Location: Environmental Microbial & Food Safety Laboratory
Project Number: 8042-32420-009-012-S
Project Type: Non-Assistance Cooperative Agreement
Start Date: Jan 1, 2019
End Date: Jul 31, 2021
Objective:
To 1). Determine Listeria monocytogenes (Lm) growth potential and kinetics on major classes of whole and fresh-cut produce under normal storage/retail display conditions; 2). Determine Lm growth potential and kinetics under temperature abuse conditions and develop an indexing system for quantifying temperature abuse; 3). Determine produce nutritional and physiochemical characteristics on Lm growth potential and kinetics; and 4). Evaluate the effects of the indigenous microbial community from produce on Lm growth.
Approach:
A large selection of whole and fresh-cut produce representing major fresh commodity categories, including but not limited to, leafy greens, melons, fleshy vegetables, root vegetables, berries, and tree fruits will be evaluated for supporting Lm growth at typical commercial storage and retail display conditions for up to twice the typical shelf life. Selected products will be inoculated with Lm strains and stored at conditions simulating the pre-market storage and retail display conditions for the time length that can reflect Lm growth potentials and kinetics during the storage/display processes. The inoculated products will be periodically sampled over the storage time to determine Lm growth kinetics on individual products. A smaller set of fresh-cut products will be selected for assessing Lm growth potential and kinetics under temperature abuse storage conditions. Multiple constant elevated temperatures will be tested to generate empirical growth models for Lm on specific products, which will be used to calculate an index for Time Factored Temperature Abuse (TFTA). The predicted Lm growth will be compared to experimental observations using Lm inoculated products that are exposed to randomized temperature abuse conditions. The effects of produce intrinsic characteristics on Lm growth, including nutrient availability and physiochemical properties (pH and anti-listerial substance etc) will be correlated to the growth potentials. The microbiome on selected whole and fresh-cut products will be profiled using bacterial 16S rRNA gene sequencing surveys and bacterial community analyses.
