An Assessment of Listeriosis Risk Associated with a Contaminated Production Lot of Frozen Vegetables Consumed Under Alternative Consumer Handling Scenarios

Abstract

Frozen foods do not support the growth of Listeria monocytogenes (LM) and should be handled appropriately for safety. However, consumer trends regarding preparation of some frozen foods may contribute to the risk of foodborne listeriosis, specifically when cooking instructions are not followed and frozen products are instead added directly to smoothies or salads. A quantitative microbial risk assessment model FFLLoRA (Frozen Food Listeria Lot Risk Assessment) was developed to assess the lot-level listeriosis risk due to LM contamination in frozen vegetables consumed as a ready-to-eat food. The model was designed to estimate listeriosis risk per serving and the number of illnesses per production lot of frozen vegetables contaminated with LM, considering individual facility factors such as lot size, prevalence of LM contamination, and consumer handling prior to consumption. A production lot of 1 million packages with 10 servings each was assumed. When at least half of the servings were cooked prior to consumption, the median risk of invasive listeriosis per serving in both the general and susceptible population was <1.0 × 10−16 with the median (5th, 95th percentiles) predicted number of illnesses per lot as 0 (0, 0) and 0 (0, 1) under the exponential and Weibull-gamma dose-response functions, respectively. In scenarios in which all servings are consumed as ready-to-eat, the median predicted risk per serving was 1.8 × 10−13 and 7.8 × 10−12 in the general and susceptible populations, respectively. The median (5th, 95th percentile) number of illnesses was 0 (0, 0) and 0 (0, 6) for the exponential and Weibull-Gamma models, respectively. Classification tree analysis highlighted initial concentration of LM in the lot, temperature at which the product is thawed, and whether a serving is cooked as main predictors for illness from a lot. Overall, the FFLLoRA provides frozen food manufacturers with a tool to assess LM contamination and consumer behavior when managing rare and/or minimal contamination events in frozen foods. HIGHLIGHTS

Pathogenicity and virulence of Listeria monocytogenes: A trip from environmental to medical microbiology

“…Despite frozen foods do not support the growth of L. monocytogenes , consumption of this type of food may contribute to the risk of listeriosis, mainly when it is added directly (e.g. to salads or smoothies) [ 61 ]. L. monocytogenes adaptation mechanisms to cold and their consequences are described in the next sections.…”

Exposure assessment suggests some cytotoxicBacillus cereusgroup genotypes can grow over 3 logs in HTST milk throughout the shelf life at temperature abuse conditions

“…For example, a prediction that the risk of causing a single human case is substantially below 1% may be more valuable than the type of exposure risk that is provided as an output by our model. This type of approach has previously been used in a risk assessment that was designed to help with decision making on lots of produce that may be contaminated with Listeria monocytogenes (Zoellner et al, 2019). However, using the exposure assessment reported here, prediction of human illness cases that may be caused by a lot is currently impossible due to the lack of a universally applicable dose-response relationship that will allow us to predict the likelihood of B. cereus toxico-infection per serving and estimate the number of cases within the population (Notermans et al, 1997, Ačai et al, 2014, Lewin et al, 2019).…”

High‐pressure pasteurization of low‐acid chilled ready‐to‐eat food

“…Multiple listeriosis outbreaks have been linked to the consumption of not‐ready‐to‐eat food products (Francis et al., 1999). No regulatory limits for L. monocytogenes apply to frozen not‐ready‐to‐eat products due to the assumption that consumers will fully cook the product before consumption (Zoellner et al., 2019). However, frozen vegetables, such as peas, are consumed without cooking, which can be used for smoothies and dips (Zoellner et al., 2019) or added to salad after thawing although they are not considered to be RTE (Magdovitz et al., 2020).…”

“…No regulatory limits for L. monocytogenes apply to frozen not‐ready‐to‐eat products due to the assumption that consumers will fully cook the product before consumption (Zoellner et al., 2019). However, frozen vegetables, such as peas, are consumed without cooking, which can be used for smoothies and dips (Zoellner et al., 2019) or added to salad after thawing although they are not considered to be RTE (Magdovitz et al., 2020). Therefore, many global recalls and outbreaks of listeriosis have been associated with frozen foods including vegetables such as corn, spinach, and green beans although food products after freezing do not support the growth of L. monocytogenes (European Food Safety Authority & European Centre for Disease Prevention and Control, 2018).…”