Consumer home refrigeration practices: results of a web-based survey

Phenotypic and genomic characterizations of Klebsiella pneumoniae ssp. pneumoniae and Rahnella inusitata strains reveal no clear association between genetic content and ropy phenotype

Ropy defect of pasteurized fluid milk is a type of spoilage which manifests itself by an increased viscosity, slimy body, and string-like flow during pouring. This defect has, among other causes, been attributed to the growth, proliferation and exopolysaccharide production by coliform bacteria, which are most commonly introduced in milk as post-pasteurization contaminants. As we identified both Klebsiella pneumoniae ssp. pneumoniae and Rahnella inusitata that were linked to a ropy defect, the goal of this study was to characterize 3 K. pneumoniae ssp. pneumoniae strains and 2 R. inusitata for (1) their ability to grow and cause ropy defect in milk at 6°C and 21°C and to (2) probe the genetic basis for observed ropy phenotype. Although all K. pneumoniae ssp. pneumoniae and R. inusitata strains showed net growth of >4 log10 over 48 h in UHT milk at 21°C, only R. inusitata strains displayed growth during 28-d incubation period at 6°C (>6 log10). Two out of 3 K. pneumoniae ssp. pneumoniae strains were capable of causing the ropy defect in milk at 21°C, as supported by an increase in the viscosity of milk and string-like flow during pouring; these 2 strains were originally isolated from raw milk. Only one R. inusitata strains was able to cause the ropy defect in milk; this strain was able to cause the defect at both 6°C and 21°C, and was originally isolated from a pasteurized milk. These findings suggest that the potential of K. pneumoniae ssp. pneumoniae and R. inusitata to cause ropy defect in milk is a strain-dependent characteristic. Comparative genomics provided no definitive answer on genetic basis for the ropy phenotype. However, for K. pneumoniae ssp. pneumoniae, genes rffG, rffH, rfbD, and rfbC involved in biosynthesis and secretion of enterobacterial common antigen (ECA) could only be found in the 2 strains that produced ropy defect, and for R. inusitata a set of 2 glycosyltransferase- and flippase genes involved in nucleotide sugar biosynthesis and export could only be identified in the ropy strain. Although these results provide some initial information for potential markers for strains that can cause ropy milk, the relationship between genetic content and ropiness in milk remains poorly understood and merits further investigation.

Molecular characterization and in vivo pathogenicity study of Listeria monocytogenes isolated from fresh and frozen local and imported fish in Jordan

Background:

Listeria monocytogenes (L. monocytogenes) is a serious zoonotic and food transmitted human pathogen causing meningitis and abortions. Several outbreaks of listeriosis have been associated with the consumption of ready-to-eat food products; dairy, meat, fish, and contaminated fruits and vegetables worldwide.

Aim:

This study was designed to detect and characterize L. monocytogenes isolated from local and imported fish in Jordan.

Methods:

A total of 170 fish (70 local and 100 imported), of which 140 fresh and 30 frozen samples were used in this study. Listeria monocytogenes was cultured and initially identified using conventional microbiological methods. For confirmation and serotyping of the L. monocytogenes isolates, PCR techniques were used. Using oral and intraperitoneal administration, mice were used to determine the pathogenicity and LD₅₀ of the isolated L. monocytogenes.

Results:

A total of 72 Listeria spp. isolates were cultured from fish. Of those, 24 were positively identified as L. monocytogenes. Other strains of Listeria spp. were L. ivanovii (21), L. innocua (11), and L. grayi (16). Serotyping of the L. monocytogenes indicated that 14 isolates belonged to the 1/2b, 3b serotypes whereas 10 isolates belonged to the 4a and 4c serotypes. All isolates were virulent to mice with an LD₅₀ dose ranging from 3 × 10¹⁰ CFU/ml to 3 × 10^7.5 CFU/ml. All the virulent isolates belonged to the serotype 1/2b. Histopathologically, dead mice showed multiple necrotic lesions in the liver and spleen.

Conclusion:

Results of this study showed the presence of potentially pathogenic L. monocytogenes in fresh and frozen, local, and imported fish in Jordan. Strict monitoring and quality control regulatory measures must be adopted to prevent future outbreaks of food poisoning associated with fish consumption.

Safe Food Handling Advice Provided on Question-and-Answer Web Sites Is Inconsistent

OBJECTIVE

To determine the accuracy of information about safe food handling posted on online question-and-answer (Q&A) Web sites and forums.

DESIGN

A retrospective study was conducted to analyze answers to questions posted on 4 Q&A platforms (Reddit, Yahoo! Answers, Quora, and Stack Exchange) employing a structured coding form. Questions were identified from November 2018 to May 2019 using an iterative search.

PARTICIPANTS

Users of online Q&A platforms.

MAIN OUTCOME MEASURE

Answer accuracy (incorrect, partially correct, or correct in relation to government guidelines).

ANALYSIS

A multivariable ordinal regression model was developed to identify factors associated (at the P < .01 level) with answer accuracy.

RESULTS

Questions (n = 160) were posted from 2006 to 2019. Of 625 answers to these questions, 41% were classified as correct, and 20% as partially correct. Answer accuracy differed among the 4 platforms. Answers to questions about adequate cooking (odds ratio [OR] = 0.29, 95% confidence interval [CI], 0.17-0.49, P < .001) and time-temperature control (OR = 0.33, 95% CI, 0.21-0.51, P < .001) constructs were less likely to be correct than answers to other questions. Top-rated answers were more likely to be correct than other answers (OR = 2.01, 95% CI, 1.40-2.90, P < .001).

CONCLUSIONS AND IMPLICATIONS

The accuracy of food safety information exchanged on online Q&A platforms is inconsistent. Enhanced food safety promotion and education interventions on these platforms are warranted.

Food Consumer Behavior and Salmonella Exposure Self-Perception in the Central Region of Mexico

In Mexico, there is limited information regarding food consumer behaviors at home. The knowledge of food consumption and food handling practices can help to determine more realistically the exposure to different hazards, such as Salmonella spp. on the population. The main goal of this study was to characterize the food consumption habits of five food groups (fruits and vegetables, fresh meat, dairy products, processed meat products, and seafood), food handling practices, and Salmonella exposure self-perception of the population of the central region of Mexico using an online survey. A total of 1,199 surveys were analyzed. The group of fruits and vegetables is the most consumed and one of the most related to the consumer self-perception of suffering from salmonellosis. Mexican consumers regularly use refrigeration as the principal food storage method for the five food groups (42.2% to 90.8%), and generally, they store the products between 2 and 3 days (26.5% to 38.1%). A total of 86.4% of consumers reported that they always wash their hands prior to food preparation. A total of 16.9% and 13.0% use the same cutting board and knife, respectively, to cut more than one product without applying sanitization. Men, people between 20 and 24 years, and people between 60 and 64 years, had the highest risk food handling practices at home. Finally, age (P < 0.0001), education level (P = 0.0004), and suffering from gastrointestinal diseases (P = 0.0005) showed significant effects with self-perception of having salmonellosis. PRACTICAL APPLICATION: Data presented in this study could be used in future risk and exposure assessment research to evaluate the public health risk from the consumption of contaminated food. In addition, it could be used by government agencies to design education campaigns in food safety area.

Motivators and Barriers to Cooking and Refrigerator Thermometer Use among Consumers and Food Workers: A Review

Temperature control prevents the rapid growth of foodborne pathogens during food storage and assures adequate heating to destroy pathogens prior to consumption. The use of thermometers is a recognized best practice among consumer and food worker guidelines; however, compliance with this recommendation is quite low. Eighty-five studies from the past 21 years were reviewed and an analyzed for the knowledge, attitudes, and behaviors associated with thermometer use and the motivators and barriers to cooking and refrigerator thermometer use among consumers and food workers. Barriers to thermometer were categorized into two major groups: "the belief that a thermometer is not necessary" and "the difficulty of selecting and using a thermometer." Each group has its unique aspects. Four barriers were recognized in the "not necessary" group: (i) preference for alternative techniques, (ii) mainstream media and food professionals seldom serve as role models and often negate the need for food thermometers, (iii) limited awareness of potential health issues associated with current practices, and (iv) limited knowledge and awareness related to thermometer usage for specific food groups. Six barriers were recognized in the "difficult to select and use" group: (i) difficulties in selecting the type of food thermometers, (ii) availability of food thermometers, (iii) lack of skills related to the usage of food thermometers, (iv) limited knowledge related to endpoint temperatures, (v) inability to calibrate food thermometers, and (vi) lack of knowledge about food thermometer cleaning and sanitation. These findings will facilitate the development and adoption of effective strategies to increase thermometer use and increase food safety education efficacy with a positive impact on public health.

Pseudomonas fluorescens group bacterial strains are responsible for repeat and sporadic postpasteurization contamination and reduced fluid milk shelf life

Postpasteurization contamination (PPC) of high temperature, short time-pasteurized fluid milk by gram-negative (GN) bacteria continues to be an issue for processors. To improve PPC control, a better understanding of PPC patterns in dairy processing facilities over time and across equipment is needed. We thus collected samples from 10 fluid milk processing facilities to (1) detect and characterize PPC patterns over time, (2) determine the efficacy of different media to detect PPC, and (3) characterize sensory defects associated with PPC. Specifically, we collected 280 samples of high temperature, short time-pasteurized milk representing different products (2%, skim, and chocolate) and different fillers over 4 samplings performed over 11 mo at each of the 10 facilities. Standard plate count (SPC) as well as total GN, coliform, and Enterobacteriaceae (EB) counts were performed upon receipt and after 7, 10, 14, 17, and 21 d of storage at 6°C. We used 16S rDNA sequencing to characterize representative bacterial isolates from (1) test days with SPC >20,000 cfu/mL and (2) all samples with presumptive GN, coliforms, or EB. Day-21 samples were also evaluated by a trained defect judging panel. By d 21, 226 samples had SPC >20,000 cfu/mL on at least 1 d of shelf life; GN bacteria were found in 132 of these 226 samples, indicating PPC. Crystal violet tetrazolium agar detected PPC with the greatest sensitivity. Spoilage due to PPC was predominantly associated with Pseudomonas (isolated from 101 of the 132 samples with PPC); coliforms and EB were found in 27 and 37 samples with spoilage due to PPC, respectively. Detection of Pseudomonas and Acinetobacter was associated with lower flavor scores; coagulated, fruity fermented, and unclean defects were more prevalent in d-21 samples with PPC. Repeat isolation of Pseudomonas fluorescens group strains with identical partial 16S rDNA sequence types was observed in 8 facilities. In several facilities, specific lines, products, or processing days were linked to repeat product contamination with Pseudomonas with identical sequence types. Our data show that PPC due to Pseudomonas remains a major challenge for fluid milk processors; the inability of coliform and EB tests to detect Pseudomonas may contribute to this. Our data also provide important initial insights into PPC patterns (e.g., line-specific contamination), supporting the importance of molecular subtyping methods for identification of PPC sources.

Effect of cold chain interruptions on the shelf-life of fluid pasteurised skim milk at the consumer stage

Abstract This study aimed to verify the effect of time and temperature abuse on bacterial numbers in fluid pasteurized skim milk by simulating the real-life scenario, which usually occurs when cold chain is interrupted by consumers prior to consumption that affect the shelf-life of milk. Total three trials were carried out in this study. Thermal abuse was simulated with temperature fluctuations from 5 °C. In the first trial, the information about holding the milk samples for 8 hours at three different temperatures of 15 °C, 20 °C and 25 °C was obtained using a data logger to predict the effect of temperature abuse on the milk microbial quality. Further, in the second and third trial, the effect of temperature abuse on bacterial numbers was examined by holding milk at 5 °C and then shifts temperature to 25 °C for 8 h and 6 h. The pH was monitored during storage. The total bacterial count was examined by the Standard Plate Count (SPC). The mean air temperature had the greatest impact on milk temperature. It took 3.0 h, 3.9 h and 4.2 h to warm up when exposed to the temperatures of 15 °C, 20 °C and 25 °C, respectively. The holding time of 8 h at 25 °C showed that bacterial numbers (1 x 105 CFU mL-1) were higher after 14 days of storage, but control samples at 5 °C (< 1 x 104 CFU mL-1) were still within the acceptable level (5 x 104 CFU mL-1). A holding time of 6 h at 25 oC showed much higher bacterial numbers (1 x 109 CFU mL-1) compared to control samples (1 x 107 CFU mL-1) which were held at 5 °C for 11 days. The pH of the milk decreased with increasing bacterial growth during the extended storage time. The results show that temperature abuse has a significant effect on milk microbial stability and shelf life. It is important to maintain the milk temperature at 5 °C or less as the bacterial growth directly depend on increasing temperature and holding time, which pose the potential risk of microbial hazards leading to foodborne illness. Thus, consumers must understand the factors associated with the safe handling of milk to keep it safe to use before the expiry date.

Food Leftover Practices among Consumers in Selected Countries in Europe, South and North America

Foodborne illnesses may be related to many food production factors with home practices of consumers playing an important role in food safety. Consumer behavior for handling food leftovers has been studied, however little work on comparisons among countries has been published. The objective of this study was to investigate home food leftover practices of people from North American, South American, and European countries. Surveys were conducted with approximately 100 or more consumers in Argentina, Colombia, the United States, Estonia, Italy, Russia, and Spain. The participants responded to questions related to the length of time different types of food leftovers; such as meat, fresh salads, or restaurant dishes would be kept refrigerated or would be left at room temperature before refrigeration. Researchers also investigated how consumers would determine if the food was still safe for consumption. Potentially risky behaviors were observed in all seven countries. For instance, 55.8% of Estonians, 25% of Russians and 25.8% of Argentinean participants left food out at room temperature for several hours before storing in the refrigerator. Furthermore, 25%-29% of Colombian, Estonian, and Spanish consumers would look, smell, and taste leftovers to determine its probable safety. Correct handling of leftovers is an important aspect of consumer food safety. Although the surveys cannot be representative of all consumers in each country, they do provide an initial overview of comparative practices for handling leftovers among different countries. This provides government and educators with information on potential universal and unique consumer food safety issues related to handling leftover foods among various countries.

Development of the Consumer Refrigerator Safety Questionnaire: A Measure of Consumer Perceptions and Practices

Food preparation and storage behaviors in the home deviating from the "best practice" food safety recommendations may result in foodborne illnesses. Currently, there are limited tools available to fully evaluate the consumer knowledge, perceptions, and behavior in the area of refrigerator safety. The current study aimed to develop a valid and reliable tool in the form of a questionnaire, the Consumer Refrigerator Safety Questionnaire (CRSQ), for assessing systematically all these aspects. Items relating to refrigerator safety knowledge (n =17), perceptions (n =46), and reported behavior (n =30) were developed and pilot tested by an expert reference group and various consumer groups to assess face and content validity (n =20), item difficulty and consistency (n =55), and construct validity (n =23). The findings showed that the CRSQ has acceptable face and content validity with acceptable levels of item difficulty. Item consistency was observed for 12 of 15 in refrigerator safety knowledge. Further, all 5 of the subscales of consumer perceptions of refrigerator safety practices relating to risk of developing foodborne disease showed acceptable internal consistency (Cronbach's α value > 0.8). Construct validity of the CRSQ was shown to be very good (P = 0.022). The CRSQ exhibited acceptable test-retest reliability at 14 days with the majority of knowledge items (93.3%) and reported behavior items (96.4%) having correlation coefficients of greater than 0.70. Overall, the CRSQ was deemed valid and reliable in assessing refrigerator safety knowledge and behavior; therefore, it has the potential for future use in identifying groups of individuals at increased risk of deviating from recommended refrigerator safety practices, as well as the assessment of refrigerator safety knowledge and behavior for use before and after an intervention.

Short communication: Postpasteurization hold temperatures of 4 or 6°C, but not raw milk holding of 24 or 72 hours, affect bacterial outgrowth in pasteurized fluid milk

As fluid milk processors continue to reduce microbial spoilage in fluid milk through improved control of postpasteurization contamination and psychrotolerant sporeformer outgrowth, it is necessary to identify strategies to further improve the quality and extend the shelf life of fluid milk products that are high-temperature, short-time pasteurized. Solutions that optimize product quality, and are economically feasible, are of particular interest to the dairy industry. To this end, this study examined the effects of raw milk holding time and temperature of pasteurized milk storage over shelf life on bacterial growth. In 3 independent replicates, raw milk was stored for 24 and 72 h before pasteurization at 76°C for 25s and then incubated at 3 different storage conditions: (1) 4°C for 21d; (2) 4°C for the first 48 h, then 6°C for the duration of the 21-d shelf life; or (3) 6°C for 21d. Total bacteria counts were assessed initially and on d 7, 14, and 21. No substantial difference in bacterial growth over shelf life was observed between samples processed from raw milk held for 24 versus 72 h. A significantly lower bacterial load was seen at d 21 after pasteurization in samples held at 4°C, versus 4°C for the first 48 h followed by 6°C for the duration of the 21-d shelf life and samples held at 6°C for 21d. This work demonstrates the importance of maintaining control of the fluid milk cold chain throughout postpasteurization, transportation, and retail storage on fluid milk microbial quality.

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.

Acute oral safety study of sodium caseinate glycosylated via maillard reaction with galactose in rats

In order to potentially use sodium caseinate (SC) glycated with galactose (Gal) in the food industry as a new functional ingredient with proved technological and biological properties, an evaluation of oral acute toxicity has been carried out. An acute safety study with SC-Gal glycoconjugates in the Wistar rat with a single oral gavage dose of 2,000 mg/kg of body weight was conducted. The SC-Gal glycoconjugates were well tolerated; no adverse effects or mortality was observed during the 2-week observation period. No abnormal signs, behavioral changes, body weight changes, or alterations in food and water consumption occurred. After this period, no changes in hematological and serum chemistry parameters, organ weights, or gross pathology or histopathology were detected. It was concluded that SC-Gal glycoconjugates obtained via the Maillard reaction were well tolerated in rats at an acute oral dose of 2,000 mg/kg of body weight. The SC-Gal glycoconjugates have a low order of acute toxicity, and the oral 50 % lethal dose for male and female rats is in excess of 2,000 mg/kg of body weight.

Behavioral risk factors associated with listeriosis in the home: a review of consumer food safety studies

Listeria monocytogenes causes human listeriosis, which is associated with the highest hospitalization and mortality rates of all foodborne illnesses. In recent years, the incidence of listeriosis has doubled in Europe, almost exclusively among older adults (≥ 60 years of age). Food safety factors associated with increased risk of listeriosis include lack of adherence to "use by" dates and ineffective refrigerated storage of foods. Consequently, older adult consumers' implementation of safe food practices should be evaluated. This article is a review of consumer food safety cognitive and behavioral data relating to risk factors associated with listeriosis in the home as reported in 165 consumer food safety studies. Overall, only 41% of studies included assessment of consumer cognitive or behavioral data associated with listeriosis; of these studies 59% included data on safe refrigeration, 54% included data on storage time for opened ready-to-eat foods, and 49% included data on adherence to use-by dates. In most (83%) of the studies, survey-based data collection methods (questionnaires/interviews) were used; thus, the majority of findings were based on self-report (74%) and knowledge (44%). Observation (31%) and focus groups (12%) were less commonly used, resulting in a lack of actual behaviors and attitudinal data relating to listeriosis risk factors. Only 7% of studies included food safety data for older adults. Although older adults may fail to implement recommended practices, this review reveals a need for in-depth research to determine food safety attitudes and actual behaviors of older adults in conjunction with knowledge and selfreport of practices linked to increased risks of listeriosis. Such data combined with review findings would inform targeted food safety education to reduce risks associated with listeriosis in the home.

Food safety practices among Norwegian consumers

An informed consumer can compensate for several potential food safety violations or contaminations that may occur earlier in the food production chain. However, a consumer can also destroy the work of others in the chain by poor food handling practices, e.g., by storing chilled ready-to-eat foods at abusive temperatures. To target risk-reducing strategies, consumer groups with high-risk behavior should be identified. The aim of this study was to identify demographic characteristics associated with high-risk food handling practices among Norwegian consumers. More than 2,000 randomly selected Norwegian consumers were surveyed, and the results were analyzed with a risk-based grading system, awarding demerit points for self-reported food safety violations. The violations were categorized into groups, and an ordinary multiple linear regression analysis was run on the summarized demerit score for each group and for the entire survey group as a whole. Young and elderly men were identified as the least informed consumer groups with the most unsafe practices regarding food safety. Single persons reported poorer practices than those in a relationship. People with higher education reported poorer practices than those with lower or no education, and those living in the capital of Norway (Oslo) reported following more unsafe food practices than people living elsewhere in Norway. Men reported poorer food safety practices than women in all categories with two exceptions: parboiling raw vegetables before consumption and knowledge of refrigerator temperature. These findings suggest that risk-reducing measures should target men, and a strategy is needed to change their behavior and attitudes.

Application of Hazard Analysis and Critical Control Point Methodology and Risk-Based Grading to Consumer Food Safety Surveys

Traditionally, consumer food safety survey responses have been classified as either “right” or “wrong” and food handling practices that are associated with high risk of infection have been treated in the same way as practices with lower risks. In this study, a risk-based method for consumer food safety surveys has been developed, and HACCP (hazard analysis and critical control point) methodology was used for selecting relevant questions. We conducted a nationally representative Web-based survey (n = 2,008), and to fit the self-reported answers we adjusted a risk-based grading system originally developed for observational studies. The results of the survey were analyzed both with the traditional “right” and “wrong” classification and with the risk-based grading system. The results using the two methods were very different. Only 5 of the 10 most frequent food handling violations were among the 10 practices associated with the highest risk. These 10 practices dealt with different aspects of heat treatment (lacking or insufficient), whereas the majority of the most frequent violations involved storing food at room temperature for too long. Use of the risk-based grading system for survey responses gave a more realistic picture of risks associated with domestic food handling practices. The method highlighted important violations and minor errors, which are performed by most people and are not associated with significant risk. Surveys built on a HACCP-based approach with risk-based grading will contribute to a better understanding of domestic food handling practices and will be of great value for targeted information and educational activities.

Detection of airborne psychrotrophic bacteria and fungi in food storage refrigerators

The purpose of this study was to determine the microbiological air quality (psychrotrophic bacteria and airborne fungi) and distribution of fungi in different types of ready-to-eat (RTE) food-storage refrigerators (n=48) at selected retail stores in the city of Edirne, Turkey. Refrigerators were categorized according to the type of RTE food-storage: meat products, vegetables, desserts, or a mix of food types. Microbiological quality of air samples was evaluated by using a Mas-100 Eco Air Sampler. Four refrigerators (all containing meat products, 8.3%) produced air samples with undetectable microorganisms. The highest detected mean value of airborne psychrotrophic bacteria and fungi was 82.3 CFU/m³ and 54.6 CFU/m³, respectively and were found in mixed-food refrigerators. The dominant airborne fungal genera found were Penicillium (29.0%), Aspergillus (12.0%), Mucor (9%), Cladosporium (8%), Botyrtis (7%), and Acremonium (6%). By definition, RTE food does not undergo a final treatment to ensure its safety prior to consumption. Therefore, ensuring a clean storage environment for these foods is important to prevent food-borne disease and other health risks.

Estimating parametric distributions of storage time and temperature of ready-to-eat foods for U.S. households

Home refrigeration temperatures and product storage times are important factors for controlling the growth of Listeria monocytogenes in refrigerated ready-to-eat foods. In 2005, RTI International, in collaboration with Tennessee State University and Kansas State University, conducted a national survey of U.S. adults to characterize consumers' home storage and refrigeration practices for 10 different categories of refrigerated ready-to-eat foods. No distributions of storage time or refrigeration temperature were presented in any of the resulting publications. This study used classical parametric survival modeling to derive parametric distributions from the RTI International storage practices data set. Depending on the food category, variability in product storage times was best modeled using either exponential or Weibull distributions. The shape and scale of the distributions varied greatly depending on the food category. Moreover, the results indicated that consumers tend to keep a product that is packaged by a manufacturer for a longer period of time than a product that is packaged at retail. Refrigeration temperatures were comparable to those previously reported, with the variability in temperatures best fit using a Laplace distribution, as an alternative to the empirical distribution. In contrast to previous research, limited support was found for a correlation between storage time and temperature. The distributions provided in this study can be used to better model consumer behavior in future risk assessments.

Precut prepackaged lettuce: a risk for listeriosis?

The most recent outbreaks of listeriosis have been traced back to contaminated ready-to-eat (RTE) poultry and meat products. However, Listeria monocytogenes can be isolated from every food group, including fresh vegetables. This review is focused on one of the most popular RTE vegetable products, precut prepackaged lettuce. The available literature concerning Listeria contamination of vegetables is reviewed, and possible reasons why no recent outbreaks or sporadic cases of listeriosis due to contaminated precut prepackaged lettuce are explored.