Ozonation in Food Applications

Ozone (O3) is a very unstable form of oxygen (O2). It is created naturally in the atmosphere, by the sun's ultraviolet rays on oxygen. Any energy source that is powerful enough to break the oxygen molecule will potentially generate ozone. Ozone is a powerful oxidizing agent. It is a more effective disinfectant than either chlorine or chlorine dioxide. It destroys bacteria,  yeasts, molds and parasites and is most effective when the pH level (amount of acidity or alkalinity) ranges between 6.0 and 8.5.

Ozonation  

Ozonation is the generation of ozone. It can be injected into water or air to destroy bacteria, etc. When it’s injected to treat water, it produces ozonated water.

Ozonation is most commonly used to treat municipal water supplies. Ozonation is also used in food and related industries:

  • for chemical-free sanitizing of food-contact surfaces, including conveyors
  • for bottled water production
  • for water-reconditioning or reuse
  • for sanitizing fresh fruit and vegetables for reducing pesticide levels on fresh produce
  • for sanitizing water to make ice 
  • for extending the shelf life of meat, fish, poultry and egg products
  • for sanitizing packaging and container material
  • for deodorizing air and water
  • for sterilizing  microbe-sensitive areas (ex: labs, food storage rooms)
  • for sterilizing and deodorizing food production and lab staff’s work clothes
  • as an alternative to chlorine

Generating ozone industrially

Ozone is created by using an electrical discharge (or corona discharge) between two electrodes in ambient air, oxygen gas, or oxygen-enriched air. Air can be enriched by removing nitrogen or adding oxygen. The ozone is then immediately injected into water to produce ozonated water or into a room to produce ozonated air (ex: labs or storage coolers).

A recent development in the food industry is ionizing the gases inside sealed food packages to create ozone that kills bacterial pathogens (ex: E.coli or Salmonella).

The capacity of ozone generators varies depending on the application. Large units treat more than 100,000 litres per hour in municipal water supplies. Small, countertop units treat 1,500 litres per hour in labs and food processing plants (ex: for cutting boards, utensils, hand sanitizing).  

Advantages of ozone for food processing

  • It only requires oxygen or air for its production.
  • It is faster and better at killing microbes than chlorine.
  • It is a non-thermal way to control pathogens and microbes in food processing.
  • It is a non-chemical alternative for treating water and sanitizing food contact surfaces.
  • It saves money because water does not have to be heated.
  • It is compatible with organic food processing.
  • It can be generated onsite, so no storage is required.
  • It leaves no residues in food or water.
  • It can be applied in an aqueous or gaseous state.

Disadvantages of ozone for food processing

  • It could damage rubber and other polymers used for gaskets and o-rings.
  • Its active life in water is less than 30 minutes, so it cannot be stored or moved.
  • Like chlorine  ozone is not selective. It will oxidize all organic material present. Depending on the soil load, its ability to kill micro-organisms may be restricted. So, when disinfecting water, the water should be pre-filtered before ozonation.

Health and safety

As with other powerful oxidizing agents, precautions are needed when using ozone. Good ventilation, extraction or inactivation systems are needed when using ozone because gas is given off during most ozonation processes. Ozone’s threshold limit value (TLV) is 0.1 parts per million (ppm). Anything above the threshold has potential health risks. When inhaled, ozone causes dry mouth, coughing and nose, throat and chest irritation. Ozone may also cause difficulty breathing, headaches or fatigue. The odour of ozone is easily smelled at concentrations as low as 0.01 to 0.05 ppm – which means workers are likely to smell it before it reaches a dangerous level.

Monitoring ozone levels in air can be done with commercially available test strips. A color change on the strips is matched to a standard scale. More sophisticated wall-mounted or hand-held devices are available and can measure such factors as ultra violet absorption that is specific to ozone.

Useful links

 

For more information, email the CVO/Food Safety Knowledge Centre or call 204-795-8418 in Winnipeg.