Wet vs. dry inoculation methods have a significant effect of Listeria monocytogenes growth on many types of whole intact fresh produce

What is it about?

L. monocytogenes causes relatively few outbreaks linked to whole fresh produce but does trigger recalls each year. There are limited data on the influence of wet vs. dry methods on pathogen growth on whole produce. We studied blackberry, raspberry, blueberry, lemon, mandarin orange, sweet cherry, tomato, cauliflower broccoli and carrot. Intact, whole inoculated commodities were stored at 2, 12, 22 and 35 °C. Use of a liquid inoculum (vs. dry inoculum) resulted in markedly increased L. monocytogenes growth rate and magnitude on whole produce surfaces. This difference was highly influenced by temperature with a greater effect seen with more commodities at higher temperatures (22 and 35°C), versus lower temperatures (2 and 12 °C). These findings need to be explored for other commodities and pathogens. The degree to which wet or dry inoculation techniques more realistically mimic contamination conditions throughout the supply chain should be investigated.

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