P2-98 Growth of Listeria monocytogenes on Fresh-cut Pieces of Cantaloupe from Two Different Varieties during Storage

Tuesday, August 2, 2016
America's Center - St. Louis
Esmond Nyarko, University of Delaware, Newark, DE
Kali Kniel, University of Delaware, Newark, DE
Russell Reynnells, University of Maryland Eastern Shore, Princess Anne, MD
Cheryl Roberts, U.S. Department of Agriculture-ARS-EMFSL, Beltsville, MD
Eric Handy, U.S. Department of Agriculture ARS EMFSL, Beltsville, MD
Yaguang Luo, U.S. Department of Agriculture-ARS, Beltsville, MD
Patricia Millner, U.S. Department of Agriculture ARS EMFSL, Beltsville, MD
Manan Sharma, U.S. Department of Agriculture, Beltsville, MD
Introduction: ‘Rocky Ford’ cantaloupes were implicated in the U.S. multi-state outbreak of listeriosis in 2011. Listeria monocytogenes can survive on whole cantaloupes during storage, and may be transferred to flesh of melons.

Purpose: The growth of L. monocytogenes on fresh-cut ‘Athena’ and ‘Rocky Ford’ cantaloupe cultivars during refrigerated storage was evaluated. 

Methods: Fresh-cut cubes (1 in3) of cantaloupes inoculated with a multi-strain inoculum of L. monocytogenes (5 log CFU/cube) were stored at 4°C and 10°C for up to 7 days. Also, inoculated fresh-cut cubes were continuously stored at 4°C for 3 days or stored at 4°C and subjected to temperature abuse (TA – 25°C/4 h) events on days 0 and 1, and then stored at 4°C until day 3. L. monocytogenes populations were determined on selected days and after each TA event.  Brix values were measured for both cantaloupe cultivars. An ANOVA was performed to determine storage temperature and cultivar effects on L. monocytogenes populations on fresh-cut cubes. 

Results: L. monocytogenes populations on fresh-cut cantaloupes stored at 4°C increased by approximately 1 log CFU/cube by day 7, whereas populations increased by approximately 3.5 log CFU/cube on those stored at 10°C by day 7. L. monocytogenes populations on fresh-cut cantaloupes stored at 10°C were significantly (P<0.05) greater than those stored at 4°C. Growth of L. monocytogenes on ‘Athena’ and ‘Rocky Ford’ fresh-cut cantaloupes were similar, although ‘Athena’ had significantly (P<0.05) greater Brix values than ‘Rocky Ford’ cantaloupes.  L. monocytogenes populations on fresh-cut cantaloupes subjected to TA were approximately 0.74 log CFU greater than those that were continuously stored at 4°C at day 3.

Significance: L. monocytogenes populations grew on fresh-cut cantaloupes stored at both 4°C and 10°C, and temperature abuse events promoted growth of L. monocytogenes on fresh-cut cantaloupe cubes, even when stored at 4°C.