Surface sanitation is a critical aspect of food processing to ensure pathogen-free food products and prevent cross-contamination. With food safety being a growing concern globally, the use of ozone for surface sanitation has gained significant attention. Ozone, approved by regulatory bodies such as the FDA and USDA, has witnessed widespread adoption in the past decade due to its effectiveness and safety for direct application on food surfaces.
One of the key challenges in food processing equipment is the buildup of biofilms, which are layers of microorganisms tightly adhered to surfaces. These biofilms can provide protection and nutrients for microbes, making them more resistant to sanitizers over time. Ozone-in-water, or aqueous ozone, has been successfully utilized by many processing plants as an antimicrobial intervention directly on food surfaces. By implementing ozone for surface sanitation, plants can achieve cost savings while ensuring a more efficient and effective sanitization process.
The use of chemicals like chlorine for sanitation poses certain drawbacks. Microorganisms such as E. coli and Giardia can develop resistance to chlorine over time, reducing its efficacy. Additionally, chlorine residuals in wastewater can pose regulatory challenges for water recirculation or discharge. Harsh chemicals also have detrimental effects on equipment made of metals and wood, potentially shortening their lifespan.
In contrast, ozone can be dissolved in water similar to chlorine and other chemicals. Many plants may already have ozone injection systems in place for aqueous ozone applications on food products. Aqueous ozone can be safely sprayed on various surfaces within the plant, including equipment, walls, floors, drains, tanks, tubs, racks, knives, and tables. Enclosed piping can be sanitized using Clean in Place (CIP) systems with ozone.
The sanitation process with ozone generally involves two steps. First, surfaces are cleaned and biofilms are removed using hot water or cleaning agents. Then, aqueous ozone is utilized to sanitize the surfaces, effectively eliminating bacteria, viruses, fungi, and spores. Unlike other sanitizers, ozone leaves no residue on the surface, eliminating the need for additional rinsing steps. This not only saves cleaning time but also reduces water usage costs.
Ozone is a powerful sanitizer that does not leave residual chemicals on equipment or materials. This significantly reduces the corrosive potential of sanitization procedures, ensuring the longevity of metal and wood equipment. Ozone can be used throughout the day during processing without the risk of damaging products, allowing for continuous sanitization and minimizing downtime, thus increasing production hours.
The use of aqueous ozone as a sanitizer has demonstrated effectiveness in various applications within the food processing industry. Its application has yielded positive results in surface sanitation, contributing to improved food safety and reduced risks of foodborne illnesses.
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.
Author: Brian Hampson, PhD
Source: Food Science and Nutrition Dept California Polytechnic State University, San Luis Obispo, CA
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.
Source: The Effectiveness of Ozonated Water for Hard Surface Sanitation, Meat Cuts and Knife Dips-Microbial Kill Results
Inactivation of Vegetative and Sporulated Bacteria by Dry Gaseous Ozone:
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.
Author: Ahlem Mahfoudha, Michel Moisana, Jacynthe Seguinb, Jean Barbeaub, Yassine Kabouzia & Danielle Keroacka
An Evaluation of the Antimicrobial Effects of Gas-Phase Ozone:
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.
The Practical Application of Ozone Gas as an Anti-fungal (Anti-mold) Agent:
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.
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.
Use of Ozone for Winery and Enviromental Sanitation:
Since the early 1900s, ozone has been widely used for water treatment, including disinfection of municipal water supplies, swimming pools, spas, cooling towers, and sewage treatment plants. Recently, ozone has been used in food processing for sanitizing raw materials and irrigation waters, sanitizing packaging materials and storage facilities, and for sanitizing water for recycling.
Prior to 1997, ozone could only be used for sanitation and purification of bottled drinking water in the U.S., and it is widely used around the world for this purpose today. In May 1997, an expert panel assembled by the Electric Power Research Institute (EPRI) declared ozone to be Generally Recognized as Safe (GRAS) for use in food processing in the U.S.
Since then, wineries have embraced the use of ozone. Its use has been generally accepted and documented to be effective for barrel cleaning and sanitation, tank cleaning and sanitation, clean-in-place systems, and for general surface sanitation.
This same trend of acceptance has been noted in many other industries, such as fresh-cut produce processing; produce storage facilities; food processing, including meat processing facilities; and, as noted above, in the bottled water and beverage industries. In these industries, the ozone systems are generally permanently mounted or fixed in place, which makes management of off-gas and ozone monitoring for safety and efficacy relatively easy.
However, in the wine industry, ozone systems tend to be mobile, with multiple operators in multiple locations. This makes it important that safety features and ozone management systems be in place and that the system itself be reliable and easy to operate.
Understanding how ozone works
Ozone, or O3, is generated in nature as a bluish or colorless gas characterized by the clean fresh smell in the air following a thunderstorm. When oxygen (O2) and electricity interact, ozone is created, and this is why we smell ozone around copy machines, electric motors, or during arc welding.
Natural levels range from 0.01 ppm to 0.15 ppm and can reach higher concentrations in urban areas. Ozone is an unstable gas and readily reacts with organic substances. It sanitizes by interacting with microbial membranes and denaturating metabolic enzymes.
Ozone will also attack microbial biofilms and degrade them much as it would any other polysaccharide. Upon release of its oxidizing potential, ozone reverts back to oxygen from which it was generated. Application of ozone does not leave a chemical residual, and under ambient conditions, it has a half-life of 10 to 20 minutes. Thus, ozone must be electrically generated on-demand and cannot be stored for later use.
Ozone is generated by irradiation of an air stream with ultra-violet (UV) light at a wavelength of 185 nm or by passing dry air or oxygen through a corona discharge (CD technology) generator. For low ozone concentrations (ca. 0.14% by weight, or 0.5 grams per hour), the less expensive UV equipment is sufficient. For more demanding situations, where higher ozone concentrations (1.0% to 14% by weight) are required, CD systems are used.
The wine industry is using both CD technology and UV. Some manufacturers use multiple UV tubes to achieve a desired level of output. Several manufacturers chose to install air-cooled or water-cooled CD generators in their systems. It is really a question of how much ozone at a certain gpm is desired for an application. For CIP, 20 gpm may be desired, necessitating a larger system, while only 10 gpm at a lower concentration may provide satisfactory barrel washing.
Using ozone safely
Ozone is a toxic gas and must be monitored in the workplace when in use. However, in almost 100 years of industrial use, there has never been a human death attributed to overexposure to ozone. The Occupational Safety and Health Administration (OSHA) has set limits for ozone exposure in the workplace. These limits are for continuous eight-hour exposure of no more than 0.1 ppm, and a short-term exposure limit (STEL) of 15 minutes at 0.3 ppm, not to be exceeded more than twice per eight-hour work day.
Consequently, ozone requires monitoring in the workplace if used for environmental or equipment sanitation. Ozone monitors are readily available, and the supplier of ozone generating equipment should be able to assist with the selection and use of such monitors.
A manual containing all the relevant safety information for working with ozonating systems is essential; it should also contain operating instructions for the wineryÕs generating system. Workplace monitoring for ozone off-gas must be performed, and records must be maintained to assure OSHA compliance.
When ozone is generated, it is important that the concentration and flow rates be verified, and these should be checked periodically by a technician on some regular schedule or interval (e.g., monthly). All ozone generated should be accounted for, by checking for leaks in the system and by proper destruction of any excess ozone.
If the ozone is being applied as a gas for the fumigation of a storeroom or cellar, monitoring at the far end of the room and feedback control is desirable. If the ozone is dissolved in water and this water is subsequently used for sanitation, there is always some excess ozone that will not be dissolved into solution.
No ozone mass transfer system is 100% efficient. Excess ozone, or entrained ozone gas, must be "de-gassed" or separated from the water stream prior to delivery to equipment or the processing environment. This excess ozone must also be destroyed or decomposed back to oxygen before being released back into the atmosphere. Thermo-catalytic ozone destruct units are small, efficient, and available for this purpose.
It is not enough to just purchase an ozone generator. Your winery must also have maintenance, verification of performance, monitoring, and, especially in the case of mobile ozone units, an in-place systems approach that ensures the safe use of ozone in the workplace. Properly used, these ozone sanitizing systems are much safer than chemical (chlorine and caustics) or heat-based sanitizing systems.
Oxidation of equipment and facilities
One concern is that use of ozone will oxidize equipment and facilities, and this can happen if the materials are incompatible with ozone. Most materials used in food processing are compatible. Stainless steel (e.g., 316L) is corroded less by ozone than by chlorine, and common plastics used in food processing are generally resistant, including ECTFE (Halar®), PTFE (Teflon®), PVDF (Kynar®), PVC (rigid, schedule 80 or 40), and silicon tubing and gaskets. Natural rubber will readily degrade; however FPM (Viton®) and Teflon gaskets are very stable.
When ozone is used in high concentrations, stainless steel, Teflon, and Kynar are the best construction materials. PVC should be avoided under high concentration conditions. In general however, high concentrations (in the low percent range) are only found inside the generator or in the ozone-to-water contacting system. Aside from natural rubber material, brass and copper should also be avoided for concentrations over 1.0 ppm of ozone dissolved in water.
Evaluating ozone sanitation
Recently, in my laboratory at California Polytechnic State University, a study was performed to evaluate ozone's effectiveness as an environmental sanitizer. The fruit and vegetable pilot plant in the university's Food Science and Nutrition Department became the location for the test, and the ozone system used in the study was a DEL Industries model AGW-0500 Surface Sanitizer™. This system is able to deliver an applied dose of 2.0 ppm through a 10 gpm hand-held spray wand, typically delivering a residual (measurable) dose of around 1.5 ppm ozone-in-water solution. Environmental ozone monitoring was performed using an EcoSensor ambient monitor, and concentrations in solution were verified using a Rosemount Analytical dissolved ozone monitor (model 1054B).
Various surfaces in the facility were sprayed with the ozonated water in a back and forth fashion for one minute. The test surfaces included a polished stainless steel mixing kettle and table top, stainless steel shroud, central floor drain, a plastic shipping container, and two locations on the non-slip epoxy-coated concrete floor of the facility (area 1 is high-traffic and area 2 is low-traffic).
Test areas were not cleaned prior to sanitation, so only the effect of the ozone spray wash was measured. Testing was repeated four times, and microbial load of a 100 cm2 area was measured before and after ozone application, using both aerobic plate count (3M APC Petrifilm) and bioluminescence (Biotrace; UniLite UXL 100 Bioluminometer).
The results indicate that ozone applied as a spray wash is effective in reducing microbial load in the processing environment. The drain presented problems during the test because the ozonated water applied to the drain washed throughout the long central drain ditch, which made results inconclusive. A second test on the drain for two minutes of exposure did provide a reduction in microbial load (see Table I).
% Reduction (plate count)
% Reduction (biolum)
Stainless steel (kettle)
89.7 to 98.2
87.6 to 91.8
Stainless steel (table top)
98.9 to 99.7
90.0 to 93.8
Stainless steel (shroud)
63.1 to 99.9
68.8 to 92.2
Floor surface, area 1
67.0 to 95.6
75.2 to 96.1
Floor surface, area 2
84.3 to 99.9
32.8 to 48.8
54.7 to 66.5
Floor drain (2 minutes)
92.9 to 99.4
Plasic shipping container
96.9 to 97.2
68.8 to 97.4
*Due to drainage and sampling problems, results from this location were inconclusive.
One advantage ozone has is its ability to readily oxidize microbes in solution. Thus, once a surface is spray-washed, the microorganisms physically lifted from the surface will be killed as they find their way to a drain. The data above represents one series of tests over a two-week period (evaluations performed approximately every third day). With continued or daily use, it is reasonable to expect that the microbial load will be significantly eliminated at all locations exposed to the ozone. Because ozone requires no storage or special handling or mixing considerations, it may be viewed as advantageous over other chemical sanitizers. Some may consider the fact that ozone leaves no sanitizing residual a disadvantage, but if a residual is desired, there are many other sanitizers available to accomplish that. Ozone can be considered a complimentary sanitizing regime to help maintain the overall cleanliness and sanitation of a winery.
Author: Brian C. Hampwon PhD.
Source: Food Science at California Polytechnic State University, San Luis Obispo, CA
Decontamination of a Multilaminated Aseptic Food Packaging Material and Stainless Steel by Ozone:
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 ofPseudomonas 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.