30B-15 |
Effect of gamma irradiation on microbiological and sensory quality of shredded iceberg lettuce |
L. RODRIGUEZ1, A. Dufour2, D. Foley3, F. Caporaso2, and A. Prakash2. (1) Food Science and Nutrition, Chapman University, One University Drive, Orange, CA 92866, (2) Department of Food Science and Nutrition, Chapman University, One University Dr., Orange, CA 92866, (3) Department of Biological Sciences, Chapman University, One University Dr., Orange, CA 92866 Bagged shredded iceberg lettuce is a popular retail and food service product but the lack of lethal treatment allows the potential of pathogens such as Escherichia coli 0157:H7 being present. Non-thermal processing techniques such as irradiation have the potential to improve safety without reducing the fresh-like qualities of fresh-cut lettuce. The objective of this study was to determine the effectiveness of chlorination and low-dose irradiation in eliminating E. coli 0157:H7 from inoculated shredded iceberg lettuce and to determine the changes in physical and sensory attributes as a result of such processing. Lettuce was inoculated with a six-strain cocktail of acid adapted E. coli 0157:H7 at a level of 1 x 107 CFU/gram. Following chlorination at 200 mg/mL, the lettuce was irradiated at 0.15 kGy, 0.35 kGy, or 0.59 kGy using a Cobalt60 source. Survival of E. coli 0157:H7, aerobic mesophiles and yeast and molds were measured over a period of 10 days. Changes in texture and color were determined by instrumental means and changes in flavor, odor, and visual quality were determined by sensory testing. Chlorination plus irradiation at 0.59 kGy produced a 5.4-log reduction in E. coli 0157:H7 levels whereas chlorination alone reduced the E. coli 0157:H7 counts by 1-2 logs. E. coli counts decreased further in 0.59 kGy irradiated lettuce with storage and were undetectable by Day 7. Irradiation at 0.59 kGy was also effective in reducing standard plate counts by 4 logs and yeast and mold counts by 3-4 logs; these differences were maintained throughout the storage period. Irradiation at this level did not cause softening of lettuce and sensory attributes were not adversely affected. The 5+ log reduction in E.coli counts and lack of adverse effects on sensory attributes indicate that low-dose irradiation can improve the safety and shelf-life of fresh-cut iceberg lettuce for retail sale or food service.
Session 30B, Fruit & Vegetable Products: Sensory, Product Development, Fresh-Cut, and Storage
|