E. coli Reduction with Ozone

Bacteria is not the most common topic for discussion around workplace water coolers. However, in recent years, a specific strain of bacteria has garnered a fair amount of press and discussion. The bacterium strain E.coliO157:H7 has become so popular in the media that most people have a healthy fear of this bacteria.

Escherichia coli (E.coli) is a Gram negative bacterium that is commonly found in the intestines of animals and humans. Specific strains of E.coli are dangerous and can cause food borne illnesses. One of the most dangerous strains of E.coli is O157:H7. This strain of E.coli results in an estimated 2,100 hospitalizations annually in the United States and can be life threatening.

This strain of E.coli can be found on many vegetables, meats and even the water supply. Most infections from E.coli O157:57 are caused from food borne illness, mainly undercooked ground beef. However, some have been waterborne. In May of 2000, the municipal water supply of Canadian town Walkerton, Ontario; was contaminated with this pathogen and has been blamed for over 2,000 illnesses and seven (7) deaths.

Antimicrobial interventions to reduce food-borne pathogens are getting harder to find. For example, historically chlorine has been a low cost and relatively easy-to-use oxidizer that is effective against a wide variety of pathogens. However, the use of chlorine is becoming more difficult to integrate as the potentially harmful side effects of chlorine are becoming more and more apparent. This is also happening with other antimicrobial interventions such as methyl bromide, chlorine dioxide and sodium hypochlorite.

A fairly new antimicrobial intervention that is both effective and safe is ozone. The use of ozone is gaining popularity in drinking water, food processing and surface sanitation. While ozone is effective on a wide variety of pathogens, studies were done to prove that ozone is effective against the deadly strain of E.coli O157:H7. Research has been performed and ozone has proven to be a successful antimicrobial agent in the reduction of E.coli O157:H7. We have assembled a few research papers that used ozone on various food products to successfully reduce or eliminate E.coli O157:H7. These can be found  HERE.

Implementation of Ozone

Aqueous Ozone

The most common method of using ozone for pathogen reduction is dissolving ozone into water. Aqueous ozone is very stable, safe and easy to manage. Typically, ozone is dissolved into water using an ozone injection system and then sprayed onto the surface requiring disinfection. This surface may be a hard equipment surface or the surface of a food product.

Ozone levels of 2.0 ppm are commonly used for E.coli O157:H7 reduction. Only a few seconds of contact time of the aqueous ozone with the pathogen is necessary for inactivation.

Using this data, a determination of spray nozzles, spray bars or even conveyors 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 also 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.

Gaseous ozone

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.

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.

Efficacy of Gaseous Ozone Against Generic E.coli in Ground Beef

Resolution Concerning the Use of Ozone in Food Processing

Source: Dee Graham, "Ozone as an Antimicrobial Agent for the Treatment, Storage and Processing of Foods in Gas and Aqueous Phases," August 2, 2000.

The worldwide use of ozone as an effective sanitizer and disinfectant began in France in 1902 and has been documented in an expert panel report entitled "Evaluation of the History and Safety of Ozone in Processing Food for Human Consumption." This Declaration of GRAS Status for Use of Ozone in Food Processing was presented to the FDA on April 10, 1997 and published thereafter in the scientific literature and the trade press.

Numerous ozone applications have been installed throughout the food industry in the United States during the past two years. The benefits to public food safety are major, especially related to the food hazards identified in the President's Food Safety Initiative. These include newer pathogens such as E. coli 0157:H7, Listeria and resistant cyst formers such as Cryptosporidium and Giardia, all of which are inactivated effectively by ozonation.