Ozone in the food industry

Ozone is a gas that can be readily generated at point of use and used directly as an oxidising biocide, odour control agent or sterilising agent with food, beverages or site water. Its powerful oxidising action, fast reaction rate and acceptable reaction products have seen its use grow dramatically over the last decade. It dissolves readily in water where its sterilising properties are also used.

The relatively recent approval of ozone for use with food by the US Federal Drug Administration has resulted in the rapid expansion of ozone usage in food applications. This segment remains the fastest growing use of ozone gas. Typical food applications include:

• Washdown and use in pre-prepared food production facilities.
• Refrigerated storage of fresh produce from grower to supermarket - this controls fruit ripening, slows the spread or cross contamination from bacteria and rots, and ultimately extends the shelf life of the fresh produce.
• Sterilisation by ozone of meat, fish and poultry during processing. The odour controlling properties of ozone are also utilised in some of these markets.
• Ozonation of bread packaging to increase the shelf life and slow mould growth.
• Ozone use in greenhouse cultivation and purification of water for use in hydroponic growing.
• Water-bottling and beverage facilities.
• Sterilisation of food preparation utensils.

Ozone can be used for many reasons. In most applications it is a combination of performance, ease of implementation and cost-effectiveness:

• Performance: the cost of food product recalls from unacceptable microbiological levels, taints, moulds or rots is substantial.
• Ease of use: ozone can be readily controlled and lends itself well to automated systems. It can be generated at source and has no disposal issues.
• Cost effective: ozone can be generated inexpensively.

The American Environmental Protection Agency has laid down safe exposure levels for human contact with ozone. These levels are generally accepted in most parts of the world as being the standard for ozone exposure. The exposure levels are split into two parts:

1. Long term exposure level (LTEL) - human contact with ozone at levels of no more than 0.1 ppm in an eight-hour period is considered acceptable. An individual can be subjected to this level every day for a maximum of eight hours without experiencing any adverse effects.
2. Short term exposure level (STEL) - human contact with ozone at levels of no more than 0.2 ppm for a maximum period of 15 mins is considered acceptable. Again, an individual can be subjected to this level every day for 15 mins without experiencing any adverse effects.

There is a move to reduce the LTEL to 0.08 ppm in certain parts of the world but this has not yet become an established standard.

Ozone in air can be measured with three different technologies:

1. Gas sensitive semiconductor technology (GSS)
2. Electrochemical technology
3. Ultraviolet technology - this is the most costly system of measurement but also the most accurate and is usually restricted to scientific instruments.

GSS and electrochemical technologies are slightly less accurate, far more cost effective and are used in a huge array of applications.

The primary reason why ozone must be measured and controlled is for the health and safety of people coming into contact with the gas. Ozone in higher than recommended concentrations is known to cause and worsen respiratory disease. Ozone is also known to be an asthma trigger and high concentrations should be avoided by asthmatics and respiratory disease sufferers. This is why naturally occurring ozone in major cities needs to be monitored and if possible controlled.

The second reason ozone must be measured and controlled is for in-process-control in the many applications detailed above. The ozone levels must be high enough for the required sterilisation or deodorisation to be effective but also not too high so that it damages fresh produce or poses a threat to human health and safety.

Ozone if effectively controlled is a useful commodity with potential for deployment in increasing applications - the key is effective measurement and control.