Search

•Log transformation of time for 5 log reduction was approximately normal.•Temperature and pH significantly (p < 1E−6) affected time for 5-log decline of O157:H7.•Percent water significantly (p < 1E−8) affected time for 5-log decline of Salmonella.•Temperature significantly (p < 1E−3) affected time for 5-log decline of L. mono.•Temperature was the only factor significantly affecting the survival of all 3 pathogens.

It is estimated that one in five cases of foodborne illnesses is acquired in the home. However, how pathogens move throughout a kitchen environment when consumers are preparing food is not well characterized. The purpose of this study was to determine the prevalence and degree of cross-contamination across a variety of kitchen surfaces during a consumer meal preparation event. Consumers (n= 371) prepared a meal consisting of turkey patties containing the bacteriophage MS2 as a tracer organism and a ready-to-eat lettuce salad. Half were shown a video on proper thermometer use before the trial. After meal preparation, environmental sampling and detection were performed to assess cross-contamination with MS2. For most surfaces, positivity did not exceed 20%, with the exception of spice containers, for which 48% of the samples showed evidence of MS2 cross-contamination. Spice containers also had the highest MS2 concentrations, at a mean exceeding 6 log viral genome equivalent copies per surface. The high level of MS2 on spice containers drove the significant differences between surfaces, suggesting the significance of spice containers as a vehicle for cross-contamination, despite the absence of previous reports to this effect. The thermometer safety intervention did not affect cross-contamination. The efficiency of MS2 transfer, when expressed as a percentage, was relatively low, ranging from an average of 0.002 to 0.07%. Quantitative risk assessment work using these data would aid in further understanding the significance of cross-contamination frequency and efficiency. Overall, these data will help create more targeted consumer messaging to better influence consumer cross-contamination behaviors.

Fresh cucumbers have been linked to multistate outbreaks of salmonellosis in the United States. Cutting, slicing, shredding, or peeling can transfer pathogens from the surface of fresh produce to the edible flesh portion through tools or hands. Different nonpathogenic surrogates have been used in various intervention studies to predict Salmonellabehavior. Little is known about the degree to which pathogens or their surrogates can transfer from the surface of fresh produce to edible flesh during peeling. This study quantifies the transfer of SalmonellaNewport from the surface of cucumber to the edible flesh portion or peeler during peeling and evaluates Enterobacter aerogenesB199A, as well as native mesophilic microbiota, as surrogates for Salmonellatransfer. Cucumbers were dip inoculated with SalmonellaNewport or E. aerogenesat 7 log CFU per cucumber. Half of each inoculated cucumber was hand peeled by using a sterilized peeler, resulting in four separate samples (unpeeled half, edible flesh half, removed peel, and used peeler) to quantify bacterial transfer. Most (>95%) of inoculated E. aerogenes, Salmonella,or native mesophilic microbiota generally remained associated with the peel during peeling. E. aerogenestransfer to cucumber flesh ranged from 0.02 to 12.9%, while transfer to the peeler ranged from 0.01 to 6.6%. Salmonellato cucumber flesh ranged from 0 to 0.6%, while transfer to the peeler ranged from 0 to 2.2%. Native microflora transfer to cucumber flesh ranged from 0.02 to 3.7%, while transfer to the peeler ranged from 0.04 to 3.7%. The log percent transfer of E. aerogenesat 24 h, as well as several shorter times, was not significantly different (P> 0.05) from that of Salmonellatransferred to the edible flesh portion or peeler during peeling. E. aerogenesB199A may be a useful surrogate for Salmonellain cross-contamination studies and may help guide future risk management efforts to reduce pathogen risk associated with fresh cucumbers.

Wheat flour has been implicated in recalls and outbreaks linked to Salmonellaand pathogenic Escherichia coli. An instructional online video posted on a popular YouTube channel with over 20 million subscribers claimed that safe raw cookie dough could be made from flour baked in a household oven at 177°C (350°F) for 5 min, but no evidence in support of that claim was provided. This study was conducted to assess thermal inactivation of two Salmonellastrains, as well as Enterobacter aerogenesand Pantoea dispersain wheat flour during home oven baking. Wheat flour was inoculated with SalmonellaEnteritidis PT 30, SalmonellaTyphimurium PT 42, or their potential surrogates at high concentrations (4.8 to 6.1 log CFU/g) before baking in a consumer-style convection oven (toaster oven) at 149, 177, and 204°C (300, 350, or 400°F) for up to 7 min. Flour was heated in an aluminum tray, with a maximum depth of ∼2 cm. Heated wheat flour samples (5 g each) were enumerated in triplicate, and the microbial concentration was expressed in log CFU per gram. Thermal profiles of the geometric center of the wheat flour pile and air in the oven during the baking were recorded. Water activity of wheat flour samples was also measured before and after baking. The water activity of wheat flour decreased, as baking temperature and time increased. Water activity values ranged from 0.30 to 0.06 after 7 min, as oven temperature increased from 149 to 204°C. Thermal inactivation kinetics were linear until counts approached the limit of detection for all microorganisms. D-values for Salmonellaand potential surrogate strains ranged from 1.86 to 2.13 min at 149°C air temperature, 1.66 to 1.92 min at 177°C air temperature, and 1.12 to 1.38 min at 204°C air temperature. Both Salmonellastrains and surrogates showed similar inactivation patterns. Baking of wheat flour in household toaster ovens has potential as an inactivation treatment of pathogenic bacteria in consumer homes, despite its low water activity.

Recent multistate outbreaks of salmonellosis linked to fresh cucumbers underscore the importance of understanding Salmonellabehavior on cucumbers under different storage conditions. No validated models that describe the impact of environmental factors on the growth of Salmonellaon sliced cucumbers currently exist. This study developed mathematical models to predict the growth of Salmonellaon sliced cucumbers at different temperature and relative humidity (RH) conditions. Sliced cucumbers were inoculated with a four-strain cocktail of Salmonellaand placed in desiccators containing a saturated salt solution to create controlled RH environments (∼15, 50, and 100% RH) at 7, 14, and 21°C for up to 120 h. Predictive models were developed by using the Baranyi and Roberts equation as a primary model, and estimated kinetic parameters were fitted into a square root (or Ratkowsky) equation for secondary models. The maximum growth rates for Salmonellaon sliced cucumbers depended on temperature but not RH. The square root model for Salmonellagrowth was √μ= 0.0297 × (T− 6.5185), with a high R2value (0.98). The models in this study will be useful for future microbial risk assessments and predictions of Salmonellabehavior in the cucumbers to manage the risk of Salmonellaon sliced cucumbers.

•Food depth had a highly significant effect (p = 8.90E−08) on cooling rate.•Use of an ice bath or ice wand had a significant effect (p < 0.005) on cooling rate.•Most foods cooled with ice wand and ice bath met the recommended cooling rate.•Slowly cooling foods were partially or wholly covered or were cooled at >5 °C.•Cooling foods with a depth of <5.1 cm (2 in.) had little predicted pathogen growth.

Listeria monocytogeneshas shown the ability to grow on fresh uncut produce; however, the factors that control growth are not well understood. Peer-reviewed journal articles (n= 29) meeting the inclusion criteria and related to the growth of L. monocytogeneson fresh produce were found through university library databases and Google Scholar searches. Growth models were fit to each of the extracted 130 data sets to estimate log CFU per day rates of growth by using the DMFit tool. Multiple linear stepwise regression models for factors influencing growth rate were developed using R software. Factors included were temperature, nutrient level of inoculation buffer, initial cell concentration, final cell concentration, inoculation method, container permeability, and surface characteristics. The full model produced adjusted R2, Akaike information criterion, and root mean square error values of 0.41, 488, and 1.61, respectively. Stepwise regression resulted in a reduced model with parameters for incubation temperature, inoculation buffer type, initial and final cell concentrations, container characteristics, and produce surface characteristics. Model fit statistics improved slightly in the reduced model. A further reduced three-parameter model included storage temperature and initial and final cell concentrations, with interaction terms. This three-parameter model had adjusted R2, Akaike information criterion, and root mean square error values of 0.66, 417, and 1.24, respectively. Incubation temperature (P= 1.00E−09) initial cell concentration (P= 3.05E−12), and final cell concentration (P= 4.17E−09) all had highly significant effects on maximum growth rate. Our findings show the importance of inoculum concentration and produce microbial carrying capacity on the estimated growth rate and highlight the overall importance that temperature has on growth rate. Future experiments should consider initial inoculum concentration carefully when conducting growth studies for L. monocytogeneson whole produce.

Listeria monocytogenescauses relatively few outbreaks linked to whole fresh produce but triggers recalls each year in the United States. There are limited data on the influence of wet versus dry inoculation methods on pathogen growth on whole produce. A cocktail of five L. monocytogenesstrains that included clinical, food, and environmental isolates associated with foodborne outbreaks and recalls was used. Cultures were combined to target a final wet inoculum concentration of 4 to 5 log CFU/mL. The dry inoculum was prepared by mixing wet inoculum with 100 g of sterile sand and drying for 24 h. Produce investigated belonged to major commodity families: Ericaceae (blackberry, raspberry, and blueberry), Rutaceae (lemon and mandarin orange), Rosaceae (sweet cherry), Solanaceae (tomato), Brassaceae (cauliflower and broccoli), and Apiaceae (carrot). Whole intact, inoculated fruit and vegetable commodities were incubated at 2, 12, 22, and 35 ± 2°C. Commodities were sampled for up to 28 days, and the experiment was replicated six times. The average maximum growth increase was obtained by measuring the maximum absolute increase for each replicate within a specific commodity, temperature, and inoculation method. Data for each commodity, replicate, and temperature were used to create primary growth or survival models describing the lag phase and growth or shoulder and decline as a function of time. Use of a liquid inoculum (versus dry inoculum) resulted in a markedly increased L. monocytogenesgrowth rate and growth magnitude on whole produce surfaces. Temperature highly influenced this difference: 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 (e.g., production, harvest, postharvest, transportation, or retail) should be investigated.

Suboptimal food worker health and hygiene has been a common contributing factor in foodborne disease outbreaks for many years. Despite clear U.S. Food and Drug Administration (FDA) Model Food Code recommendations for hand washing and glove use, food worker compliance with hand washing recommendations has remained poor for >20 years. Food workers' compliance with recommended hand washing guidelines is adversely impacted by a number of barriers, including complaints of time pressure, inadequate number and/or location of hand washing sinks and hand washing supplies, lack of food knowledge and training regarding hand washing, the belief that wearing gloves obviates the need for hand washing, insufficient management commitment, and adverse skin effects caused by frequent hand washing. Although many of the issues related to poor hand washing practices in food service facilities are the same as those in health care settings, a new approach to health care hand hygiene was deemed necessary >15 years ago due to persistently low compliance rates among health care personnel. Evidence-based hand hygiene guidelines for health care settings were published by both the Centers for Disease Control and Prevention in 2002 and by the World Health Organization in 2009. Despite similar low hand washing compliance rates among retail food establishment workers, no changes in the Food Code guidelines for hand washing have been made since 2001. In direct contrast to health care settings, where frequent use of alcohol-based hand sanitizers (ABHSs) in lieu of hand washing has improved hand hygiene compliance rates and reduced infections, the Food Code continues to permit the use of ABHSs only after hands have been washed with soap and water. This article provides clear evidence to support modifying the FDA Model Food Code to allow the use of ABHSs as an acceptable alternative to hand washing in situations where heavy soiling is not present. Emphasis on the importance of hand washing when hands are heavily soiled and appropriate use of gloves is still indicated.

Listeria monocytogeneswas associated with more than 60 produce recalls, including tomato, cherry, broccoli, lemon, and lime, between 2017 and 2020. This study describes the effects of temperature, time, and food substrate as factors influencing L. monocytogenesbehavior on whole intact raw fruits and vegetables. Ten intact whole fruit and vegetable commodities were chosen based on data gaps identified in a systematic literature review. Produce investigated belong to major commodity families: Ericaceae (blackberry, raspberry, and blueberry), Rutaceae (lemon and mandarin orange), Roseaceae (sweet cherry), Solanaceae (tomato), Brassaceae (cauliflower and broccoli), and Apiaceae (carrot). A cocktail of five L. monocytogenesstrains that included clinical, food, or environmental isolates linked to foodborne outbreaks was used to inoculate intact whole fruits and vegetables. Samples were incubated at 2, 12, 22, 30, and 35°C with relative humidities matched to typical real-world conditions. Foods were sampled (n= 6) for up to 28 days, depending on temperature. Growth and decline rates were estimated using DMFit, an Excel add-in. Growth rates were compared with ComBase modeling predictions for L. monocytogenes. Almost every experiment showed initial growth, followed by subsequent decline. L. monocytogeneswas able to grow on the whole intact surface of all produce tested, except for carrot. The 10 produce commodities supported growth of L. monocytogenesat 22 and 35°C. Growth and survival at 2 and 12°C varied by produce commodity. The standard deviation of the square root growth and decline rates showed significantly larger variability in both growth and decline rates within replicates as temperature increased. When L. monocytogenesgrowth occurred, it was conservatively modeled by ComBase Predictor, and growth was generally followed by decreases in concentration. This research will assist in understanding the risks of foodborne disease outbreaks and recalls associated with L. monocytogeneson fresh whole produce.

Cucumbers found in retail markets are often waxed to improve visual appeal and retard moisture loss. This waxing may affect bacterial survival, and the waxing process may facilitate cross-contamination between cucumbers. This study assessed the survival of Salmonellaon waxed and unwaxed cucumbers and the potential for Salmonellacross-contamination during the waxing process. Fresh waxed or unwaxed cucumbers were spot inoculated with a cocktail of Salmonella entericastrains. Three different wax coatings (mineral oil, vegetable oil, or petroleum wax) were manually applied to unwaxed cucumbers using polyethylene brushes. Salmonellatransfer from inoculated cucumbers to the brush or to uninoculated cucumbers was quantified. Higher Salmonellaconcentrations were observed on waxed cucumbers during the first 3 days of storage, but the final concentration on unwaxed cucumbers was higher than on waxed cucumbers at the end of storage, regardless of storage temperature. The wax formulation did affect the survival of Salmonellainoculated directly into waxes, with a significant decline in Salmonellapopulations observed in vegetable-based wax coating but with populations unchanged over 7 days at 7 or 21°C in mineral oil–based and petroleum-based waxes. Salmonellacells could transfer from inoculated unwaxed cucumbers to brushes used for waxing and then to uninoculated cucumbers during waxing. A significantly higher log percentage of transfer to brushes was observed when cucumbers were waxed with vegetable oil (0.71 log percent, P= 0.00441) than with mineral oil (0.06 log percent) or petroleum (0.05 log percent). Transfer to uninoculated cucumbers via brushes was also quantified (0.18 to 0.35 log percent transfer). Salmonellaremaining on contaminated cucumbers after waxing could be detected for up to 7 days, and Salmonellasurvived better on cucumbers treated with a petroleum-based wax. These findings should be useful in managing the risk of Salmonellacontamination in cucumbers during postharvest handling.

Outbreaks from improperly cooled foods continue to occur despite clearly described Food Code cooling guidelines. It is difficult for regulators to enforce these guidelines because they are typically in an establishment for less than the 6 h needed to document proper cooling. Prior research proposed using a novel method to estimate cooling rates based on two time-temperature points, but this method has not yet been validated. Time-temperature profiles of 29 different foods were collected in 25 different restaurants during cooling. Cooling curves were divided into two categories: typical (21 foods) and atypical (eight foods) prior to further analysis. Analysis of the typical cooling curves used simple linear regression to calculate cooling rates. The atypical cooling profiles were studied using Monte Carlo simulations of the cooling rate. Almost all linearized typical cooling curves had high (>0.90) R2values. Six foods with typical cooling profiles that did not pass Food Code cooling times were correctly identified by the two-point model as having slow cooling rates. Three foods that did not pass Food Code cooling times were identified by the two-point model as having marginal cooling rates. Ten of 12 foods identified by the two-point model as having acceptable cooling rates met Food Code cooling times. Most (six of eight) foods that were considered to have atypical cooling curves failed to meet the Food Code cooling times. The two-point model was also able to determine whether these foods would fail based on Food Code guidelines depending upon the simulation criteria used. Our data show that food depth has a strong influence on cooling rate. Containers with a food depth ≥7.6 cm (3 in.) were more likely to have cooling rates slower than the U.S. Food and Drug Administration Model Food Code cooling rate. This analysis shows that the two-point method can be a useful screening tool to identify potential cooling rate problems during a routine restaurant inspection visit.

High-moisture slurries used in the production of table spreads may permit growth of Staphylococcus aureusand Bacillus cereusand subsequent production of heat-stable enterotoxins. Compliance with the Food Safety Modernization Act (FSMA), specifically 21 CFR Part 117, subpart B and section 117.80 (c)(2) and (c)(3), requires a hazard analysis to determine whether preventive controls are needed. This study estimates the risk of potential growth of S. aureusand B. cereusin eight different dairy- and non-dairy–based slurries during extended storage and use. Mathematical models were used to screen which slurries might support the growth of S. aureusand B. cereus. Samples were individually inoculated with multiple strains of S. aureusand B. cereusto achieve a target level of 102to 103CFU/g. Inoculated and uninoculated slurry samples were incubated at typical holding temperatures of 35°C (95°F), 46.1°C (115°F), and 54.4°C (130°F). Samples were removed and tested following inoculation (time zero), after 4 and 12 h, and after 1, 2, 3, 4, 5, 6, 7, and 10 days of incubation at the target temperatures. All experiments were repeated in triplicate. Samples were analyzed for S. aureusand B. cereususing Baird-Parker agar and mannitol yolk polymyxin agar, respectively. Neither S. aureusnor B. cereusexceeded (P< 0.05) proposed food safety limits (105CFU/g) at the evaluated experimental conditions. The study highlights the role of multiple hurdles (e.g., pH, potassium sorbate and sodium benzoate, salt, and other ingredients) in assuring microbiological safety of in-process dairy- and non-dairy–based slurries used in the production of table spreads. This study also found that mathematical models representative of product composition, intrinsic parameters, and experimental conditions can help risk managers make informed decisions during product development. Finally, the study findings indicate no significant risk of growth of the target pathogens associated with the dairy- and non-dairy–based aqueous slurries used in the routine manufacturing of table spreads.

Low-water-activity (aw) foods (including those containing fat) are often implicated in outbreaks of Salmonellaspp. The influence of fat content on survival in foods such as peanut butter remains unclear. Certain Salmonellaserovars can survive for long periods in harsh temperatures and low moisture conditions. The objective of this study was to determine the influence of fat content on the survival of Salmonellain low-awfoods and expand an existing secondary inactivation model previously validated for lower-fat foods. Whey protein powder supplemented with peanut oil was equilibrated to five target awvalues (aw< 0.60), inoculated with a dried four-strain cocktail of Salmonella,vacuum sealed, and stored at 22, 37, 50, 60, 70, and 80°C for 48 h, 28 days, or 168 days. Survival data were fitted to Weibull, Biphasic-linear, Double Weibull, and Geeraerd-tail models. The Weibull model was chosen for secondary modeling due to its ability to satisfactorily describe the data over most of the conditions under study. The influence of temperature, fat content, and awon the Weibull model parameters was evaluated using nonlinear least squares regression, and a revised secondary model was developed based on parameter significance. Peanut butter, chia seed powder, toasted oat cereal, and animal crackers within the awrange of the model were used to validate the modified model within its temperature range. Fat content influenced survival in samples held at temperatures ≥50°C, whereas awinfluenced survival at 37 and 70°C. The model predictions demonstrated improved % bias and % discrepancy compared with the previous model. Weibull model predictions were accurate and fail-safe in 38 and 58%, respectively, of the food and environmental conditions under study. Predictions were less reliable for peanut butter held at 80°C. This study provides data and a model that can aid in the development of risk mitigation strategies for low-awfoods containing fat.

Outbreaks and recalls related to nuts and seeds in the United States have increased recently, and 80% of these recalls are due to Salmonella. The U.S. Food and Drug Administration's Food Safety Modernization Act requires food manufacturers to implement risk-based preventive controls based on scientific and technical evidence. Data are limited on the inactivation of Salmonelladuring processing of saltwater brined in-shell sunflower seeds. The goal of this research was to validate the adequacy of roasting in controlling Salmonelladuring the production of sunflower seeds and to assess the resulting risk. Four Salmonellastrains were inoculated onto sunflower seeds and processed to simulate commercial manufacturing. Seeds were tumbled and roasted at 225°F (107.2°C) and 275°F (135°C) for roasting times from 5 to 45 min. Regression models for Salmonellainactivation and water activity change were developed. The inactivation model predicted a 5-log reduction in Salmonellawhen sunflower seeds were roasted at 135°C for 19.2 min, with a corresponding water activity of ∼0.61. Roasted sunflower seeds are typically not saleable at water activities >0.6 due to quality issues. Saleable water activities (0.03 to 0.04) were only achieved when the sunflower seeds were roasted for 45 min at 135°C, which resulted in a >7-log reduction in Salmonella. A quantitative microbial risk assessment based on literature values, expert opinion, and the above-mentioned models was used to predict risk of salmonellosis from sunflower seeds. The quantitative microbial risk assessment model predicted an arithmetic mean probability of illness of 1.45E−07 per 28-g serving based on roasting at 135°C for 20 min and an arithmetic mean probability of illness of 5.46E−10 per serving based on roasting at 135°C for >45 min (i.e., saleable product process parameters). This study demonstrates that sunflower seeds roasted to saleable parameters should not represent a public health risk from potential presence of Salmonella.

Listeria monocytogenesmay be present in produce-associated environments (e.g., fields, packing houses); thus, understanding its growth and survival on intact, whole produce is of critical importance. The goal of this study was to identify and characterize published data on the growth and/or survival of L. monocytogeneson intact fruit and vegetable surfaces. Relevant studies were identified by searching seven electronic databases: AGRICOLA, CAB Abstracts, Center for Produce Safety funded research project final reports, FST Abstracts, Google Scholar, PubMed, and Web of Science. Searches were conducted using the following terms: Listeria monocytogenes,produce, growth, and survival. Search terms were also modified and “exploded” to find all related subheadings. Included studies had to be prospective, describe methodology (e.g., inoculation method), outline experimental parameters, and provide quantitative growth and/or survival data. Studies were not included if methods were unclear or inappropriate, or if produce was cut, processed, or otherwise treated. Of 3,459 identified citations, 88 were reviewed in full and 29 studies met the inclusion criteria. Included studies represented 21 commodities, with the majority of studies focusing on melons, leafy greens, berries, or sprouts. Synthesis of the reviewed studies suggests L. monocytogenesgrowth and survival on intact produce surfaces differ substantially by commodity. Parameters such as temperature and produce surface characteristics had a considerable effect on L. monocytogenesgrowth and survival dynamics. This review provides an inventory of the current data on L. monocytogenesgrowth and/or survival on intact produce surfaces. Identification of which intact produce commodities support L. monocytogenesgrowth and/or survival at various conditions observed along the supply chain will assist the industry in managing L. monocytogenescontamination risk.

Survival of bacteria on surfaces plays an important role in the cross-contamination of food. Temperature, relative humidity (RH), surface type, and inoculum diluent can affect bacterial survival. This study was conducted to examine how temperature, RH, and diluent affect the survival of Enterobacter aerogeneson stainless steel, polyvinyl chloride, and ceramic tile. Although surface type had little effect on survival, temperature had a clear effect. E. aerogenessurvival was highest at 7°C and 15 and 50% RH on all surfaces. Some diluents allowed growth under high RH conditions. Cell populations in distilled water inoculated onto each surface decreased initially compared with populations in 1% phosphate-buffered saline (PBS) and 0.1% peptone broth. At 15 and 50% RH, cell populations in 1% PBS declined more sharply after 120 h than did those 0.1% peptone, but populations in both diluents had similar declines up to 3 weeks. Cell populations in 0.1% peptone had the greatest growth and reached the highest population density (∼8 log CFU/mL). Cell populations in PBS and distilled water increased by ∼2 log CFU/mL. When cells in 0.1% peptone were inoculated onto stainless steel at 100% RH, populations increased to ∼7 log CFU per coupon, whereas cells in 1% PBS increased to ∼5 log CFU per coupon followed by a decline over 3 weeks. DMFit and GInaFiT software modeled inactivation on surfaces at all conditions other than 100% RH at 21°C. These findings have important implications for experiments in which microorganisms are inoculated onto foods or food contact surfaces because the growth observed may be affected more by the inoculum diluent at high or uncontrolled RH than by the type of inoculated surface.

Peanut products were the target of the largest food recall in United States history from 2008 to 2009, with more than 3,200 products implicated, economic losses estimated at $1 billion, and more than 700 reported illnesses and 9 deaths. Predictive modeling tools such as quantitative microbial risk assessment can be used to aid processors in making risk management decisions that may reduce the chances of foodborne illness, but published risk assessment for peanuts is not currently available. A quantitative microbial risk assessment was performed to quantify salmonellosis risk from consumption of peanuts in the United States. Prevalence and concentration data for Salmonellaon raw, shelled peanuts were used in combination with probability distributions of simulated log reductions achieved during production steps before consumption. Data for time-temperature combinations used in each step were obtained from published literature, industry surveys, or expert opinion, and survival data were obtained from the literature. A beta-Poisson dose-response model was used to predict probability of illness from ingestion of Salmonellacells. The model predicted 14.2 (arithmetic mean) or 0.0123 (geometric mean) illnesses per year. Sensitivity analysis showed that thermal inactivation log reductions applied had the biggest impact on predicted salmonellosis risk, followed by consumer storage time, Salmonellastarting concentration, Salmonellastarting prevalence, and number of originally contaminated 25-g servings per originally positive 375-g sample. Scenario analysis showed that increasing log reduction variability increased mean salmonellosis risk. Removing the effect of storage on Salmonellasurvival increased the arithmetic and geometric means to 153 and 0.598 illnesses per year, respectively. This study indicated that the risk of salmonellosis from consumption of peanuts can be lowered by reducing field contamination, control of storage steps, and monitoring of appropriate critical limits in peanut roasting.

Fifteen outbreak-linked Salmonella entericastrains in chicken meat were evaluated under simulated human gastrointestinal conditions for their resistance and susceptibility to 11 antibiotics from seven antibiotic classes. The MIC of each antibiotic was determined by microdilution in broth before and after the exposure of each strain to a continuous system simulating the conditions in the human mouth, esophagus-stomach, duodenum, and ileum. Strains were inoculated onto chicken breast (9 g; inoculated at 5 log CFU/g) prior to exposure. Data were interpreted according Clinical and Laboratory Standards Institute breakpoints. After the in vitro digestion, 12 Salmonellastrains with reduced susceptibility to ciprofloxacin (CIP) changed to CIP resistant. The ceftriaxone (CTX)–intermediate SalmonellaNewport strain changed to CTX resistant. The ampicillin (AMP)–susceptible SalmonellaHeidelberg strain changed to AMP resistant, and the sulfamethoxazole-trimethoprim (SXT)–susceptible strains of Salmonellaserovars Typhimurium, Agona, Newport, Albany, and Corvallis changed to SXT resistant. The SalmonellaHeidelberg, SalmonellaNewport, SalmonellaAlbany, and SalmonellaCorvallis strains had the highest frequency of changes in antibiotic susceptibility with new resistant phenotypes to AMP and CIP, CTX and SXT, CIP and SXT, and CIP and SXT, respectively. Conditions imposed by a simulated gastrointestinal environment changed the susceptibility of S. entericastrains to clinically relevant antibiotics and should be considered in the selection of therapies for human salmonellosis.

This study evaluated the microbiological and physicochemical characteristics in different commercial brands of a Brazilian minimally ripened (coalho) cheese during 60 days of storage under refrigeration. Combinations of maximum and minimum values of water activity and pH determined in cheese samples at refrigeration temperature (7°C) were used in a bacterial growth prediction analysis. Maximum growth rate (Grmax) was estimated for different pathogenic and/or spoilage bacteria using the ComBase Predictor. Results of microbiological characterization analyses showed persistent high counts for all monitored microbial groups (Lactobacillusspp., Lactococcusspp., Enterococcusspp., Staphylococcusspp., Enterobacteriaceae,proteolytic and lipolytic microorganisms, and fungi) in cheese samples; no dominant microbial group was observed over time. Values of pH (6.03±0.16 to 7.28 ± 0.55), acidity (0.15% ± 0.09% to 0.66% ± 0.26%), sodium chloride (1.05% ± 0.19% to 1.97% ± 0.75%), and water activity (0.948±0.020 to 0.974 ± 0.012) did not vary in cheese samples during storage. Estimated Grmax values for the tested bacteria were in the range of 0.004 to 0.044 log CFU/h. Highest Grmax values (0.005 to 0.044 log CFU/h) were predicted for the psychrotrophic Aeromonas hydrophila, Listeria monocytogenes, Pseudomonasspp., and Yersinia enterocolitica. Grmax values predicted for Escherichia coli, Salmonellaspp., and Staphylococcus aureuswere in the range of 0.004 to 0.016 log CFU/h. These results indicate unsatisfactory microbiological characteristics of commercially available coalho cheese. Physicochemical characteristics of commercial coalho cheese stored under refrigeration allow bacterial growth to occur, indicating higher risk for fast growth of contaminant bacteria in this product.

This work investigates the efficacy of plasma-activated water (PAW) and plasma-activated acidified buffer (PAAB) on Enterobacter aerogenesin aqueous system and fruit systems. Reactive oxygen and nitrogen species in PAW have been suggested to provide antimicrobial and acidifying effects, causing the pH of treated water to drop. To isolate the effect of pH in microbial inactivation and to study the interactive effects of pH and reactive species on microbial inactivation, a citrate-phosphate buffer (pH 3.1) and PAAB (citrate-phosphate) were studied. A 1.92±0.70 log CFU/mL reduction in E. aerogeneswas observed in PAW, while no reduction was achieved in the buffer, suggesting that the inactivation was due to the reactive species in PAW and not the acidic pH. PAAB achieved a 5.11±0.63 log CFU/mL reduction, suggesting an interactive effect of reactive species and low pH. Electrical conductivity and oxidation-reduction potential measurements suggest potential mechanisms for the greater antimicrobial efficacy of PAAB over PAW. Four surfaces of increasing roughness (glass slides, grape tomatoes, limes, and spiny gourds) were spot inoculated and washed with distilled water, PAW, buffer, and PAAB for 3 min. The smoothest surface (glass) showed the highest reduction (6.32±0.43 log CFU per surface), while the roughest surface (spiny gourd) showed a significantly lower reduction (2.52±0.46 log CFU per surface) when treated with PAAB. For treatment with PAW, no significant differences were observed between glass slides, limes, and spiny gourds. With PAW treatment, significantly lower reduction was observed on spiny gourds (1.70±0.21 log CFU per surface) than on grape tomatoes (4.65±1.34 log CFU per surface). PAW and PAAB both showed potential for their use in fresh produce sanitation.

Concern has been raised regarding the public health risks from refillable bulk-soap dispensers because they provide an environment for potentially pathogenic bacteria to grow. This study surveyed the microbial quality of open refillable bulk soap in four different food establishment types in three states. Two hundred ninety-six samples of bulk soap were collected from food service establishments in Arizona, New Jersey, and Ohio. Samples were tested for total heterotrophic viable bacteria, Pseudomonas,coliforms and Escherichia coli,and Salmonella. Bacteria were screened for antibiotic resistance. The pH, solids content, and water activity of all soap samples were measured. Samples were assayed for the presence of the common antibacterial agents triclosan and parachlorometaxylenol. More than 85% of the soap samples tested contained no detectable microorganisms, but when a sample contained any detectable microorganisms, it was most likely contaminated at a very high level (∼7 log CFU/mL). Microorganisms detected in contaminated soap included Klebsiella oxytoca, Serratia liquefaciens, Shigella sonnei, Enterobacter gergoviae, Serratia odorifera,and Enterobacter cloacae. Twenty-three samples contained antibiotic-resistant organisms, some of which were resistant to two or more antibiotics. Every sample containing less than 4% solids had some detectable level of bacteria, whereas no samples with greater than 14% solids had detectable bacteria. This finding suggests the use of dilution and/or low-cost formulations as a cause of bacterial growth. There was a statistically significant difference (P= 0.0035) between the fraction of bacteria-positive samples with no detected antimicrobial agent (17%) and those containing an antimicrobial agent (7%). Fast food operations and grocery stores were more likely to have detectable bacteria in bulk-soap samples compared with convenience stores (P< 0.05). Our findings underscore the risk to public health from use of refillable bulk-soap dispensers in food service establishments.

This study investigates the efficacy of cold atmospheric pressure plasma (CAPP) on microbial inactivation as influenced by surface roughness of two types of surfaces: sandpaper and fresh fruit peel. Different grits of closed-coat sandpaper were selected, with their roughness (Pq) values ranging from 6 to 16 μm. Apple, orange, and cantaloupe peels were selected for roughness values that were similar to the sandpapers. The sandpapers and the fruit peel surfaces were spot inoculated with Enterobacter aerogenes(109CFU/63.64 cm2) and exposed to CAPP for 492 s. Similar microbial enumeration techniques were used for both systems to quantify the microbial inactivation. The smoothest sandpaper showed a 0.52-log higher inactivation of E. aerogenes(2.08 log CFU/63.64 cm2sandpaper surface inactivation) than did the roughest sandpaper (1.56 log CFU/63.64 cm2sandpaper surface inactivation), and the difference was statistically significant (P< 0.05). The smoothest fresh fruit peel surface (apple) showed a 1.25-log higher inactivation of the microorganism (1.86 log CFU/63.64 cm2fruit peel surface inactivation) than did the roughest fresh fruit peel surface (cantaloupe; 0.61 log CFU/63.64 cm2fruit peel surface inactivation), and the difference was statistically significant (P< 0.05). As the surface roughness increased, microbial inactivation efficacy of CAPP decreased for both systems. The results from sandpaper show that, in a scenario in which the surface roughness was the only parameter of difference, the microbial inactivation efficacy of CAPP decreased with increasing surface roughness. The results from fruit surfaces show high variability and were not directly predictable from the sandpaper data. This suggests that the microbial inactivation efficacy of CAPP in real-world food systems, such as on fresh fruit peels, is affected by factors in addition to surface roughness.

Coalho is a semihard medium- to high-moisture cheese produced in various states in the northeastern region of Brazil. This study was conducted to predict the growth kinetics (maximum growth rate, Grmax) of Escherichia coli, Listeria monocytogenes, Salmonella,and Staphylococcus aureususing the ComBase predictor with various combinations of temperature, pH, and water activity (aw) in commercial Coalho cheese samples. The growth of two antibiotic-resistant derivative strains of L. monocytogenes(parental strains ATCC 19115 and ATCC 7644) and S. aureus(parental strains ATCC 13565 and ATCC 19095) was measured in commercial Coalho cheese samples during 14 days of storage as a function of the initial contamination level (3 and 5 log CFU/g) and storage temperature (7.5 and 12°C). The highest Grmax values predicted by ComBase under the various conditions of temperature, pH, and awwere for L. monocytogenes(0.006 to 0.065 log CFU/g/h) and S. aureus(0.003 to 0.048 log CFU/g/h). The Grmax values predicted by ComBase for E. coliand Salmonellawere 0.007 to 0.026 and 0.008 to 0.041 log CFU/g/h, respectively. An experimental challenge in Coalho cheese revealed that the populations of all tested antibiotic-resistant derivative strains of L. monocytogenesand S. aureusincreased (>0.5 log CFU/g) by day 14 of storage at 7.5 or 12°C. L. monocytogenesand S. aureushad higher Grmax values in cheese samples stored at 12°C than those stored at 7.5°C. The ComBase growth predictions under the temperature, pH, and awconditions in commercial Coalho cheese samples were generally fail-safe for predicting the growth of L. monocytogenesand S. aureusin the actual product. These results indicate that Coalho cheese has pH and awcharacteristics that allow the growth of E. coli, L. monocytogenes, Salmonella,and S. aureus. These cheeses are typically stored at temperatures that do not prevent the growth of these bacteria.

The literature on hand washing, while extensive, often contains conflicting data, and key variables are only superficially studied or not studied at all. Some hand washing recommendations are made without scientific support, and agreement between recommendations is limited. The influence of key variables such as soap volume, lather time, water temperature, and product formulation on hand washing efficacy was investigated in the present study. Baseline conditions were 1 mL of a bland (nonantimicrobial) soap, a 5-s lather time, and 38°C (100°F) water temperature. A nonpathogenic strain of Escherichia coli(ATCC 11229) was the challenge microorganism. Twenty volunteers (10 men and 10 women) participated in the study, and each test condition had 20 replicates. An antimicrobial soap formulation (1% chloroxylenol) was not significantly more effective than the bland soap for removing E. coliunder a variety of test conditions. Overall, the mean reduction was 1.94 log CFU (range, 1.83 to 2.10 log CFU) with the antimicrobial soap and 2.22 log CFU (range, 1.91 to 2.54 log CFU) with the bland soap. Overall, lather time significantly influenced efficacy in one scenario, in which a 0.5-log greater reduction was observed after 20 s with bland soap compared with the baseline wash (P= 0.020). Water temperature as high as 38°C (100°F) and as low as 15°C (60°F) did not have a significant effect on the reduction of bacteria during hand washing; however, the energy usage differed between these temperatures. No significant differences were observed in mean log reductions experienced by men and women (both 2.08 log CFU; P= 0.988). A large part of the variability in the data was associated with the behaviors of the volunteers. Understanding what behaviors and human factors most influence hand washing may help researchers find techniques to optimize the effectiveness of hand washing.

Although studies have quantified bacterial transfer between hands and various materials, cross-contamination between the surface of fresh citrus fruit and the edible portions during hand peeling has not been reported. This study quantifies transfer of Salmonellato the edible portion of citrus fruit from a contaminated peel during hand peeling. Citrus fruits used for this study were Citrus sinensis(sweet orange) cultivars ‘Valencia' and ‘Navel’, Citrus unshiu(Satsuma mandarins), Citrus reticulata× Citrus paradisi(‘Minneola' tangelo or ‘Honeybell'), and C. paradisi(grapefruit) cultivar ‘Marsh’. An avirulent Salmonella TyphimuriumLT2 (ATCC 700720) resistant to rifampin was used for all experiments. The inoculum containing approximately 9 log CFU/mL (50 μL) was spot inoculated onto the equator, stem, or styler of each fruit and allowed to dry for 24 h. Six volunteers put on single-use latex gloves and peeled inoculated fruit. Peel, edible fruit portion, and gloves were collected and enumerated separately. Three replicates of the study were performed in which each volunteer peeled two inoculated fruit of each variety (n= 36 fruit per variety). Cross-contamination from contaminated surface of citrus fruits to edible portion or gloved hands during peeling was affected by inoculation sites. Average Salmonellatransfer to the edible portion ranged from 0.16% (Valencia inoculated at the equator) to 5.41% (navel inoculated at the stem). Average Salmonellatransfer to gloved hands ranged from 0.41% (grapefruit inoculated at the stem) to 8.97% (navel inoculated at the stem). Most Salmonellaremained on the peel of citrus fruits. The average level of Salmonellaremaining on the peel ranged from 5.37% (Minneola inoculated at the equator) to 66.3% (Satsuma inoculated at the styler). When grapefruit was inoculated, the Salmonellathat remained on the peel showed a bimodal pattern in which some individuals left almost all Salmonellaon the peel, while others left substantially less.

Leafy green vegetables, including lettuce, are recognized as potential vehicles for foodborne pathogens such as Escherichia coliO157:H7. Fresh-cut lettuce is potentially at high risk of causing foodborne illnesses, as it is generally consumed without cooking. Quantitative microbial risk assessments (QMRAs) are gaining more attention as an effective tool to assess and control potential risks associated with foodborne pathogens. This study developed a QMRA model for E. coliO157:H7 in fresh-cut lettuce and evaluated the effects of different potential intervention strategies on the reduction of public health risks. The fresh-cut lettuce production and supply chain was modeled from field production, with both irrigation water and soil as initial contamination sources, to consumption at home. The baseline model (with no interventions) predicted a mean probability of 1 illness per 10 million servings and a mean of 2,160 illness cases per year in the United States. All intervention strategies evaluated (chlorine, ultrasound and organic acid, irradiation, bacteriophage, and consumer washing) significantly reduced the estimated mean number of illness cases when compared with the baseline model prediction (from 11.4- to 17.9-fold reduction). Sensitivity analyses indicated that retail and home storage temperature were the most important factors affecting the predicted number of illness cases. The developed QMRA model provided a framework for estimating risk associated with consumption of E. coliO157:H7–contaminated fresh-cut lettuce and can guide the evaluation and development of intervention strategies aimed at reducing such risk.

This study quantifies the cross-contamination rates between fresh-cut produce and hands using a nalidixic acid–resistant nonpathogenic Enterobacter aerogenesand cocktails of rifampin-resistant Salmonellaor Escherichia coliO157:H7 strains. Volunteers performed the E. aerogenesexperiments (n= 20), and one of the authors performed the Salmonellaand E. coliO157:H7 experiments multiple times (n=15 and n=10, respectively). Each participant handled 25 g of fresh-cut carrots, celery, or cantaloupe in two different scenarios. In the first scenario, gloved hands were inoculated with 6 log CFU per hand of the bacteria, and in the second scenario, five 25-g pieces of fresh produce were inoculated to a concentration of 6 log CFU/25 g. The glove juice method was used to quantify the bacterial concentration on the gloved hands. About 30% of E. aerogeneson gloved hands was transferred to the carrots and celery, and 18% of E. aerogeneson gloved hands was transferred to the cantaloupe. When carrots or cantaloupe was inoculated with E. aerogenes, 1% was transferred to gloved hands; from inoculated celery, about 0.3% of E. aerogeneswas transferred to gloved hands. There was not a significant difference between E. aerogenesand Salmonellacross-contamination rates (P> 0.05). When gloved hands were contaminated with E. coliO157:H7, about 30% was transferred to carrots, about 10% to celery, and about 3% to cantaloupe. When carrots and celery were inoculated with E. coliO157:H7, about 1% was transferred to gloved hands, but from inoculated cantaloupe only about 0.3% was transferred. Direction of transfer (to versus from produce), difference in type of produce, and differences among the bacterial species all had significant effects on the transfer rate. Understanding transfer rates to and from fresh-cut produce will allow for better risk assessment and management of microbial food safety risk related to fresh-cut produce.

•Three berries heated for 60 s at 100% power yielded a 3.8 ± 0.2 log reduction in MS2.•Surveyed berry package microwaving directions are very diverse.•Virus inactivation could be modeled using a temperature path-dependent D-value.•The model fit the data well, with a RMSE of 0.5 PFU/g for a 6-log reduction.•This is a first step to model microwave virus inactivation on frozen strawberries.

This research was undertaken to determine the effectiveness of an alcohol-based hand sanitizer on hands contaminated with a nonpathogen surrogate for Escherichia coliO157:H7, where the source of the contamination was frozen hamburger patties. A nonpathogenic nalidixic acid–resistant food-grade strain of Enterobacter aerogeneswas used to inoculate frozen hamburger patties composed of 76% lean beef and 24% fat. Thirty-two individuals participated to produce the data used in this study. Each participant handled nine patties at least three times, a sample for microbiological analysis was collected from the surface of one hand, the participant sanitized both hands, and a sample was collected from the other hand. Burger handling created perceptible and visible food debris on the hands of most participants. Computer simulations also were used to perform a variety of risk calculations. The average reduction in bacteria from the use of sanitizer on hands contaminated by frozen burgers containing E. aerogeneswas 2.6±0.7 log CFU per hand. An experiment designed to simultaneously test the effect of sanitizer on E. aerogenesand E. coliO157:H7 also revealed no significant difference in sanitizer effectiveness against the two organisms. The results of the real-world risk estimation calculations (using the actual prevalence and concentration of E. coliO157:H7 in ground beef) predict that once in 1 million trials, a single pathogen cell will be transferred to a single lettuce piece. The effectiveness of this sanitizer intervention was similar to that for hand washing and glove use previously reported. The person-to-person microbial reduction variability from sanitizer use is similar to published data for glove use and was less variable than published data on hand washing effectiveness.

A recent study by the Centers for Disease Control and Prevention reported that between 1998 and 2008, leafy greens outbreaks accounted for 22.3% of foodborne outbreaks in the United States. Several studies on the growth of bacteria at different temperatures have been conducted; however, there is a need for the prediction of bacterial growth when leafy greens are transported without temperature control. Food products, when taken out of refrigeration, undergo a temperature change, with the rate of temperature change being proportional to the difference in the temperature of food and its surroundings. The objective of this study was to estimate the growth of Escherichia coliO157:H7, Salmonella enterica, and L. monocytogenesin leafy greens during transportation from retail to home at ambient temperatures ranging from 10 to 40°C for up to 10 h. Experiments were conducted to monitor the temperature increase in fresh spinach taken from refrigeration temperature to ambient temperature. The growth of pathogens was predicted using these changing temperature profiles with the three-phase linear model as a primary model and the square root model as the secondary model. The levels of E. coliO157:H7, S. enterica, and L. monocytogenesincreased by 3.12, 2.43, and 3.42 log CFU at 40°C for the 10-h period, respectively, when no lag phase was assumed. If leafy greens are not kept out of refrigeration for more than 3 h, when the air temperature is 40°C or more, pathogen growth should be less than 1 log CFU. These results would assist in developing recommendations for food transportation without refrigeration.

•Washing removed more (p < 0.05) curli− cells from leaf surfaces vs curli+ cells.•Washing also removed more (p < 0.05) curli− cells from leaf edges.•Curli+ cells always showed more (p < 0.05) transfer to noninoculated leaves.•When inoculated leaves were washed, most contamination ended up in the wash water.•Less than 1% of the contamination on inoculated leaves was transferred to other leaves.

•Health and hygiene was ranked of highest importance with industry community members.•PAC respondents ranked adjacent land use of highest importance.•Grower and technical assistance groups similarly ranked priorities.•Priority rankings differed by operation size.

•Pizza is more frequently out of temperature control than many other foods.•pH and water activity of pizza indicate time temperature control for safety needed.•Total plate counts on pizza do not correlate with sample pick up temperature.•Predictive model shows that Staphylococcus aureusposes the greatest risk.•Risk manifests for pizza held at 30 °C or less for more than 8 hours.

•Contact time and sanitizer type influenced STEC and E. coliTVS 353 reductions.•STEC panel was more sensitive to chlorine and peracetic acid than E. coliTVS 353.•All Cl treatments achieved ≥3 log10CFU/100 mL reduction in STEC and E. coliTVS 353.•E. coliTVS 353 is a good surrogate candidate for in-field experiment validations.•Water quality management is important to maintain residual sanitizer concentrations.

•Salmonellareductions were evaluated in agriculture water treated with sanitizers.•Sanitizer type and contact time were strongly associated with Salmonellareductions.•Outbreak strains were more treatment-resistant than environmental strains.•Varying volumes of sanitizers were needed to reach target ppm in the water sources.•Effective treatment requires accounting for water quality to ensure valid dosing

This study assessed the inhibitory effects of the essential oil from Origanum vulgareL. (OVEO) on Staphylococcus aureus, Listeria monocytogenes, and a mesophilic starter coculture composed of lactic acid bacteria (Lactococcus lactissubsp. lactisand L. lactissubsp. cremoris) in Brazilian coalhocheese systems. The MIC of OVEO was 2.5 μl/ml against both S. aureusand L. monocytogenesand 0.6 μl/ml against the tested starter coculture. In cheese broth containing OVEO at 0.6 μl/ml, no decrease in viable cell counts (VCC) of both pathogenic bacteria was observed, whereas the initial VCC of the starter coculture decreased approximately 1.0 log CFU/ml after 24 h of exposure at 10°C. OVEO at 1.25 and 2.5 μl/ml caused reductions of up to 2.0 and 2.5 log CFU/ml in S. aureusand L. monocytogenes,respectively, after 24 h of exposure in cheese broth. At these same concentrations, OVEO caused a greater decrease of initial VCC of the starter coculture following 4 h of exposure. Higher concentrations of OVEO were required to decrease the VCC of all target bacteria in semisolid coalho cheese slurry compared with cheese broth. The VCC of Lactococcusspp. in coalho cheese slurry containing OVEO were always lower than those of pathogenic bacteria under the same conditions. These results suggest that the concentrations of OVEO used to control pathogenic bacteria in semihard cheese should be carefully evaluated because of its inhibitory effects on the growth of starter lactic acid cultures used during the production of the product.

Heat-resistant spores of Clostridium perfringensmay germinate and multiply in cooked meat and poultry products when the rate and extent of cooling does not occur in a timely manner. Therefore, six cooling models (PMP 7.0 broth model; PMIP uncured beef, chicken, and pork models; Smith-Schaffner version 3; and UK IFR ComBase Perfringens Predictor) were evaluated for relative performance in predicting growth of C. perfringensunder dynamic temperature conditions encountered during cooling of cooked, uncured meat and poultry products. The predicted growth responses from the models were extensively compared with those observed in food. Data from 188 time-temperature cooling profiles (176 for single-rate exponential cooling and 12 for dual-rate exponential cooling) were collected from 17 independent sources (16 peer-reviewed publications and one report) for model evaluation. Data were obtained for a variety of cooked products, including meat and poultry slurries, ground meat and poultry products with and without added ingredients (e.g., potato starch, sodium triphosphate, and potassium tetrapyrophosphate), and processed products such as ham and roast beef. Performance of the models was evaluated using three sets of criteria, and accuracy was defined within a 1-to 2-log range. The percentages of accurate, fail-safe, or fail-dangerous predictions for each cooling model differed depending on which criterion was used to evaluate the data set. Nevertheless, the combined percentages of accurate and fail-safe predictions based on the three performance criteria were 34.66 to 42.61% for the PMP 7.0 beef broth model, 100% for the PMIP cooling models for uncured beef, uncured pork and uncured chicken, 80.11 to 93.18% for the Smith-Schaffner cooling model, and 74.43 to 85.23% for the UK IFR ComBase Perfringens Predictor model during single-rate exponential chilling. Except for the PMP 7.0 broth model, the other five cooling models (PMIP, Smith-Schaffner, and UK IFR ComBase) are useful and reliable tools that food processors and regulatory agencies can use to evaluate the safety of cooked or heat-treated uncured meat and poultry products exposed to cooling deviations or to develop customized cooling schedules.

Data collected by the Centers for Disease Control and Prevention (CDC) show that improper cooling practices contributed to more than 500 foodborne illness outbreaks associated with restaurants or delis in the United States between 1998 and 2008. CDC’s Environmental Health Specialists Network (EHS-Net) personnel collected data in approximately 50 randomly selected restaurants in nine EHS-Net sites in 2009 to 2010 and measured the temperatures of cooling food at the beginning and the end of the observation period. Those beginning and ending points were used to estimate cooling rates. The most common cooling method was refrigeration, used in 48% of cooling steps. Other cooling methods included ice baths (19%), room-temperature cooling (17%), ice-wand cooling (7%), and adding ice or frozen food to the cooling food as an ingredient (2%). Sixty-five percent of cooling observations had an estimated cooling rate that was compliant with the 2009 Food and Drug Administration Food Code guideline (cooling to 41°F [5°C] in 6 h). Large cuts of meat and stews had the slowest overall estimated cooling rate, approximately equal to that specified in the Food Code guideline. Pasta and noodles were the fastest cooling foods, with a cooling time of just over 2 h. Foods not being actively monitored by food workers were more than twice as likely to cool more slowly than recommended in the Food Code guideline. Food stored at a depth greater than 7.6 cm (3 in.) was twice as likely to cool more slowly than specified in the Food Code guideline. Unventilated cooling foods were almost twice as likely to cool more slowly than specified in the Food Code guideline. Our data suggest that several best cooling practices can contribute to a proper cooling process. Inspectors unable to assess the full cooling process should consider assessing specific cooling practices as an alternative. Future research could validate our estimation method and study the effect of specific practices on the full cooling process.

Hand washing is recognized as a crucial step in preventing foodborne disease transmission by mitigating cross-contamination among hands, surfaces, and foods. This research was undertaken to establish the importance of several keys factors (soap, soil, time, and drying method) in reducing microorganisms during hand washing. A nonpathogenic nalidixic acid–resistant Enterobacter aerogenessurrogate for Salmonellawas used to assess the efficacy of using soap or no soap for 5 or 20 s on hands with or without ground beef debris and drying with paper towel or air. Each experiment consisted of 20 replicates, each from a different individual with ~ 6 log CFU/ml E. aerogeneson their hands. A reduction of 1.0 ± 0.4 and 1.7 ± 0.8 log CFU of E. aerogeneswas observed for a 5-s wash with no soap and a 20-s wash with soap, respectively. When there was no debris on the hands, there was no significant difference between washing with and without soap for 20 s (P <0.05). Likewise, there was no significant difference in the reductions achieved when washing without soap, whether or not debris was on the hands (P> 0.05). A significantly greater reduction (P< 0.05) in E. aerogenes(0.5 log CFU greater reduction) was observed with soap when there was ground beef debris on the hands. The greatest difference (1.1 log CFU greater average reduction) in effectiveness occurred when ground beef debris was on the hands and a 20-s wash with water was compared with a 20-s wash with soap. Significantly greater (P< 0.05) reductions were observed with paper towel drying compared with air (0.5 log CFU greater reductions). Used paper towels may contain high bacterial levels (>4.0 log CFU per towel) when hands are highly contaminated. Our results support future quantitative microbial risk assessments needed to effectively manage risks of foodborne illness in which food workers’ hands are a primary cause.

Whole and diced yellow onions (Allium cepa)were inoculated with five-strain cocktails of rifampin-resistant Escherichia coliO157:H7 or Salmonellaand stored under conditions to simulate food service or consumer handling. The inoculum was grown in broth (for both whole and diced onion experiments) or on agar plates (for whole onion experiments). Marked circles (3.3 cm in diameter) on the outer papery skin of whole onions were spot inoculated (10 µl in 10 drops) at 7 log CFU per circle, and onions were stored at 4°C, 30 to 50% relative humidity, or at ambient conditions (23°C, 30 to 50% relative humidity). Diced onions were inoculated at 3 log CFU/g and then stored in open or closed containers at 4°C or ambient conditions. Previously inoculated and ambient-stored diced onions were also mixed 1:9 (wt/wt) with refrigerated uninoculated freshly diced onions and stored in closed containers at ambient conditions. Inoculated pathogens were recovered in 0.1% peptone and plated onto selective and nonselective media supplemented with 50 μg/ml rifampin. Both E. coliO157:H7 and Salmonellapopulations declined more rapidly on onion skins when the inoculum was prepared in broth rather than on agar. Agar-prepared E. coliO157:H7 and Salmonelladeclined by 0.4 and 0.3 log CFU per sample per day, respectively, at ambient conditions; at 4°C the rates of reduction were 0.08 and 0.06 log CFU per sample per day for E. coliO157:H7 and Salmonella,respectively. Populations of E. coliO157:H7 and Salmonelladid not change over 6 days of storage at 4°C in diced onions. Lag times of 6 to 9 h were observed with freshly inoculated onion at ambient conditions; no lag was observed when previously inoculated and uninoculated onions were mixed. Growth rates at ambient conditions were 0.2 to 0.3 log CFU/g/h for E. coliO157:H7 and Salmonellain freshly inoculated onion and 0.2 log CFU/g/h in mixed product. Diced onions support pathogen growth and should be kept refrigerated.

Peanut butter has been associated with several large foodborne salmonellosis outbreaks. This research investigates the potential of high hydrostatic pressure processing (HPP) for inactivation of Salmonellain peanut butter of modified composition, both by modifying its water activity as well by the addition of various amounts of nisin. A cocktail of six Salmonellastrains associated with peanut butter and nut-related outbreaks was used for all experiments. Different volumes of sterile distilled water were added to peanut butter to increase water activity, and different volumes of peanut oil were added to decrease water activity. Inactivation in 12% fat, light roast, partially defatted peanut flour, and peanut oil was also quantified. Nisaplin was incorporated into peanut butter at four concentrations corresponding to 2.5, 5.0, 12.5, and 25.0 ppm of pure nisin. All samples were subjected to 600 MPa for 18 min. A steady and statistically significant increase in log reduction was seen as added moisture was increased from 50 to 90%. The color of all peanut butter samples containing added moisture contents darkened after high pressure processing. The addition of peanut oil to further lower the water activity of peanut butter further reduced the effectiveness of HPP. Just over a 1-log reduction was obtained in peanut flour, while inactivation to below detection limits (2 log CFU/g) was observed in peanut oil. Nisin alone without HPP had no effect. Recovery of Salmonellaafter a combined nisin and HPP treatment did show increased log reduction with longer storage times. The maximum log reduction of Salmonellaachieved was 1.7 log CFU/g, which was comparable to that achieved by noncycling pressure treatment alone. High pressure processing alone or with other formulation modification, including added nisin, is not a suitable technology to manage the microbiological safety of Salmonella-contaminated peanut butter.

Factors such as temperature, water activity (aw), substrate, culture media, serotype, and strain influence the survival of Salmonellain low-awfoods. Predictive models for Salmonellasurvival in low-awfoods at temperatures ranging from 21 to 80°C and water activities below 0.6 were previously developed. Literature data on survival of Salmonellain low-awfoods were analyzed in the present study to validate these predictive models and to determine global influencing factors. The results showed the Weibull model provided suitable fits to the data in 75% of the curves as compared with the log-linear model. The secondary models predicting the time required for log-decimal reduction (log δ) and shape factor (log β) values were useful in predicting the survival of Salmonellain low-awfoods. Statistical analysis indicated overall fail-safe secondary models, with 88% of the residuals in the acceptable and safe zones (< 0.5 log CFU) and a 59% correlation coefficient (R2= 0.35). A high variability in log δ-values and log β-values was observed, emphasizing the importance of experimental design. Factors of significant influence on the times required for first log-decimal reduction included temperature, aw, product, and serotype. Log β-values were significantly influenced by serotype, the type of inoculum (wet or dry), and whether the recovery media was selective or not. The results of this analysis provide a general overview of survival kinetics of Salmonellain low-awfoods and its influencing factors.

Temperature is a primary factor in controlling the growth of microorganisms in food. The current U.S. Food and Drug Administration Model Food Code guidelines state that food can be kept out of temperature control for up to 4 h without qualifiers, or up to 6 h, if the food product starts at an initial 41°F (5°C) temperature and does not exceed 70°F (21°C) at 6 h. This project validates existing ComBase computer models for Salmonellagrowth under changing temperature conditions modeling scenarios using raw ground beef as a model system. A cocktail of Salmonellaserovars isolated from different meat products (SalmonellaCopenhagen, SalmonellaMontevideo, SalmonellaTyphimurium, SalmonellaSaintpaul, and SalmonellaHeidelberg) was made rifampin resistant and used for all experiments. Inoculated samples were held in a programmable water bath at 4.4°C (40°F) and subjected to linear temperature changes to different final temperatures over various lengths of time and then returned to 4.4°C (40°F). Maximum temperatures reached were 15.6, 26.7, or 37.8°C (60, 80, or 100°F), and the temperature increases took place over 4, 6, and 8 h, with varying cooling times. Our experiments show that when maximum temperatures were lower (15.6 or 26.7°C), there was generally good agreement between the ComBase models and experiments: when temperature increases of 15.6 or 26.7°C occurred over 8 h, experimental data were within 0.13 log CFU of the model predictions. When maximum temperatures were 37°C, predictive models were fail-safe. Overall bias of the models was 1.11. and accuracy was 2.11. Our experiments show the U.S. Food and Drug Administration Model Food Code guidelines for holding food out of temperature control are quite conservative. Our research also shows that the ComBase models for Salmonellagrowth are accurate or fail-safe for dynamic temperature conditions as might be observed due to power loss from natural disasters or during transport out of temperature control.

There are conflicting reports on whether antibacterial hand hygiene products are more effective than nonantibacterial products in reducing bacteria on hands and preventing disease. This research used new laboratory data, together with simulation techniques, to compare the ability of nonantibacterial and antibacterial products to reduce shigellosis risk. One hundred sixty-three subjects were used to compare five different hand treatments: two nonantibacterial products and three antibacterial products, i.e., 0.46% triclosan, 4% chlorhexidine gluconate, or 62% ethyl alcohol. Hands were inoculated with 5.5 to 6 log CFU Shigella; the simulated food handlers then washed their hands with one of the five products before handling melon balls. Each simulation scenario represented an event in which 100 people would be exposed to Shigellafrom melon balls that had been handled by food workers with Shigellaon their hands. Analysis of experimental data showed that the two nonantibacterial treatments produced about a 2-log reduction on hands. The three antibacterial treatments showed log reductions greater than 3 but less than 4 on hands. All three antibacterial treatments resulted in statistically significantly lower concentration on the melon balls relative to the nonantibacterial treatments. A simulation that assumed 1 million Shigellabacteria on the hands and the use of a nonantibacterial treatment predicted that 50 to 60 cases of shigellosis would result (of 100 exposed). Each of the antibacterial treatments was predicted to result in an appreciable number of simulations for which the number of illness cases would be 0, with the most common number of illness cases being 5 (of 100 exposed). These effects maintained statistical significance from 106Shigellaper hand down to as low as 100 Shigellaper hand, with some evidence to support lower levels. This quantitative microbial risk assessment shows that antibacterial hand treatments can significantly reduce Shigellarisk.

Cross-contamination between foods and surfaces in food processing environments and home kitchens may play a significant role in foodborne disease transmission. This study quantifies the cross-contamination rates between a variety of fresh-cut produce and common kitchen surfaces (ceramic, stainless steel, glass, and plastic) using scenarios that differ by cross-contamination direction, surface type, produce type, and drying time/moisture level. A five-strain cocktail of rifampin-resistant Salmonellawas used in transfer scenarios involving celery, carrot, and watermelon, and a five-strain cocktail of rifampin-resistant Escherichia coliO157:H7 was used in transfer scenarios involving lettuce. Produce or surface coupons were placed in buffer-filled filter bags and homogenized or massaged, respectively, to recover cells. The resulting solutions were serially diluted in 0.1% peptone and surface plated onto tryptic soy agar with 80 μg/ml rifampin and bismuth sulfite agar with 80 μg/ml rifampin for Salmonellaor sorbitol MacConkey agar with 80 μg/ml rifampin for E. coliO157:H7. When the food contact surface was freshly inoculated, a high amount (>90%) of the inoculum was almost always transferred to the cut produce item. If the inoculated food contact surfaces were allowed to dry for 1 h, median transfer was generally >90% for carrots and watermelon but ranged from <1 to ∼70% for celery and lettuce. Freshly inoculated celery or lettuce transferred more bacteria (∼2 to ∼25% of the inoculum) compared with freshly inoculated carrots or watermelon (approximately <1 to 8%). After 1 h of drying, the rate of transfer from inoculated celery, carrot, and lettuce was <0.01 to ∼5% and <1 to ∼5% for watermelon. Surface moisture and direction of transfer have the greatest influence on microbial transfer rates.

The objective of this study was to evaluate the relationship between prevalence of Listeria monocytogenesas an outcome and Listeriaspp. as an explanatory variable by food products, food contact surfaces, and nonfood contact surfaces in seafood processing plants by using peer-reviewed published data. Nine sets of prevalence data of L. monocytogenesand Listeriaspp. were collected from published studies and used for the analyses. Based on our analysis, the relationship between L. monocytogenesprevalence and Listeriaspp. prevalence in food products (incoming raw materials and finish products) was significant (P= 0.04) with (low) R2= 0.36. Furthermore, Listeriaspp. were not a good indicator for L. monocytogeneswhen testing food contact surfaces (R2= 0.10). Listeriaspp. were a good indicator for L. monocytogenesonly on nonfood contact surfaces (R2= 0.90). On the other hand, the presence of Listeriaspp. on food contact surfaces (R2= 0.002) and nonfood contact surfaces (R2= 0.03) was not a good indicator for L. monocytogenespresence in food products. In general, prevalence of Listeriaspp. does not seem to be a good indicator for L. monocytogenesprevalence in seafood processing plants.

Ceviche is a raw fish dish common in Peru and other Latin American counties. The most characteristic feature of ceviche is the use of lime juice for marinating or “cooking” the raw fish. Confirmed cases of cholera in Peru, New Jersey, and Florida have been associated with ceviche. Although the effect of organic acids on pathogenic bacteria has been well characterized, few data exist on the effect of these acids in seafood systems. The objective of the study was to evaluate the effects of lime juice marination on pathogens likely to be present in ceviche. Tilapia (Oreochromis niloticus) fillet pieces were inoculated with Vibrio parahaemolyticusand Salmonella enterica(.7 log CFU/g) and incubated at 25 and 4°C for 30 or 120 min in the presence of fresh lime juice at concentrations typical for the preparation of ceviche. Similar levels of cells were also inoculated into fresh lime juice without tilapia. Surviving cells were enumerated on selective (xylose lysine Tergitol 4 and thiosulfate-bile-citrate-sucrose) and nonselective (tryptic soy agar) media. V. parahaemolyticuslevels were reduced to below detection limits (∼5-log reduction) under all conditions studied. Salmonellastrains on tilapia were much more resistant to inactivation and were only slightly reduced (∼1- to 2-log reduction). Salmonellaand V. parahaemolyticusinoculated directly into lime juice without tilapia were all reduced to below detection limits (∼5-log reduction). A typical ceviche recipe reduces V. parahaemolyticusrisk significantly but is less effective for control of S. enterica.

This document describes the development of a tool to manage the risk of the transportation of cold food without temperature control. The tool uses predictions from ComBase predictor and builds on the 2009 U.S. Food and Drug Administration Model Food Code and supporting scientific data in the Food Code annex. I selected Salmonellaspp. and Listeria monocytogenesas the organisms for risk management. Salmonellaspp. were selected because they are associated with a wide variety of foods and grow rapidly at temperatures >17°C. L. monocytogeneswas selected because it is frequently present in the food processing environment, it was used in the original analysis contained in the Food Code Annex, and it grows relatively rapidly at temperatures <17°C. The suitability of a variety of growth models under changing temperature conditions is largely supported by the published literature. The ComBase predictions under static temperature conditions were validated using 148 ComBase database observations for Salmonellaspp. and L. monocytogenesin real foods. The times and temperature changes encompassed by ComBase Predictor models for Salmonellaspp. and L. monocytogenesare consistent with published data on consumer food transport to the home from the grocery store and on representative foods from a wholesale cash and carry food service supplier collected as part of this project. The resulting model-based tool will be a useful aid to risk managers and customers of wholesale cash and carry food service suppliers, as well as to anyone interested in assessing and managing the risks posed by holding cold foods out of temperature control in supermarkets, delis, restaurants, cafeterias, and homes.