Ozone can clean fruits and vegetables

USA Today (Society for the Advancement of Education), April, 2003

Ozone, the gas that protects the Earth from ultraviolet radiation, may soon give U.S. food shoppers better protection from harmful bacteria. Retailers could sanitize fruits and vegetables by exposing them to ozone before they go on sale, suggests Gary Rodrick, a professor with the University of Florida's Institute of Food and Agricultural Sciences, Gainesville. In Europe, ozone has been used for decades to sanitize water and food products.

"With a 99.9% kill rate, it's far more effective than current sanitizing methods, such as commercial fruit and vegetable washes," he argues. "The Food and Drug Administration recently gave the go-ahead to use it commercially in U.S. supermarkets and food-processing facilities. It also will be more acceptable than food irradiation, which has raised fears among some consumers."

Moreover, ozone used in food sanitation will not contribute to air pollution or smog. "In the upper atmosphere, ozone shields the Earth from ultraviolet radiation. In some urban areas, ozone forms at ground level when certain airborne chemicals interact with the sun's light and heat, contributing to smog. However, the sanitation process uses very low levels of ozone, and the entire process must be precisely controlled to be effective."

Ozone molecules contain three oxygen atoms and are formed when ordinary oxygen molecules containing two atoms are forced to take on a third. Rodrick says that ozone's usefulness as a sanitizing agent comes from its unstable molecular structure--the third oxygen atom tends to break apart from the ozone molecule, releasing energy. "When you expose an apple to ozone, bacteria on the fruit's surface will begin absorbing ozone molecules immediately. Those molecules break apart within seconds, and when they do the bacteria literally explode. The only waste product created is harmless oxygen, and it's unlikely that bacteria could overcome this technology by mutating into a resistant strain."

Rodrick has tested a commercial ozone sanitizing system developed by Fresh Food Technology in Burley, Idaho. Designed for use with fruits and vegetables, the system washes the items in ozone-enriched water. "We tested the system in supermarket produce departments. ... Ozone killed almost 100% of the bacteria on produce received from suppliers. In slightly higher concentrations, it also killed yeasts and molds."

He maintains that ozone sanitization increases the shelf life of fresh produce by up to two weeks. It also retards softening and browning. "Ozone works even better than we expected, and I think it will gain wide acceptance with U.S. consumers in the next few years. Post-harvest treatments of ready-to-eat produce are of paramount importance for preventing spoilage and minimizing the chance of food-borne infection. It's important that supermarkets do what they can to provide additional safeguards."

Currently, many supermarkets wash produce by soaking it in water mixed with a small amount of a commercial fruit and vegetable wash. The produce is then rinsed in pure water before being placed on sale. "That method has been adequate, but the effectiveness varies due to human error. You have to be mindful of the amount of wash used and the amount of produce involved. Ideally, you want a foolproof way to get uniform results."