WESLACO Scientists at Texas A&M and the U.S. Department of Agriculture in South Texas are studying the irradiation of grapefruit to extend its shelf life, provide a safe and effective quarantine treatment against fruit flies and increase levels of vitamins and other healthful compounds.
Dr. Bhimu Patil, a post-harvest physiologist at the Texas A&M-Kingsville Citrus Center at Weslaco, and Dr. Guy Hallman, a research entomologist at the Kika de la Garza USDA-ARS Subtropical Ag Research Center in Weslaco, have been treating grapefruit with various low doses of gamma rays at the Mexican fruit fly rearing facilities of the USDA-APHIS Plant Protection and Quarantine at Moore Airbase in Mission.
“With EPA phasing out the use of methyl bromide fumigants to treat for fruit flies, we need to find alternative methods,” Patil said. “We know irradiation works as a quarantine treatment. What we don’t know is how irradiation affects fruit quality and shelf life.”
To find out, Patil and Hallman have treated some 80 grapefruit at five different doses, all below the maximum dose recommendations of the Food and Drug Administration. Treatments will be repeated over a two-year period.
“We should have some preliminary results this summer,” said Patil, “but based on irradiation studies done on onions, I suspect we’ll see an increase in the levels of phytonutrients, those naturally occurring chemical compounds in fruits and vegetables that have been shown to prevent certain cancers in humans.”
In studies he did to earn his doctorate degree at Texas A&M University in College Station, Patil said irradiating onions increased levels of antioxidants known as flavonols (quercetin). He suspects similar treatments on grapefruit will increase levels of naringin, an antioxidant shown to be one of the components that may prevent breast cancer.
Patil said other studies in Florida have shown that irradiating oranges at low doses increases levels of sugars. But tests were not performed on the resulting fruit color, taste, levels of phytonutrients, or what effects higher doses would have.
“Irradiation is used all over the world to treat meat, fruits and vegetables to kill pathogens without using potentially harmful chemicals,” Patil said. “So what we’re doing are pro-active studies. If we’re going to use irradiation here, we need to know now how these treatments affect fruit quality so as not to delay implementation.”
Patil said he envisions large border irradiation facilities that will treat imported food products as well as domestic foods such as citrus that are sometimes quarantined from interstate shipping to prevent the spread of pests and pathogens.
“If we can increase the shelf life and the healthful benefits of fruits and vegetables in the process, so much the better,” Patil said.
Hallman said that irradiation has a successful track record of almost five years in ridding Hawaiian fruit of Mediterranean fruit flies and Florida guavas of Caribbean fruit flies. Mangos that will be harvested in Florida in May will also be irradiated. Hallman has completed research showing that low-dose irradiation can be used to disinfest Texas citrus of Mexican fruit fly.
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