By Sharon Omahen
University of Georgia
Due to the recent E. coli O157:H7 outbreak, spinach and other bagged produce are on the minds of most Americans. But University of Georgia food microbiologist Larry Beuchat says fruits such as blueberries, strawberries and raspberries are safety concerns, too.
For the past 10 years, Beuchat has evaluated the effectiveness of new methods of sanitizing fresh fruits and vegetables.
"There are a number of sanitizers used in the industry," he said. "There are also a number of new ones that need to be evaluated for efficacy. We need to know if they can really do the job."
Chlorine is the standard
A University System of Georgia distinguished research professor with the UGA Center for Food Safety, Beuchat says chlorine, the standard sanitizer used in the food industry, isn't ideal for use on many small fruits.
"You can't sanitize these fresh-market fruits with chlorine because they're too tender and can't withstand the process," he said. "And if all the water isn't removed, the chances for mold growth are greatly enhanced."
One method Beuchat has evaluated uses chlorine dioxide gas to kill microorganisms like Salmonella, E. coli 0157:H7 and Listeria monocytogenes. He tested this sanitizer on both whole produce and fresh-cut, bagged produce.
Samples of cabbage, carrots, lettuce, whole apples, peaches, onions and tomatoes were inoculated with pathogens and then treated with chlorine dioxide.
Safe, but not appealing
"The gas treatment not only killed most of the pathogens and spoilage microorganisms, including molds and yeasts, it avoided the problems associated with washing small fruits," he said. Unfortunately, it also produced some negative effects.
"The gas changed the visual appearance of some of the fruits' surfaces which consumers may not find acceptable," he said. "Cut carrots were slightly bleached. It had a browning effect on peaches and lettuce."
Beuchat says the gas treatment "shows promise." But he doesn't think the industry will quickly accept and apply it, due in part to the cost of installing the necessary equipment.
"Continued work is also needed to define the concentration, time of exposure and temperature at which fruits and vegetables should be exposed," he said.
Funded by the Food Processing Council of Georgia (FoodPAC), Beuchat's research has been published in the Journal of Food Protection and the Georgia Fruit and Vegetable Growers News.
Don't wash bagged produce
In the meantime, Beuchat offers some safety tips for people at home.
"If you buy fresh-cut, bagged lettuce, cabbage or spinach, don't wash the produce at home," he said. The produce was treated with sanitizers before it was packaged.
"In my opinion, there's a much higher chance of contaminating the produce by washing it at home than there is of it being contaminated in the bag," he said.
When preparing fresh berries, like strawberries, blueberries and raspberries, throughly wash them at home. Wash these small fruits with tap water just before you serve them to your family, Beuchat said.
"Don't wash them until you are ready to serve them," he said. "If you wash them and then put them in your refrigerator, you can create a moist environment for mold to develop."
(Sharon Omahen is a news editor with the University of Georgia College of Agricultural and Environmental Sciences.)