Listeria monocytogenes growth and survival on peaches and nectarines as influenced by stone fruit packing house operations, storage and transportation conditions.

Listeria monocytogenes growth and survival on peaches and nectarines as influenced by stone fruit packing house operations, storage and transportation conditions.

Jan. 1, 2017 - Dec. 31, 2017

2017-123F

$94,410.38

Mary Anne Amalaradjou, Ph.D.
University of Connecticut

Final Report

Publication

The recent multi-state Listeria monocytogenes outbreak associated with stone fruit consumption highlights the potential for stone fruits to serve as a vehicle in Listeria transmission. Further, the outbreak also demonstrates the pathogen’s ability to persist and survive on stone fruits during handling, storage and transportation. While investigations on the persistence of Listeria have been performed on other produce, there is a general lack of knowledge on the behavior of pathogens associated with stone fruits.  Additionally, each produce type has unique compositional and physical characteristics that require produce-specific management practices. Therefore, to develop stone fruit-specific risk reduction knowledge and preventive controls, this study will investigate the survival and growth of Listeria on peaches and nectarines under packing house environment, storage and transportation conditions. The study will be performed under conditions simulating stone fruit unloading and staging, waxing and fungicide application, storage and transportation from the packing facility.  It is expected that results from this study will provide quantifiable data on the effect of current practices on Listeria survival on stone fruits. Furthermore, identification of food safety risks associated with different steps within the packing house continuum will help develop comprehensive preventive controls for foodborne pathogens including Listeria monocytogenes.

Technical Abstract

The recent recall of stone fruits due to potential Listeria monocytogenes contamination and the stone fruit associated multi-state outbreak establishes a novel link between human listeriosis and stone fruit consumption. The outbreak further highlights the pathogen’s ability to survive and persist on stone fruits through the handling, storage and transportation chain. This is of particular concern with fresh fruits like peaches and nectarines since there is no kill step that will effectively eliminate the pathogen prior to ingestion.  Therefore, there is a critical need for quality control in stone fruits intended for human consumption. In order to develop effective food safety practices, it is essential to understand the influence of fruit processing, storage and transportation conditions on pathogen survival and growth. Although several studies have demonstrated the effect of processing and storage conditions on Listeria monocytogenes survival on produce, there is a general lack of knowledge on the behavior of pathogens associated with stone fruits. Moreover, each produce type has unique compositional and physical characteristics that require specific growth conditions, harvesting protocols, processing practices and storage conditions. Hence food safety practices and preventive controls must be highly produce-specific. Therefore, to develop risk reduction practices to eliminate potential foodborne hazards from stone fruits, this study will investigate the influence of stone fruit packing house, storage and transportation conditions on Listeria survival and growth on peaches and nectarines. In order to simulate commercial practices, Listeria survival will be evaluated under stone fruit unloading and staging, waxing and fungicide application and cooling, storage and transportation conditions. It is expected that results from this study will provide quantifiable data on the ability of Listeria to persist (survival/growth) on stone fruits under current processing conditions. Identification of food safety risks associated with a process or multiple processes within the packing house continuum will help develop comprehensive preventive controls for foodborne pathogens including Listeria monocytogenes.

Research Objectives   

            The overall objective of this proposal is to investigate the survival and growth of Listeria monocytogenes at high (5 log CFU/fruit) and low inoculation (3 log CFU/fruit) levels on yellow flesh peach (var. Autumn Flame) and nectarine varieties (var. August fire) as influenced by stone fruit post-harvest processing, cooling, storage and transportation conditions. In order to simulate post-harvest handling of stone fruits, Listeria survival will be evaluated at three different steps in the process, which include:

Objective 1: Effect of unloading and staging conditions at the stone fruit packing facility [temperature - 18-20 or 28-30°C (ambient cool and warm season temperature), RH – 40-50% (ambient humidity), length of storage (1 to 18 h)] on Listeria monocytogenes growth and survival on peach and nectarine varieties.

Objective 2: Effect of fruit waxing (mineral-oil and vegetable-oil based fruit finish) and fungicide application (Fludioxonil and Propiconazole) at the stone fruit packing facility [(temperature- 18-20 or 28-30°C (ambient cool and warm season temperature), RH – 40-50% (ambient humidity), length of storage (1 to 6 h)] on Listeria monocytogenes growth and survival on peach and nectarine varieties.

Objective 3: Effect of cooling, storage and transportation [temperature - 1-2°C, RH 85-95%, length of storage - 4 weeks] conditions at the packing facility on Listeria monocytogenes growth and survival on peach and nectarine varieties.

The temperature, relative humidity and time factors to be used in the study were determined based on the Food safety guidelines for fresh, whole stone fruit produced in California’s San Joaquin valley (CCFA, 2015) and discussions with the California Fresh Fruit Association.