Title: Effect of storage temperature on the survival and growth of Listeria monocyotogenes populations in the presence of indigenous surface microflora of fresh-cut cantaloupes Authors
Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: March 6, 2012
Publication Date: July 20, 2012
Citation: Ukuku, D.O., Olanya, O.M., Geveke, D.J., Sommers, C.H. 2012. Effect of storage temperature on the survival and growth of Listeria monocyotogenes populations in the presence of indigenous surface microflora of fresh-cut cantaloupes [abstract]. International Association for Food Protection Annual Meeting., July 20-25, 2012, Providence, Rhode Island. 1:1. Technical Abstract: The most recent outbreak of listerosis linked to consumption of fresh-cut cantaloupes contaminated by L. monocytogenes suggests the need to investigate the behavior of L. monocytogenes in the presence of native microflora of cantaloupe pieces during storage. The behavior of L. monocytogenes in the presence of native microflora of cantaloupe pieces during storage and the effect of waiting period before refrigeration on microbial populations on fresh-cut cantaloupes was investigated. Whole cantaloupes were inoculated with L. monocytogenes (8.35 log CFU/ml of suspension) for 10 min and air dried in a biosafety cabinet for 1 h and then were treated (unwashed, water washed and 2.5 % hydrogen peroxide (H2O2)). Fresh-cut pieces (~3 cm) prepared from these melons were left at 5 deg C and 10 deg C for 72 hours and room temperature (~20 deg C) for 48 hours. Some fresh-cut pieces were stored at 5 deg C after 2 hours and 4 hours of storage at 20 deg C. Microbial populations of fresh-cut pieces were determined immediately by the plate count or enrichment method after preparation and during storage. Aerobic mesophilic bacteria and yeast and mold of whole melon and inoculated populations of L. monocytogenes on cantaloupes rind surfaces averaged 6.5 log CFU/cm2, 3.3 log CFU/cm2 and 4.6 log CFU/cm2, respectively. Among the treatments, only H2O2 (2.5%) reduced the aerobic mesophilic bacteria, yeast and mold and L. monocytogenes populations to 2.8, 1.3 and 1.8 log CFU/cm2, respectively. The populations of L. monocytogenes transferred from melon rinds to fresh-cut were below detection (< 2 CFU/g). Storage temperatures enhanced the lag phases and growth of L. monocytogenes as evidenced by the increase in generation time, implying that these conditions could be a risk factor for produce contamination. Fresh-cut pieces with low populations of L. monocytogenes and approximately 2.8 log CFU/g mesophilic aerobic bacteria had an extended lag phase of 6 hours at 10 deg C and 4 hours at 20 deg C before growth of the pathogen could be detected. These results suggest that waiting period of 4 hours at 20 deg C before refrigeration of prepared fresh-cut cantaloupes enhanced growth of indigenous microflora and L. monocytogenes transferred to fresh-cut pieces suggesting the need for immediate refrigeration of prepared fresh-cut pieces at 5 deg C.