19-1 |
Enhancement of safety and shelf-life of fruits and vegetables by irradiation |
D. M. FOLEY, Div. of Natural & Applied Sciences, Chapman Univ., 1 University Dr., Orange, CA 92866 Non-thermal processing techniques such as irradiation have the potential to improve safety without reducing the fresh-like qualities of minimally processed vegetables. Optimization, using combination processing, can also result in enhanced shelf-life. In this presentation, effects of irradiation processing on microbial and sensory attributes of various fresh-cut products will be demonstrated. Using a protocol designed to recover injured cells, survival of E. coli 0157:H7 was evaluated in shredded iceberg lettuce and cilantro inoculated with a six-strain cocktail E. coli 0157:H7, chlorinated at 200 mg/mL, and irradiated at 0.5 kGy using a Cobalt60 source. Chlorination plus irradiation produced more than a 4.5 log reduction in E. coli 0157:H7 levels for both cilantro and lettuce. Irradiation at this level did not cause softening or wilting and sensory attributes were not adversely affected for either product. Diced Roma tomatoes and diced bell peppers were irradiated at several low levels and evaluated for changes in microbial, physical, chemical and sensory properties. The total plate counts and yeast and molds were significantly reduced in the irradiated samples. At dose levels greater than 1 kGy, loss of firmness was a limiting factor in acceptability of the product, however, at low-dose levels, the change was not detectable by a 9-member trained sensory panel. A six-log reduction in L. monocytogenes inoculated into refrigerated avocado pulp was observed following irradiation at 3 kGy, although no significant reduction was observed at 1 kGy . Adjusting the pH to as low as 4.5 did not inhibit Listeria survival in avocado pulp and did not enhance irradiation sensitivity. Although activity of polyphenoloxidase was slightly enhanced, there was no perceptible change in rate of browning. Other sensory attributes, such as flavor and odor were not affected by irradiation.
Session 19, Emerging technologies for enhancement of fruit and vegetable quality and safety
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