When we think of ozone, it is usually in the context of “the ozone layer,” earth's protection from solar radiation. But Jim Hatton, of Semco Manufacturing in Pharr, Texas, contends that ozone will soon replace chlorine as the disinfectant of choice, not only for water supplies and swimming pools but also for disinfecting fruits and vegetables before storage or packing and shipping.

“Ozone has been used extensively in the fruit and vegetable industry in Europe, but only recently has it started proving its effectiveness in processing and packing plants in the United States,” said Hatton, a speaker at the Texas Vegetable Association Meeting in McAllen, Texas.

Occurs naturally

The power of ozone, a naturally occurring gas, lies in its ability to decompose, quickly bursting the cell wall of a bacterium, allowing the contents to spill out and then be immediately oxidized and destroyed.

Ozone treatment kills all known organisms and viruses. This rapid and complete oxidation of contaminants insures that the bacteria or virus will not develop an immunity or resistance to the gas.

The preferred method for treatment consists of submersion of vegetables into tanks of treated water that agitates around the product. Water and suspended organic solids are then continually recirculated through a filtration system to guard against cross-contamination and to keep the oxidation-reduction potential of the water at a desired range.

Ozone far surpasses chlorine, the most common disinfectant used for sanitizing fruits and vegetables, in many aspects. It has been estimated that up to 30 percent of all fresh produce is lost during the period between harvest and consumption due to microbial spoilage. One of the most important benefits for vegetables treated with ozone, in the form of ozonated water, compared to those treated with chlorinated water, is the extension of market quality storage life, in some cases more than doubling it. Ozone treated produce also has a better flavor.

Ozone has an oxidation potential that is over one-and-a-half times more powerful than chlorine. Because the contact time required to kill the microorganisms is much shorter with ozone, it is often 50 to 100 times more effective as a disinfectant than chlorine. Ozone uses less water than chlorine and does not react with organic materials to form by-products that have been implicated as carcinogens like chlorine does and, since it is chemical free, breaks down into simpler compounds, so the water it sheds contains no toxic residues and can be recycled. Unlike chlorine, it is generally non-corrosive to metal equipment at the concentration used for disinfecting.

More effective

In 1991 the Environmental Protection Agency confirmed that ozone is far more effective than conventional disinfectants against microbial contaminants, including E-coli, Salmonella, Giardia and Cryptosporidium. Ozone can be up to 300 times more effective against Giardia, for instance, than disinfection with chlorine.

Newspaper reports of illnesses directly linked to contaminated foods make consumers concerned over the safety of their produce. With ozone treated produce, consumers can be assured that their fruits and vegetables are “good enough to eat.”

GRAS (Generally Recognized As Safe) status on fresh vegetables is currently under consideration by the FDA and is expected soon. “After the GRAS status is approved, I expect to see more processors and packers experimenting with ozone,” Hatton say. “And as more successful systems start showing up, the industry will put pressure on other shippers to change over. How quick this takes place will depend on the cost of the equipment and how many more outbreaks occur from foodborne pathogens.”