist of a disposable gas permeable hydrophobic patch with a reusable and portable ozone-generating unit. The patch incorporated a hydrophobic and highly ozone permeable outer layer and an inner dispersion layer for increased gas distribution uniformity. The antimicrobial effects of the system were tested against common antibiotic resistant strains of bacteria. The results indicated complete elimination of P. aeruginosa and significant reduction in the number of S. epidermidis colonies after 6 h of exposure. These tests also showed a high level of biocompatibility (low cytotoxicity) with human fibroblast cells during the same duration ozone treatment. The described patch is a promising tool in the management of chronic infected wounds.
Scientists have determined that salmon post-smolts tolerate similar levels of ozone in brackish water – which is increasingly used in RAS facilities – as they do in freshwater.
Ozone is a strong oxidant, commonly used for improving water quality and disinfecting pathogens in freshwater fish farms. When ozone reacts with certain constituents of seawater, however, toxic byproducts can severely impact the health of fish populations. As brackish water is increasingly introduced in farming post-smolt salmon, thresholds for the safe use of ozone need to be established. Suppliers of recirculating aquaculture systems (RAS) are looking for safe, cost-efficient and reliable ways to maintain optimal water quality in brackish water RAS, and with this research they are now a step closer.
Scientists from Nofima and The Conservation Fund Freshwater Institute (TCFFI), both central in CtrlAQUA (Centre for research-based innovation), wanted to determine if ozone is safe for salmon in brackish water, and what the safe limits are for post-smolts.
The scientists carried out a trial determining the ozone limit in a flow-through system. Atlantic salmon at 100 grams were reared in brackish water of 12 ppt (parts per thousand) salinity for 12 days. They were exposed to ozone levels of 250 (control), 280 (low), 350 (medium), 425 (high) and 500 (very high) mV (millivolts). They identified ozone levels up to 350mV as potentially safe and 300 mV as safe for the health of post-smolts in flow-through brackish water.
In a follow-up study by Nofima that is not yet published, the identified threshold was confirmed for RAS. Carlo Lazado, fish health researcher in Nofima, will present the results at the digital conference “Smolt production in the future”, on 21 October.
Chris Good, scientist at TCFFI, reports that even lower ozone dosages are sufficient to improve water quality.
“This would depend on the quality of water being treated but in our experience in replicated freshwater RAS, a lower ozone level of 290 mV still resulted in significant improvements to water quality in general, including reduced biochemical oxygen demand and increased UV transmittance,” Good says.
Here is a great open article on the use of ozone in aquaculture.
The most common topic for discussion around workplace water cools is not bacteria. However, there is a certain strain of bacteria that has generated a good amount of press and discussion. The strain of bacteria, E. coli O157:H7 has become popular in the media which cause many people to have a healthy fear of this bacteria.
Escherichia coli (E. coli) is a strain of bacteria that is commonly found in the intestines of animals and humans, and are known to be dangerous and can cause food borne illnesses. The strain of bacteria, E. coli O157:H7 can be life threatening and has resulted in an estimated 2,100 hospitalizations, and is one of the most dangerous strains of E. coli.
Many vegetables, meats and even water supply can contain this strain of E. coli. The biggest cause of infections from E. coli are from food borne illnesses like under cooked ground beef. However, some waterborne illnesses have been found as well. The Canadian town of Walkerton, Ontario had a municipal water supply contaminated by this strain of E. coli in May of 2000. As a result, the pathogen has been blamed for over 2,000 illnesses and 7 deaths.
Solutions to reduce food borne pathogens are becoming very rare. For example, in the past, chlorine has been widely used as a cheap and effective oxidizer to kill a variety of pathogens. However, chlorine is being used less and less as the side effects of the chemical are slowly becoming more apparent. Other chemicals such as methyl bromide, chlorine dioxide, and sodium hypochlorite, that have been used to combat pathogens in the past are also being used less because of the awareness of side-effects.
Ozone is found to be a new, and effective method of antimicrobial intervention. In certain industries such as drinking water, food processing, and surface sanitation, ozone is becoming very popular. Ozone has been proven to be an effective disinfectant against many different pathogens, but studies needed to be conducted in order to prove it was useful against this particular strain of E. coli O157:H7. After research was conducted, it was proven that ozone is effective against this strain of E. coli.
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.
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 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.
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.
Papers on the use of ozone to eliminate E.coli O157:H7
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
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 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
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 (0–360 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
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.
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: firstname.lastname@example.org).
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 pre-ozonated 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.
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, Søltofts 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
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.
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
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 UV-light are good candidates for decontamination of blueberries.
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