Growth Kinetics of Listeria monocytogenes in Cut Produce

Abstract

Cut produce continues to constitute a significant portion of the fresh fruit and vegetables sold directly to consumers. As such, the safety of these items during storage, handling, and display remains a concern. Cut tomatoes, cut leafy greens, and cut melons, which have been studied in relation to their ability to support pathogen growth, have been specifically identified as needing temperature control for safety. Data are needed on the growth behavior of foodborne pathogens in other types of cut produce items that are commonly offered for retail purchase and are potentially held without temperature control. This study assessed the survival and growth of Listeria monocytogenes in cut produce items that are commonly offered for retail purchase, specifically broccoli, green and red bell peppers, yellow onions, canned green and black olives, fresh green olives, cantaloupe flesh and rind, avocado pulp, cucumbers, and button mushrooms. The survival of L. monocytogenes strains representing serotypes 1/2a, 1/2b, and 4b was determined on the cut produce items for each strain individually at 5, 10, and 25°C for up to 720 h. The modified Baranyi model was used to determine the growth kinetics (the maximum growth rates and maximum population increases) in the L. monocytogenes populations. The products that supported the most rapid growth of L. monocytogenes, considering the fastest growth and resulting population levels, were cantaloupe flesh and avocado pulp. When stored at 25°C, the maximum growth rates for these products were 0.093 to 0.138 log CFU/g/h and 0.130 to 0.193 log CFU/g/h, respectively, depending on the strain. Green olives and broccoli did not support growth at any temperature. These results can be used to inform discussions surrounding whether specific time and temperature storage conditions should be recommended for additional cut produce items.

Sources and survival ofListeria monocytogeneson fresh, leafy produce

“…), green and red peppers and avocado pulp (Salazar et al . ). Studies such as these have outlined the importance of keeping produce at refrigeration temperatures to slow growth of L. monocytogenes populations, but have also demonstrated that postharvest, L. monocytogenes can survive on the surface of fresh produce for extended periods.…”

“…Conversely, L. monocytogenes can proliferate when in contact with a substrate such as cut produce (Salazar et al . ), but more research is needed to determine its growth behaviours specifically for fresh leafy produce. Additionally, more investigation is required to determine the effect that this change in environments has on the culturability and infectiveness of this pathogen.…”

“…When contamination does occur, the amount of L. monocytogenes transferred to product is likely to be small/minimal based on previous data on the number of L. monocytogenes present in soil (Locatelli et al 2013a). Conversely, L. monocytogenes can proliferate when in contact with a substrate such as cut produce (Salazar et al 2017), but more research is needed to determine its growth behaviours specifically for fresh leafy produce. Additionally, more investigation is required to determine the effect that this change in environments has on the culturability and infectiveness of this pathogen.…”

“…It has been shown that L. monocytogenes survives and grows on a range of fresh products including lettuce (Beuchat and Brackett 1990), mixed vegetable salads (Garc ıa-Gimeno et al 1996), green and red peppers and avocado pulp (Salazar et al 2017). Studies such as these have outlined the importance of keeping produce at refrigeration temperatures to slow growth of L. monocytogenes populations, but have also demonstrated that postharvest, L. monocytogenes can survive on the surface of fresh produce for extended periods.…”

Spatiotemporal Variability in Microbial Quality of Western US Agricultural Water Supplies: A Multistate Study

“…While there have been an abundance of studies to model bacterial survival kinetics (Chase et al, 2017, Salazar et al, 2017), transfer dynamics (Atwill et al, 2015), and preharvest risk factors (Pagadala et al, 2015) linked to raw produce consumption (Ibekwe et al, 2005; Pachepsky et al, 2016; Tian et al, 2012), relatively little is known about the potential risk inherent in agricultural water supplies.…”