P1-46 The Effect of Postharvest Practices on Listeria monocytogenes Contamination and Survival in Apple Fruit

Monday, August 1, 2016
America's Center - St. Louis
Ishani Sheth, U.S. Food and Drug Administration-CFSAN, College Park, MD
Minji Hur, Gachon University, Seoul, Korea, The Republic of
Anna Wooten, U.S. Food and Drug Administration-CFSAN, College Park, MD
Antonio J. De Jesús, U.S. Food and Drug Administration-CFSAN, College Park, MD
Seonjae Bae, Gachon University, Seoul, Korea, The Republic of
Wayne Jurick, U.S. Department of Agriculture-ARS, Food Quality Laboratory, Beltsville, MD
Yi Chen, U.S. Food and Drug Administration-CFSAN, College Park, MD
Dumitru Macarisin, U.S. Food and Drug Administration-CFSAN, College Park, MD
Introduction: Apples emerged as a new concern for Listeria monocytogenes contamination in the past few years. The 2012 Missa Bay LLC, 2015 Northstar Produce Inc. and Del Monte Fresh Produce N.A. Inc. multistate recalls of whole fresh apples due to contamination with L. monocytogenes clearly indicates the need for investigating the origin, spread, and persistence of this pathogen on pome fruits.

Purpose: Evaluate the effect of current postharvest practices used at commercial fruit packing facilities on the contamination and persistence of L. monocytogenes in intact apples.

 Methods: Freshly harvested Granny Smith apples and two L. monocytogenes outbreak strains linked to caramel apples were evaluated. To imitate apple contamination during dump-tank washing, fruits were immersed into contaminated water (6 log CFU/ml) to various depths (surface, 1 and 2 feet) for 20 min. To track water uptake by apples, Acid Blue 9 dye (100 mg/ml) was dissolved in the water. Seven days after inoculation, detection and enumeration of L. monocytogenes internalized into different areas of the apple fruit core was conducted following FDA-BAM protocols.

Results: Dye infiltration into apple core was observed from both calix and stem ends of the fruit. Under experimental conditions L. monocytogenes internalized into inner calix and stem areas of the apple core during the dump tank washing.  One week after inoculation bacterial populations in inner core ranged from 1 to 3 log CFU/g.  The incidence of L. monocytogenes infiltration significantly (P≤0.5) varied among treatments and was 52.1, 65.0 and 81.6% for the surface, 1 and 2 feet for immersed apples, respectively. No difference in L. monocytogenes infiltration incidence was observed between calix and stem inner sinuses of Granny Smith apples.

Significance: Identification of postharvest practices potentially facilitating contamination and survival of L. monocytogenes in apples will permit prevention of future recalls and outbreaks of foodborne listeriosis associated with consumption of pome fruits.