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Sanitizing the Air

The rising acceptance and use of ozone in the produce industry

Food safety is top of mind in the produce industry, as everyone from growers to shippers to grocery stores look for ways to provide the healthiest fruits and vegetables to consumers.

While cleaning and sanitation has traditionally included chemicals to kill bacteria and contaminants, these come with their own safety and sustainability issues and provide no solution at all for organic growers. For a rising number of grower-shippers and suppliers, another solution has been gaining acceptance and producing results: ozone.

A Quick Trip back to Chemistry Class
Ozone has always been produced in nature, both by the sun’s ultraviolet rays and even by lightning. But, with a few simple ingredients, ozone can be manmade as well.

Although most people have probably heard of ozone, it is not in the most favorable light. While it is true ozone is a dangerous pollutant when found in the Earth’s lower atmosphere, there’s a flipside as well: ozone is also a valuable, beneficial part of the upper atmosphere.

So why should you care and what does it have to do with the fresh produce industry? The answer is simple: ozone can be a very effective oxidizing and sanitizing agent for perishables.

A Not-So-New Alternative
As far back as 2004, University of California, Davis professor Trevor Suslow (now director of the Postharvest Technology Center) wrote about its creation for use with postharvest fruits and vegetables. The article, “Ozone Applications for Postharvest Disinfection of Edible Horticultural Crops,” explained how specialized equipment could pass normal or oxygen-enriched air across an ultra violet light source, or use high electric voltage to create ozone.

Beth Hamil is the vice president of corporate operations and a food safety consultant at DEL Ozone, in San Luis Obispo, CA. She explained that this process gives an extra charge to some of the air’s regular oxygen molecules (O₂), causing them to split. These single (O) molecules bond with normal oxygen molecules (O₂ + O) to create ozone (O₃)—for further information, see the sidebar and diagram on this page.

For oxygen, three’s a crowd, and that extra atom makes the ozone molecule unstable and highly reactive. This is a good thing for two reasons: first, when bacteria is exposed to ozone molecules, the extra atom jumps ship and attaches to the bacteria cells, causing them to burst and die.

Second, because ozone is so unstable, it breaks down quickly and easily, turning back into harmless oxygen.

In addition, Hamil relates that ozone has a very short half-life of seconds to hours, depending on the type and other factors.

Although ozone has been used for many years to disinfect municipal water, bottled water, and even swimming pools, it has only been used in direct contact with food for about two decades, after gaining federal approval.