96-3 |
Effects of indigenous surface microflora of cantaloupe and washing treatment on survival and transfer of inoculated Listeria monocytogenes to fresh-cut pieces |
D. O. UKUKU and J. Davis. Plant Science & Technology Unit, USDA-ARS-Eastern Regional Research Center, 600 E. Mermaid Ln., Wyndmoor, PA 19038-8598 Cantaloupe melon has been associated with outbreaks of Salmonella and E. coli0157:H7. Because of the wide distribution of Listeria monocytogenesin the environment, potential presence of this organism on fresh-cut melons is of concern. Our objectives were to determine if indigenous surface microflora of cantaloupe affect L. monocytogenes attachment on cantaloupe surfaces and response to washing treatments. Melons treated with 70 % ethanol (EtOH) were inoculated by immersion in a L. monocytogenes (108 CFU/ml) suspension for 10 min, allowed to dry for 1 h, and then stored at 4oC or 20oC for up to 120 h. The inoculated melons were washed with 1000 mg/l chlorine or 5% hydrogen peroxide for 3 min following storage for 0, 24, 72 or 120 h. The indigenous microflora averaged 6.8 log10 CFU/cm2 and was reduced by 1.5 log following EtOH treatment. L. monocytogenes population on melon surface without EtOH pretreatment declined to 1.48 log10 CFU/cm2 and with EtOH pretreatment declined to 2.68 log10 CFU/cm2 during storage for 120 h at both temperatures. Indigenous surface microflora increased slightly during storage at 20oC. Chlorine and hydrogen peroxide treatments caused reduction of 3 log10 CFU/cm2 for the pathogen and 2.0 log10 CFU/cm2 for the indigenous microflora. Fresh-cut pieces prepared 24 h after inoculation without washing treatments were positive for L. monocytogenes while those prepared 72 h post inoculation were L. monocytogenes negative. Fresh-cut pieces from melons washed with chlorine or hydrogen peroxide solutions were negative for the pathogen. The inoculated pathogen survived but did not grow on fresh-cut tissues stored at 4 or 8oC for 6 days, These results suggest that the indigenous microflora of cantaloupe surfaces had little if any effect on survival of L. monocytogenes. Washing treatments have the potential to reduce L. monocytogenes population size and subsequent transfer from the rind to fresh-cut pieces.
Session 96, Fruit & Vegetable Products
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