Irradiation of Vegetables and Fruits

Those in favour of natural, organic produce are predictably against it. Health authorities often advocate it. Any word that implies radiation is likely to promote anxiety. But is this fear well founded or is it just another come-on by extremist environmental groups intent on keeping the pot boiling?

A decade ago, Australia and New Zealand’s joint regulator of food standards reject some one thousand submissions against the irradiation of fruits and vegetables, declaring the process to be safe. However, in those nations where food costs are high by North American standards and concerns perhaps more pronounced, little has altered since that time. Only irradiated mangoes, papaya and lychees have been approved for sale. Now this has changed as irradiated tomatoes and peppers flood New Zealand retail outlets. Imported from Australia to meet the seasonal shortages of winter in the antipodal nation, they were first irradiated to prevent much-feared fruit flies accompanying them. New Zealand exports much produce to eastern Asian countries and even the hint of a feared fruit fly could result in loss of much appreciated income. But one blast of gamma rays and bye-bye fruit fly.

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Irradiation also eliminates the health risks of produce contaminated by bacteria and other disease-causing organisms. Some researchers have maintained that the devastating consequences of contaminated organic bean sprouts distributed in Europe a few years ago might have been entirely eliminated had they first been irradiated. Over twenty years ago, the United States Department of Agriculture approved of the technique for first poultry and then other meats, all notorious potential sources of botulism. So why hasn’t gamma irradiation seen far wider use on other food products? In the March 2006 Journal of Food Production, a team from Texas A&M University described the results of exposing fresh-cut tomatoes to salmonella to irradiation. The experiment was highly successful in reduction of the bacteria. However, the researchers reported that while they had not conducted follow up taste tests on the tomatoes, irradiation damages the texture of grapes, among other fruits and vegetables. It also may reduce their nutritional value by affecting vitamins they contain. Professor Jorge M. Fonseca at Arizona State University has confirmed this. He was quoted in the November-December 2007 American Scientist as saying that the “dose needed to get rid of pathogens can have an unwelcome effect on pectic substances in the cell walls of the plant, causing the tissue to soften.” There are also extensive mechanical requirements, he noted. Indeed, the cost of the equipment would eliminate its use by any but the largest distribution centres, as appears to be the case in the tomatoes and peppers exported from Australia to New Zealand. So while it might reduce vegetable and fruit bacterial loads, the reduction in texture, flavour and perhaps nutritional value appear to rule against gamma irradiation being commonly used in this field anytime soon. Good news certainly for many concerned consumers as well as billions of bacterium faced with the prospect of being fried by a blast of gamma rays.