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The Case for Ozone
Ozone has re-emerged as an effective, inexpensive food safety tool
by Jim Brandt, MD
In 2000, the Electric Power Research Institute published “Food Industry 2000: Food Processing Opportunities, Challenges, New Technology Applications.” The report contains the following statement: “Ozone destroys bacteria, mold, mildew, spores, yeast and fungus. It inactivates viruses and cysts. Chlorine is not very effective against viruses and has limited effect on some types of bacteria … ozone reacts much faster than chlorine.”
Ozone is a cleaning and a sanitizing agent. Ozone-based systems have been marketed to the food industry for some years but have not gained wide acceptance until recently. The reasons for this lag include inadequate science, ineffective validations, lack of service after purchase, and general skepticism about new technology.
So what has changed? The main thing is the sudden realization that ozone systems can keep a plant clean and sanitized throughout the production day for less money than current modalities. The recent rash of food safety warnings and the resultant recalls have brought financial disaster to affected companies. Ozone systems now operate in many food industries, including seafood, poultry, produce, beef, pork, prepared foods, and water bottling.
Food processors are, by necessity, taking a second look at the new generation of ozone systems and their unequaled ability to maintain plant cleanliness and sanitation throughout a production day. The capacity of ozone as an effective degreaser and sanitizer on conveyor belts during production greatly reduces the risk of cross contamination. Ozone sprays are used continuously on direct food surfaces such as conveyors, knives, slicers, and portioners, assuring their cleanliness throughout production.
Recently, processors have even begun interventional ozone cleaning of indirect surfaces at breaks and shift changes. Ozone’s use during production yields a cleaner plant and decreases the labor time needed for full plant sanitation. Ancillary benefits include reduced energy costs resulting from a large reduction in hot water consumption and chemical cost reductions resulting from lessened chemical usage. Return on investment for direct costs can typically be realized in six to 10 months.
Industry Mea Culpa
The past failures of ozone can largely be traced to the ozone industry itself. The fact that ozone is stronger and acts more quickly than equivalent concentrations of chlorine, coupled with its many cost-saving advantages, seemed to guarantee its rapid adoption. Numerous mom-and-pop operations sprang up, touting ozone as the next generation of sanitizing technology.
Unfortunately, because of ozone’s instability, it cannot be pressurized or heated, which made early ozone systems ineffective. The small companies lacked the funds to keep up with the needed science and to develop the sophisticated systems essential to manufacturing a reliable product for commercialization. Mixing technologies were crude, leading to “off-gassing” problems that raised worker health issues.
Ozone companies knew how to make ozone but knew nothing about the industries they were trying to supply. They didn’t have the funds to develop a competent application engineering capability. Too often, a company would ship an ozone system to a customer, claiming the system could sanitize. The customer was left to implement the system, usually a recipe for disaster. More recently, however, the emergence of several better-funded companies has allowed the industry to address its shortcomings and begin to realize its potential.
Ozone is usually dissolved in water and applied as an aqueous solution. Ozone application to direct contact surfaces is begun prior to the start of production and is continued all during production, keeping surfaces clean and sanitary through the day. It is easier—and obviously more desirable—to keep belts and equipment clean during production than it is to clean them after they are heavily soiled. Ozone systems are also used to augment current cleaning practices, providing the additional sanitation benefits of continuous cleaning.
Because ozone is effective against all known bacteria and their spores, it can readily control ubiquitous pathogens like Listeria and Campylobacter. In some applications, such as produce, seafood, poultry, and ready-to-eat foods, ozone spray is applied directly to the product, resulting in longer shelf life or increased yield.
Many failures in the earlier use of ozone occurred because people in the industry failed to recognize its limitations. Because it is applied at much more dilute concentrations than conventional sanitizers, it is less likely to work with heavy soil (BOD) loads. Dissolved ozone is applied at anywhere from 1/10th to 1/50th the concentration normally used for chlorine sanitizers. Ozone is used at 2 to 5 parts per million (PPM), compared to 50 to 200 PPM for chlorine-based sanitizers.
Early use in poultry chiller applications, for example, failed miserably because a heavy BOD load overwhelmed the limited amount of ozone. A heavy BOD load must first be reduced. On hard surfaces, the ozone spray can be coupled with a high-pressure water stream. Heavy aqueous BOD loads can be addressed with pre-filtration followed by ozonation. While the practice of treating equipment with additional chlorine-based sanitizers does reduce surface bacteria, it does not remove the maturing soils that can develop into a biofilm, providing a receptive medium for rapid new colonization. Continuous ozone sprays prevent these biofilms from forming.
The concept of altering an innocuous oxygen molecule to make it into a potent cleaning and sanitizing agent that then reverts back to simple oxygen is difficult to imagine and has been greeted by a great deal of skepticism. The suggestion that it also has some capacity to degrease, lengthen shelf life, and increase yield turns skepticism into disbelief. The industry hopes education and word of mouth will be the driving force behind a new awareness of ozone’s benefits.
Kryptonite for E. coli?
Despite all this hope, questions remain. How large a role will ozone-based systems play in the future? Will ozone be able to replace chlorine and other chemicals? Real-life experience and research have provided some answers. In response to the Escherichia coli spinach outbreak in the spring of 2007, Fresh Express, a division of Chiquita, awarded $2 million for research on the possible causes and prevention of future E. coli outbreaks.
The results of those studies were released at a seminar held last September in Monterey, Calif. The headline in the San Jose Mercury News the next day read “Ozone Gas May Be E. coli Kryptonite.” According to the article, the research studies found that “ozone gas is faster and more effective than chlorinated water at sanitizing greens.” Seafood.com ran a story the same month reporting that Beaver Street Fisheries had upgraded its sanitation system at Tropic Seafoods, one of the largest lobster plants in the Caribbean, choosing a 100% ozone system and eliminating the use of all chlorine.
Robbins and colleagues at the University of Illinois evaluated ozone’s high degree of effectiveness against Listeria monocytogenes. The study, published in the March 2005 issue of the Journal of Food Protection, showed the wide disparity between the efficacy of ozone and that of chlorine in eliminating Listeria. An ozone concentration of 1 PPM produced an 8.16-log reduction in planktonic cells; a chlorine concentration of 100 PPM produced a 6.49-log reduction after 10 minutes of exposure.
Chlorine-based sanitizers are attractive because they are relatively inexpensive, a quality which will continue to make them valuable in our fight against various pathogens. At the levels allowed during production, however, the cleaning abilities of chlorine sanitizers are significantly limited. The control of ubiquitous agents like Listeria is better achieved through the continuous application of a more powerful sanitizing solution. The application of ozone, with an aqueous concentration that is not regulated because it simply breaks down into pure oxygen, can maintain an almost pre-production level of sanitation throughout the production day. This quality is what makes it so attractive from a food safety standpoint.
A Wake-Up Call
It’s about time for the ozone industry to wake up and develop the science and engineering necessary to make this technology the gold standard for food safety; the food industry must become familiar with ozone’s benefits. The Food and Drug Administration (FDA) approved ozone in June 2001 as an antimicrobial agent on food. According to Seafood.com, “This eliminates a problem with chlorine, the sanitizer still used in most of the food industry, but which can react with organic matter found in water to produce unwanted compounds.”
At Tropic Seafoods, all cleaning and sanitizing chemicals have been eliminated from the processing room. Beaver Street Fisheries says workers use ozone to wash their hands, clean their boots, sanitize the lobster tails, and disinfect the processing area at the end of the day. The new system is also used as an in-process cleaning and sanitizing aid that keeps the tails protected from bacteria throughout the grading and packing process.
Beaver Street says microbiological analysis has revealed a significant improvement over their previous chlorine-based system. The company is also currently undertaking shelf life studies, which have shown ozone-based systems to have a significant impact at other seafood plants.
Despite all its promise, ozone does have limitations. One is its relatively short half-life, which varies depending on conditions like ambient and water temperature. Keeping this potential problem in mind, a company can achieve the best results by applying dissolved ozone at multiple steps along the course of processing, beginning as soon as is practical. Application at a single step along the production trail may be beneficial but is certainly not optimal. The ozone solution is applied to workers’ hands and boots, to all direct and indirect surfaces, and directly to product where applicable. The most dilute solution to achieve the desired microbial reduction—in the 1 to 1.5 PPM range—is used.
Food processors are held to a standard of sanitation. When independent universities, research labs, and members of an industry determine that ozone is more effective than conventional systems in eliminating pathogens, then this becomes the new standard. If it becomes the gold standard, then any company not adopting it as standard operating procedure opens itself to criticism and even potential litigation. When all is said and done, there is no better means than the continual and interventional use of ozone to guarantee a clean production facility throughout the production day.
The question facing the industry is, can it successfully engineer applications in which ozone is the best agent and try not to address applications in which chlorine continues to be the agent of choice—in poultry chillers, for instance? Ozone sanitation has some great advantages over conventional sanitation, but good application engineering is critical. The case for ozone can be made on the basis of increased food safety, energy savings, environmental benefits, worker safety, and return on investment. There is no question that a food safety advancement that is both economical and green is very unique.
Dr. Brandt is chairman of Ozone International, LLC. Reach him at firstname.lastname@example.org or (206) 780-5552.