Growth kinetics of Listeria monocytogenes and spoilage microorganisms in fresh-cut cantaloupe

Modeling the Temperature Effect on the Growth of Uropathogenic Escherichia coli in Sous-Vide Chicken Breast

Uropathogenic Escherichia coli (UPEC) is known to cause 65-75% of human urinary tract infection (UTI) cases. Poultry meat is a reservoir of UPEC, which is suspected to cause foodborne UTIs. In the present study, we aimed to determine the growth potential of UPEC in ready-to-eat chicken breasts prepared by sous-vide processing. Four reference strains isolated from the urine of UTI patients (Bioresource Collection and Research Center [BCRC] 10,675, 15,480, 15,483, and 17,383) were tested by polymerase chain reaction assay for related genes to identify their phylogenetic type and UPEC specificity. A cocktail of these UPEC strains was inoculated into sous-vide cooked chicken breast at 103-4 colony-forming unit (CFU)/g and stored at 4°C, 10°C, 15°C, 20°C, 30°C, and 40°C. Changes in the populations of UPEC during storage were analyzed by a one-step kinetic analysis method using the U.S. Department of Agriculture [USDA] Integrated Pathogen Modeling Program-Global Fit [IPMP-Global Fit]. The results showed that the combination of the no lag phase primary model and the Huang square-root secondary model fitted well with the growth curves to obtain the appropriate kinetic parameters. This combination for predicting UPEC growth kinetics was further validated using it to study additional growth curves at 25°C and 37°C, which showed that the root mean square error, bias factor, and accuracy factor were 0.49-0.59 (log CFU/g), 0.941-0.984, and 1.056-1.063, respectively. In conclusion, the models developed in this study are acceptable and can be used to predict the growth of UPEC in sous-vide chicken breast.

Food safety and food security through predictive microbiology tools: a short review

This article discusses the issues of food safety and food security as a matter of global health. Foodborne illness and deaths caused by pathogens in food continue to be a worldwide problem, with a reported 600 million cases per year, leading to around 420,000 deaths in 2010. Predictive microbiology can play a crucial role in ensuring safe food through mathematical modelling to estimate microbial growth and behaviour. Food security is described as the social and economical means of accessing safe and nutritious food that meets people's dietary preferences and requirements for an active and healthy life. The article also examines various factors that influence food security, including economic, environmental, technological, and geopolitical challenges globally. The concept of food safety is described as a science-based process or action that prevents food from containing substances that could harm human health. Food safety receives limited attention from policymakers and consumers in low- and middle-income countries, where food safety issues are most prevalent. The article also highlights the importance of detecting contaminants and pathogens in food to prevent foodborne illnesses and reduce food waste. Food and Agriculture Organization (FAO), an institution belonging to World Health Organization (WHO) presented calls to action to solve some of the emerging problems in food safety, as it should be a concern of all people to be involved in the pursue of safer food. The guarantee of safe food pertaining to microbiological contamination, as there are different types of active microorganisms in foods, could be obtained using predictive microbiology tools, which study and analyse different microorganisms' behaviour through mathematical models. Studies published by several authors show the application of primary, secondary, or tertiary models of predictive microbiology used for different food products.

Dynamics of Listeria monocytogenes and the microbiome on fresh-cut cantaloupe and romaine lettuce during storage at refrigerated and abusive temperatures

Listeria monocytogenes (Lm) outbreaks and recalls associated with fresh produce in recent years have heightened concerns and demands from industry and consumers to more effectively mitigate the contamination risk of this foodborne pathogen on fresh produce. In this study, the growth of Lm and indigenous bacteria on fresh-cut cantaloupe and romaine lettuce held at refrigerated (4 °C) and abusive (10-24 °C) temperatures was determined by both culture dependent and independent methods. Composition and dynamics of bacterial communities on Lm inoculated and non-inoculated samples were analyzed by 16S rRNA high-throughput sequencing. Fresh-cut cantaloupe provided favorable growth conditions for Lm proliferation (1.7 and >6 log increase at refrigerated and abusive temperatures, respectively) to overtake indigenous bacteria. The Lm population also increased on fresh-cut lettuce, but the growth rate was lower than that of the total mesophilic bacteria, resulting in 0.4 and >2 log increase at refrigerated and abusive temperatures. Microbial diversity of fresh-cut cantaloupe was significantly lower than that of fresh-cut romaine lettuce. The Shannon index of microbial communities on cantaloupe declined after storage, but it was not significantly changed on lettuce samples. Shifts in the bacterial microbiome on cantaloupe were mainly affected by Lm inoculation, while both inoculation and storage temperature played significant roles on lettuce bacterial communities. Multiple indigenous bacteria, including Leuconostoc and Weissella spp., were negatively correlated to Lm abundance on romaine lettuce, and were determined by bioassay as potential anti-listerial species. Data derived from this study contribute to better understanding of the relationship between Lm and indigenous microbiota on fresh-cut produce during storage.

Dynamic kinetic analysis of growth of Listeria monocytogenes in pasteurized cow milk

The objective of this study was to develop a dynamic model for predicting the growth of Listeria monocytogenes in pasteurized cow milk under fluctuating temperature conditions during storage and temperature abuse. Six dynamic temperature profiles that simulated random fluctuation patterns were designed to change arbitrarily between 4 and 30°C. The growth data collected from 3 independent temperature profiles were used to determine the kinetic parameters and construct a growth model combining the primary and secondary models using a 1-step dynamic analysis method. The results showed that the estimated minimum growth temperature and maximum cell concentration were 0.6 ± 0.2°C and 7.8 ± 0.1 log cfu/mL (mean ± standard error), with the root mean square error (RMSE) only 0.3 log cfu/mL for model development. The model and the associated kinetic parameters were validated using the data collected under both dynamic and isothermal conditions, which were not used for model development, to verify the accuracy of prediction. The RMSE of prediction was approximately 0.3 log cfu/mL for fluctuating temperature profiles, and it was between 0.2 and 1.1 log cfu/mL under certain isothermal temperatures (2-30°C). The resulting model and kinetic parameters were further validated using 3 growth curves at 4, 7, and 10°C arbitrarily selected from ComBase (www.combase.cc). The RMSE of prediction was 0.8, 0.4, and 0.5 log cfu/mL, respectively, for these curves. The validation results indicated the predictive model was reasonably accurate, with relatively small RMSE. The model was then used to simulate the growth of L. monocytogenes under a variety of continuous and square-wave temperature profiles to demonstrate its potential application. The results of this study showed that the model developed in this study can be used to predict the growth of L. monocytogenes in contaminated milk during storage.

Growth kinetics of Staphylococcus aureus and background microorganisms in camel milk

Staphylococcus aureus is a common foodborne pathogen that is ubiquitous in nature. Consumption of contaminated foods, such as dairy products, can lead to food poisoning caused by heat-stable staphylococcal toxins that are not easily destroyed during pasteurization. The objective of this study was to investigate the growth kinetics of S. aureus and background microorganisms in camel milk stored at different temperatures between 8 and 43°C using one-step kinetic analysis to estimate the kinetic parameters from the observed growth curves. The growth of S. aureus showed apparent lag, exponential, and stationary phases, whereas no or negligible lag phase was observed for background microorganisms. Data analysis showed that the estimated minimum, optimum, and maximum growth temperatures were 5.9, 42.0, and 49.2°C for S. aureus, and 3.0, 38.6, and 49.2°C for the background microorganisms, respectively. The estimated optimum specific growth rate was higher for S. aureus (1.24 h^-1) than for background microorganisms (0.995 h^-1). This study found that camel milk may inhibit the growth of S. aureus, as it exhibits a lower specific growth rate than that in cow milk or cooked potato. It also has a longer lag phase than that in cow milk at comparable temperature ranges. This unique property is probably related to the presence of some antimicrobial compounds naturally occurring in camel milk. Validation of kinetic parameters and models showed that the root mean square error of prediction was only 0.5 log cfu/mL for S. aureus and background microorganisms, suggesting that the models are reasonably accurate. These models can be used for conducting risk assessments of S. aureus and predicting the general microbiological shelf life of camel milk to prevent foodborne staphylococcal poisoning.

Growth and Survival of Listeria monocytogenes and Salmonella on Whole and Sliced Cucumbers

Cucumbers were associated with four multistate outbreaks of Salmonella in the United States between 2013 and 2016. This study evaluated the fate of Listeria monocytogenes and Salmonella on whole and sliced cucumbers at various storage temperatures. Cucumbers were inoculated with five-strain cocktails of L. monocytogenes or Salmonella, air dried, and stored at 23 ± 2, 4 ± 2, and -18 ± 2°C. Whole and sliced cucumber samples were enumerated on nonselective and selective media at 0, 0.21, 1, 2, 3, and 4 days (23 ± 2°C); 0, 1, 2, 3, 7, 14, and 21 days (4 ± 2°C); and 0, 7, 28, 60, 90, and 120 days (-18 ± 2°C). For Salmonella, additional time points were added at 8 and 17 h (23 ± 2°C) and at 17 h (4 ± 2°C). Population levels were calculated for whole (CFU per cucumber) and sliced (CFU per gram) cucumbers. Both pathogens grew on whole and sliced cucumbers held at ambient temperatures. At 23 ± 2°C, L. monocytogenes and Salmonella populations significantly increased on whole (2.3 and 3.4 log CFU per cucumber, respectively) and sliced (1.7 and 3.2 log CFU/g, respectively) cucumbers within 1 day. Salmonella populations significantly increased on whole and sliced cucumbers after only 5 h (2.1 log CFU per cucumber and 1.5 log CFU/g, respectively), whereas L. monocytogenes populations were not significantly different on whole and sliced cucumbers at 5 h. L. monocytogenes and Salmonella populations survived up to 21 days on refrigerated whole and sliced cucumbers. At 4 ± 2°C, L. monocytogenes populations significantly increased on whole (2.8 log CFU per cucumber) and sliced (2.9 log CFU/g) cucumbers, whereas Salmonella populations significantly decreased on whole (0.6 log CFU per cucumber) and sliced (1.3 log CFU/g) cucumbers over 21 days. Both pathogens survived on frozen whole and sliced cucumbers for at least 120 days. The ability of L. monocytogenes and Salmonella to grow on whole and sliced cucumbers in short amounts of time at ambient temperatures, and to survive on whole and sliced cucumbers past the recommended shelf life at refrigeration temperatures, highlights the need to reduce the likelihood of contamination events throughout the cucumber supply chain.

Infectious Dose of Listeria monocytogenes in Outbreak Linked to Ice Cream, United States, 2015

Listeriosis can occur in susceptible populations when products with low-level contamination are distributed widely.

The relationship between the number of ingested Listeria monocytogenes cells in food and the likelihood of developing listeriosis is not well understood. Data from an outbreak of listeriosis linked to milkshakes made from ice cream produced in 1 factory showed that contaminated products were distributed widely to the public without any reported cases, except for 4 cases of severe illness in persons who were highly susceptible. The ingestion of high doses of L. monocytogenes by these patients infected through milkshakes was unlikely if possible additional contamination associated with the preparation of the milkshake is ruled out. This outbreak illustrated that the vast majority of the population did not become ill after ingesting a low level of L. monocytogenes but raises the question of listeriosis cases in highly susceptible persons after distribution of low-level contaminated products that did not support the growth of this pathogen.

Listeria monocytogenes contamination of ready-to-eat foods and the risk for human health in the EU

Food safety criteria for Listeria monocytogenes in ready-to-eat (RTE) foods have been applied from 2006 onwards (Commission Regulation (EC) 2073/2005). Still, human invasive listeriosis was reported to increase over the period 2009-2013 in the European Union and European Economic Area (EU/EEA). Time series analysis for the 2008-2015 period in the EU/EEA indicated an increasing trend of the monthly notified incidence rate of confirmed human invasive listeriosis of the over 75 age groups and female age group between 25 and 44 years old (probably related to pregnancies). A conceptual model was used to identify factors in the food chain as potential drivers for L. monocytogenes contamination of RTE foods and listeriosis. Factors were related to the host (i. population size of the elderly and/or susceptible people; ii. underlying condition rate), the food (iii. L. monocytogenes prevalence in RTE food at retail; iv. L. monocytogenes concentration in RTE food at retail; v. storage conditions after retail; vi. consumption), the national surveillance systems (vii. improved surveillance), and/or the bacterium (viii. virulence). Factors considered likely to be responsible for the increasing trend in cases are the increased population size of the elderly and susceptible population except for the 25-44 female age group. For the increased incidence rates and cases, the likely factor is the increased proportion of susceptible persons in the age groups over 45 years old for both genders. Quantitative modelling suggests that more than 90% of invasive listeriosis is caused by ingestion of RTE food containing > 2,000 colony forming units (CFU)/g, and that one-third of cases are due to growth in the consumer phase. Awareness should be increased among stakeholders, especially in relation to susceptible risk groups. Innovative methodologies including whole genome sequencing (WGS) for strain identification and monitoring of trends are recommended.

Growth Kinetics of Listeria monocytogenes in Cut Produce

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.

Impact of starch-based emulsions on the antibacterial efficacies of nisin and thymol in cantaloupe juice

The use of antimicrobial compounds to prevent foodborne pathogens from contaminating fresh-cut produce has received broad attentions; however, the applications of these compounds are hindered by their rapid depletion in foods. To prolong their efficacies, the use of delivery systems is essential. In this study, oil-in-water emulsions formed using starch octenyl succinate (starch-OS) were used to stabilize nisin and thymol in cantaloupe juice-containing fluid. Listeria monocytogenes V7 and Salmonella enterica serovar Typhimurium were used as model pathogens to evaluate the antimicrobial activities of nisin and thymol formulations in cantaloupe juice. The results showed that the emulsions had much greater capability to retain nisin and thymol over the storage and displayed much greater effect to inhibit Listeria and Salmonella than non-emulsion, aqueous formulations. Starch-OS based emulsions not only retained nisin and thymol activities separately, but also exhibited their cooperative antibacterial effects.

Fate of Listeria monocytogenes in Fresh Apples and Caramel Apples

An outbreak of listeriosis in late 2014 and early 2015 associated with caramel apples led to questions about how this product became a vector for Listeria monocytogenes. This investigation aimed to determine information about the survival and growth of L. monocytogenes in both fresh apples and caramel apples, specifically examining the effects of site and level of inoculation, inoculum drying conditions, and storage temperature. At a high inoculation level (7 log CFU per apple), L. monocytogenes inoculated at the stem end proliferated on Gala caramel apples at both 5 and 25°C and on Granny Smith caramel apples at 25°C by as much as 3 to 5 log CFU per apple. Fresh apples and caramel apples inoculated at the equatorial surface supported survival but not growth of the pathogen. Growth rates (μmax) for apples inoculated at the stem end, as determined using the Baranyi and Roberts growth model, were 1.64 ± 0.27 and 1.38 ± 0.20 log CFU per apple per day for Gala and Granny Smith caramel apples, respectively, stored at 25°C. At a low inoculation level (3 log CFU per apple), L. monocytogenes inoculated at the stem end and the equatorial surface survived but did not grow on fresh Gala and Granny Smith apples stored at 25°C for 49 days; however, on caramel apples inoculated at the stem end, L. monocytogenes had significant growth under the same conditions. Although certain conditions did not support growth, the pathogen was always detectable by enrichment culture. The inoculation procedure had a significant effect on results; when the inoculum was allowed to dry for 24 h at 5°C, growth was significantly slowed compared with inoculum allowed to dry for 2 h at 25°C. Variation in stick materials did affect L. monocytogenes survival, but these differences were diminished once sticks were placed into caramel apples.

Transfer of Pathogens from Cantaloupe Rind to Preparation Surfaces and Edible Tissue as a Function of Cutting Method

Whole and cut cantaloupes have been implicated as vehicles in foodborne illness outbreaks of norovirus, salmonellosis, and listeriosis. Preparation methods that minimize pathogen transfer from external surfaces to the edible tissue are needed. Two preparation methods were compared for the transfer of Listeria monocytogenes, Salmonella enterica serovar Typhimurium LT2, murine norovirus, and Tulane virus from inoculated cantaloupe rinds to edible tissue and preparation surfaces. For the first method, cantaloupes were cut into eighths, and edible tissue was separated from the rind and cubed with the same knife used to open the cantaloupes. For the second method, cantaloupes were scored with a knife around the circumference sufficient to allow manual separation of the cantaloupes into halves. Edible tissue was scooped with a spoon and did not contact the preparation surface touched by the rind. Bacteria and virus were recovered from the rinds, preparation surfaces, and edible tissue and enumerated by culture methods and reverse transcription, quantitative PCR, respectively. Standard plate counts were determined throughout refrigerated storage of cantaloupe tissue. Cut method 2 yielded approximately 1 log lower recovery of L. monocytogenes and Salmonella Typhimurium from edible tissue, depending on the medium in which the bacteria were inoculated. A slight reduction was observed in murine norovirus recovered from edible tissue by cut method 2. The Tulane virus was detected in approximately half of the sampled cantaloupe tissue and only at very low levels. Aerobic mesophilic colony counts were lower through day 6 of storage for buffered peptone water-inoculated cantaloupes prepared by cut method 2. No differences were observed in environmental contamination as a function of cutting method. Although small reductions in contamination of edible tissue were observed for cut method 2, the extent of microbial transfer underscores the importance of preventing contamination of whole cantaloupes.

Efficacy of Sanitizer Treatments on Survival and Growth Parameters of Escherichia coli O157:H7, Salmonella, and Listeria monocytogenes on Fresh-Cut Pieces of Cantaloupe during Storage

For health reasons, people are consuming fresh-cut fruits with or without minimal processing and, thereby, exposing themselves to the risk of foodborne illness if such fruits are contaminated with bacterial pathogens. This study investigated survival and growth parameters of Escherichia coli O157:H7, Salmonella, Listeria monocytogenes, and aerobic mesophilic bacteria transferred from cantaloupe rind surfaces to fresh-cut pieces during fresh-cut preparation. All human bacterial pathogens inoculated on cantaloupe rind surfaces averaged ∼4.8 log CFU/cm(2), and the populations transferred to fresh-cut pieces before washing treatments ranged from 3 to 3.5 log CFU/g for all pathogens. A nisin-based sanitizer developed in our laboratory and chlorinated water at 1,000 mg/liter were evaluated for effectiveness in minimizing transfer of bacterial populations from cantaloupe rind surface to fresh-cut pieces. Inoculated and uninoculated cantaloupes were washed for 5 min before fresh-cut preparation and storage of fresh-cut pieces at 5 and 10°C for 15 days and at 22°C for 24 h. In fresh-cut pieces from cantaloupe washed with chlorinated water, only Salmonella was found (0.9 log CFU/g), whereas E. coli O157:H7 and L. monocytogenes were positive only by enrichment. The nisin-based sanitizer prevented transfer of human bacteria from melon rind surfaces to fresh-cut pieces, and the populations in fresh-cut pieces were below detection even by enrichment. Storage temperature affected survival and the growth rate for each type of bacteria on fresh-cut cantaloupe. Specific growth rates of E. coli O157:H7, Salmonella, and L. monocytogenes in fresh-cut pieces were similar, whereas the aerobic mesophilic bacteria grew 60 to 80 % faster and had shorter lag phases.

Growth of Salmonella enterica and Listeria monocytogenes on Fresh-Cut Cantaloupe under Different Temperature Abuse Scenarios

Effective cold chain management is a critical component of food safety practice. In this study, we examined the impact of commonly encountered temperature abuse scenarios on the proliferation of Salmonella enterica and Listeria monocytogenes on fresh-cut cantaloupe. Inoculated fresh-cut cantaloupe cubes were subjected to various temperature abuse conditions, and the growth of S. enterica and L. monocytogenes was determined. During 1 week of storage, Salmonella cell counts on fresh-cut cantaloupe increased by -0.26, 1.39, and 2.23 log units at 4 °C (control), 8 °C, and 12 °C (chronic temperature abuse), respectively, whereas that of L. monocytogenes increased by 0.75, 2.86, and 4.17 log units. Under intermittent temperature abuse conditions, where storage temperature fluctuated twice daily to room temperature for 30 min, Salmonella cell count increased by 2.18 log units, whereas that of L. monocytogenes increased by 1.86 log units. In contrast, terminal acute temperature abuses for 2 to 4 h resulted in upwards to 0.6 log unit for Salmonella, whereas the effect on L. monocytogenes was less significant compared with L. monocytogenes on cut cantaloupe stored at 4 °C. Significant deterioration of produce visual quality and tissue integrity, as reflected by electrolyte leakage, was also observed under various temperature abuse conditions.

Predictive modeling for growth of non- and cold-adapted Listeria monocytogenes on fresh-cut cantaloupe at different storage temperatures

The aim of this study was to determine the growth kinetics of Listeria monocytogenes, with and without cold-adaption, on fresh-cut cantaloupe under different storage temperatures. Fresh-cut samples, spot inoculated with a 4-strain cocktail of L. monocytogenes (∼3.2 log CFU/g), were exposed to constant storage temperatures held at 10, 15, 20, 25, or 30 °C. All growth curves of L. monocytogenes were fitted to the Baranyi, modified Gompertz, and Huang models. Regardless of conditions under which cells grew, the time needed to reach 5 log CFU/g decreased with the elevated storage temperature. Experimental results showed that there were no significant differences (P > 0.05) in the maximum growth rate k (log CFU/g h(-1) ) and lag phase duration λ (h) between the cultures of L. monocytogenes with or without previous cold-adaption treatments. No distinct difference was observed in the growth pattern among 3 primary models at various storage temperatures. The growth curves of secondary modeling were fitted on an Arrhenius-type model for describing the relationship between k and temperature of the L. monocytogenes on fresh-cut cantaloupe from 10 to 30 °C. The root mean square error values of secondary models for non- and cold-adapted cells were 0.018, 0.021, and 0.024, and 0.039, 0.026, and 0.017 at the modified Gompertz, Baranyi, and Huang model, respectively, indicating that these 3 models presented the good statistical fit. This study may provide valuable information to predict the growth of L. monocytogenes on fresh-cut cantaloupes at different storage conditions.

PRACTICAL APPLICATION

Listeriosis has occurred and increased along with the increased demand of fresh and fresh-cut fruits and vegetables. This study was conducted to predict the growth of non- and cold-adapted L. monocytogenes on fresh-cut cantaloupe at different temperature using mathematical model. These results can be helpful for risk assessments of L. monocytogenes in fresh-cut cantaloupe. This study provides valuable information to food handlers to choose proper storage temperatures for extending the shelf-life of fresh-cut cantaloupe.

Modeling the growth of Listeria monocytogenes on cut cantaloupe, honeydew and watermelon

A recent outbreak linked to whole cantaloupes underscores the importance of understanding growth kinetics of Listeria monocytogenes in cut melons at different temperatures. Whole cantaloupe, watermelon, and honeydew purchased from a local supermarket were cut into 10 ± 1 g cubes. A four-strain cocktail of L. monocytogenes from food related outbreaks was used to inoculate fruit, resulting in ~10(3) CFU/10 g. Samples were stored at 4, 10, 15, 20, or 25 °C and L. monocytogenes were enumerated at appropriate time intervals. The square root model was used to describe L. monocytogenes growth rate as a function of temperature. The model was compared to prior models for Salmonella and Escherichia coli O157:H7 growth on cut melon, as well as models for L. monocytogenes on cantaloupe and L. monocytogenes ComBase models. The current model predicts faster growth of L. monocytogenes vs. Salmonella and E. coli O157:H7 at temperatures below 20 °C, and agrees with estimates from ComBase Predictor, and a corrected published model for L. monocytogenes on cut cantaloupe. The model predicts ~4 log CFU increase following 15 days at 5 °C, and ∼1 log CFU increase following 6 days at 4 °C. The model can also be used in subsequent quantitative microbial risk assessments.