Research – ComBase models are valid for predicting fate of Listeria monocytogenes on ten whole intact raw fruits and vegetables

Journal of Food Protection

L. monocytogenes was associated with more than 60 produce recalls between 2017 and 2020 including tomato, cherry, broccoli, lemon, and lime recalls. This study describes the effects of temperature, time and food substrate as factors influencing L. monocytogenes behavior on whole intact raw fruits and vegetables. A cocktail of five L. monocytogenes strains previously associated with foodborne outbreaks were used. Ten intact whole fruit and vegetable commodities were chosen based on data gaps identified in a systematic literature review. Produce investigated belong to major commodity families: Ericaceae (blackberry, raspberry, and blueberry), Rutaceae (lemon and mandarin orange), Roseaceae (sweet cherry), Solanaceae (tomato), Brassaceae (cauliflower and broccoli) and Apiaceae (carrot). Intact inoculated whole fruit and vegetable commodities were incubated at 2, 12, 22, 30 and 35 °C with relative humidities matched to typical real-world conditions. Foods were sampled (n=6) for up to 28 days, depending on temperature. Growth and decline rates were estimated using the DMFit for Excel. Growth rates were compared with ComBase modeling predictions for L. monocytogenes. Almost every experiment showed initial growth, followed by subsequent decline. L. monocytogenes was able to grow on whole intact surface of all produce tested, except for carrot. The 10 produce commodities supported growth of L. monocytogenes at 22 and 35°C. Growth and survival at 2 and 12°C varied by produce commodity. The standard deviation of the square root growth and decline rates showed significantly larger variability in both growth and decline rates within replicates as temperature increased. When L. monocytogenes growth occurred, it was conservatively modeled by ComBase Predictor, and growth was generally followed by decreases in concentration. This research will assist in understanding the risks of foodborne disease outbreaks and recalls associated with L. monocytogenes on fresh whole produce.

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