In the food industry, an important aspect of the manufacturing process involves cleaning and disinfection of the process equipment. This involves the removal of food or beverage soils from the surfaces followed by disinfection.
Clean in Place (CIP) systems clean the interior surfaces of tanks and pipes by circulating the cleaning and disinfecting solutions through the system. This method eliminates the need to disassemble the equipment prior to cleaning, allows the cleaning process to be automated and does not directly exposed the workers to the cleaning agents.
The CIP process usually includes the following steps: pre-rinse, cleaning, rinse, acid rinse and disinfection. The type of chemicals used and the exact process employed will depend on the properties of the food soils, amount of soil typical left behind after the process and the nature of the surface. It should be noted that these processes often involve large volumes of water.
The primary aspect of the process covered in this paper is sanitation, i.e. the reduction of micro organisms to levels considered safe for public health.
Two methods of disinfection are employed in CIP systems: thermal or chemical. The goal for both is the reduction of micro organism to levels considered safe for public health. For chemical sanitizers, time, concentration and temperature are the most critical factors. Chemical sanitizers are sometimes affected by pH and water quality. The application of chemical disinfection will also depend on the specific organisms being targeted since different organisms respond differently to various chemical agents and concentrations. Typical agents employed include chlorine based chemicals, iodine, quaternary ammonium compounds, acid-anionic sanitizers, fatty acid sanitizers, peroxide type compounds (e.g. PAA) and ozone.
Chemical disinfection in a CIP system takes only 10 to 30 minutes and uses cold water versus hot water for thermal disinfection. The thermal process can take up to 60 minutes to complete. So the advantages of the chemical disinfection versus thermal disinfection process are lowers energy cost and shorter cycle times.
In terms of ozone versus the other sanitizing chemicals, ozone is a broad spectrum biocide that works against virtually all pathogens found in food processing environments. Ozone is generally faster acting versus other agents which means shorter cycle times or lower dosages. The rate of action can be measured as the product of concentration of the disinfectant (C) multiplied by the exposure time at that concentration (t) to achieve a certain reduction in a particular micro organism. This is known as Ct. A faster acting agent will have a lower Ct. This means less agent is needed or the time of exposure can be shortened.
Ozone Ct value of 1.9 for 99.9% reduction of giardia lamblia (3 log reduction) is significantly better than chlorine (Ct=122), chloramine (Ct=2,200) and chlorine dioxide (Ct=26). Ozone's Ct of 1.2 is also superior for a 99.99% reduction of virus (4 log reduction than the same compounds chlorine (Ct=8), chloramine (Ct=1,988) and chlorine dioxide (Ct=33).
As the data show, the Ct values for ozone are anywhere from 6 to 1,000 times better than alternative disinfectants. Unlike other disinfectants, ozone is not significantly affected by pH. Chlorine becomes much less effective as the pH of the solution increases. The FDA also recognizes ozone as an indirect food additive. Because it is very short lived in aqueous solution, half live of about 20 minutes or less, it quickly dissipates on the equipment surface further reducing potential issues with its use.
Ozone is in commercial use for the washing of fruits, vegetables and fish. It is also used for the fumigation of grains and mushrooms. Numerous studies are being carried out to extend its applications to nuts, meat and eggs. The use of ozone will also not create toxic byproducts or leave a residual in the spent wash water. This is because ozone breaks down to oxygen after use. Chlorine based chemicals can form chlorinated organic compounds such as trihalomethanes or haloacetic acids. Both groups have been regulated as possible carcinogens. Since ozone does not form these byproducts and its breakdown product is oxygen, a final rinse may not be needed, reducing total water use in the process.
Another important advantage of ozone is that it is generated on site. Only as much ozone as needed is produced. So, there is no need to purchase or store chemical biocides. In addition, since the machines are built with interlocks to ambient ozone monitors, leaks of ozone result in the immediate shutdown of the machine before the levels reach concentrations of concern. The US Occupational Safety and health Administration sets a limit of 0.1 ppm of ozone for 40 hour per week, 50 week per year exposure. Commercial ambient ozone monitors can detect concentrations below 0.1 ppm. So, the process is inherently safe.
Combining ozone with the CIP process allows for a high degree of automation and quality control in the disinfection step of the process. Ozone generators, as part of an integrated ozone water treatment system, can be paced to deliver the precise amount of ozone required. Data on ozone concentration levels and time of exposure can be tracked for quality control and reporting requirements. The process advantages of using ozone for CIP along with its efficacy in destroying micro organisms should make ozone use increasingly important in the food and beverage industry.