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A. PRAKASH, Department of Food Science and Nutrition, Chapman University, One University Drive, Orange, CA 92866

Fresh and minimally processed fruits and vegetables are often considered to be among the most healthful and safe foodstuffs available, yet several outbreaks of foodborne illness have been linked to their consumption. In addition, numerous isolations of pathogenic organisms from fresh fruits and vegetables have been documented. Contamination of minimally processed vegetables is of concern because these products are usually consumed in the fresh state without further protective treatment.

The efficacy of irradiation stems from the fact that its biocidal effectiveness is not limited to the surface, since it can penetrate the product and eliminate microorganisms that are present in crevices and creases (significant for vegetables like lettuce and cabbage), pockets, and natural openings in the skin, as well as the interior.

A long-held belief is that vegetable tissues are susceptible to damage by irradiation, even at low levels. Another belief is that irradiation levels that do not cause tissue damage have a minimal effect on microorganisms. Some vegetables, especially leafy vegetables, are sensitive to damage by irradiation; however, not enough work has been done at low dose levels (less than 1 kGy) and on pre-cut products.

Recent work on shredded carrots, pre-cut bell peppers, shredded iceberg lettuce, cut romaine lettuce, diced celery, and other ready-to-eat vegetables has shown that microbial and pathogen counts can be significantly reduced by low-dose irradiation without affecting sensory characteristics. Furthermore, by combining irradiation with other bactericidal and bacteriostatic treatments such as chemical sanitation, modified-atmosphere packaging, and refrigeration, a greater overall effect on the microbial load of a product may be realized than when compared to a single extreme treatment that could be detrimental to sensitive plant tissue.