Publications by authors named "Donald Schaffner"

113 Publications

Wet vs. dry inoculation methods have a significant effect of Listeria monocytogenes growth on many types of whole intact fresh produce.

J Food Prot 2021 Jun 11. Epub 2021 Jun 11.

Rutgers University Food Science 65 Dudley Road UNITED STATES New Brunswick NJ 08901 732-407-7729.

L. monocytogenes causes relatively few outbreaks linked to whole fresh produce but triggers recalls each year in the US. There are limited data on the influence of wet vs. dry methods on pathogen growth on whole produce. A cocktail of five L. monocytogenes strains that included clinical, food, or environmental isolates associated with foodborne outbreaks and recalls was used. Cultures were combined to target a final wet inoculum concentration of 4-5 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), Roseaceae (sweet cherry), Solanaceae (tomato), Brassaceae (cauliflower and broccoli) and Apiaceae (carrot). Intact, whole 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 6 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 was 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 (vs. dry inoculum) resulted in markedly increased L. monocytogenes growth rate and growth magnitude on whole produce surfaces. This difference was highly influenced by temperature with 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, post-harvest, transportation, or retail) should be investigated.
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http://dx.doi.org/10.4315/JFP-21-187DOI Listing
June 2021

Models for factors influencing pathogen survival in low water activity foods from literature data are highly significant but show large unexplained variance.

Food Microbiol 2021 Sep 17;98:103783. Epub 2021 Mar 17.

Department of Food Science, Rutgers University, 65 Dudley Road, New Brunswick, NJ, 08901, USA. Electronic address:

Factors that control pathogen survival in low water activity foods are not well understood and vary greatly from food to food. A literature search was performed to locate data on the survival of foodborne pathogens in low-water activity (<0.70) foods held at temperatures <37 °C. Data were extracted from 67 publications and simple linear regression models were fit to each data set to estimate log linear rates of change. Multiple linear stepwise regression models for factors influencing survival rate were developed. Subset regression modeling gave relatively low adjusted R values of 0.33, 0.37, and 0.48 for Salmonella, E. coli and L. monocytogenes respectively, but all subset models were highly significant (p < 1.0e-9). Subset regression models showed that Salmonella survival was significantly (p < 0.05) influenced by temperature, serovar and strain type, water activity, inoculum preparation method, and inoculation method. E. coli survival was significantly influenced by temperature, water activity, and inoculum preparation. L. monocytogenes survival was significantly influenced by temperature, serovar and strain type, and inoculum preparation method. While many factors were highly significant (p < 0.001), the high degrees of variability show that there is still much to learn about the factors which govern pathogen survival in low water activity foods.
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http://dx.doi.org/10.1016/j.fm.2021.103783DOI Listing
September 2021

Mycotoxins in artisanal beers: An overview of relevant aspects of the raw material, manufacturing steps and regulatory issues involved.

Food Res Int 2021 03 11;141:110114. Epub 2021 Jan 11.

Laboratory of Microbial Processes in Foods, Department of Food Engineering, Center of Technology, Federal University of Paraíba, Campus I, João Pessoa, PB 58051-900, Brazil. Electronic address:

The consumption of artisanal beer has increased worldwide. Artisanal beers can include malted or unmalted wheat, maize, rice and sorghum, in addition to the basic ingredients. These grains can be infected by toxigenic fungi in the field or during storage and mycotoxins can be produced if they find favorable conditions. Mycotoxins may not be eliminated throughout the beer brewing and be detected in the final product. In addition, modified mycotoxins may also be formed during beer brewing. This review compiles relevant information about mycotoxins produced by Aspergillus, Fusarium and Penicillium in raw material of artisanal beer, as well as updates information about the production and fate of mycotoxins during the beer brewing process. Findings highlight that malting conditions favor the production of mycotoxins by the fungi contaminating cereals. Therefore, good agricultural and postharvest mitigation strategies are the most effective options for preventing the growth of toxigenic fungi and the production of mycotoxins in cereals. However, the final concentration of mycotoxin in artisanal beer is difficult to predict as it depends on the initial concentration contained in the raw material and the processing conditions. The current lack of limits of mycotoxins in artisanal beer underestimates possible risks to human health. In addition, modified mycotoxins, not detected by conventional methods, may be formed in artisanal beers. Maximum tolerated limits for these contaminants must be urgently established based on scientific data about transfer of mycotoxins throughout the artisanal beer brewery process.
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http://dx.doi.org/10.1016/j.foodres.2021.110114DOI Listing
March 2021

Scientific Evidence Supports the Use of Alcohol-Based Hand Sanitizers as an Effective Alternative to Hand Washing in Retail Food and Food Service Settings When Heavy Soiling Is Not Present on Hands.

J Food Prot 2021 May;84(5):781-801

Department of Food Science, Rutgers University, 65 Dudley Road, New Brunswick, New Jersey 08901, USA (ORCID: https://orcid.org/0000-0001-9200-0400).

Abstract: 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.

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http://dx.doi.org/10.4315/JFP-20-326DOI Listing
May 2021

ComBase Models Are Valid for Predicting Fate of Listeria monocytogenes on 10 Whole Intact Raw Fruits and Vegetables.

J Food Prot 2021 Apr;84(4):597-610

Department of Food Science, 65 Dudley Road, Rutgers University, New Brunswick, New Jersey 08901.

Abstract: Listeria monocytogenes was 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. monocytogenes behavior 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. monocytogenes strains 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. monocytogenes was able to grow on the whole intact surface of all produce tested, except for carrot. The 10 produce commodities supported growth of L. monocytogenes at 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. monocytogenes growth 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. monocytogenes on fresh whole produce.

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http://dx.doi.org/10.4315/JFP-20-327DOI Listing
April 2021

Quantification of Survival and Transfer of Salmonella on Fresh Cucumbers during Waxing.

J Food Prot 2021 Mar;84(3):456-462

Department of Food Science, Rutgers University, New Brunswick, New Jersey 08901, USA.

Abstract: 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 Salmonella on waxed and unwaxed cucumbers and the potential for Salmonella cross-contamination during the waxing process. Fresh waxed or unwaxed cucumbers were spot inoculated with a cocktail of Salmonella enterica strains. Three different wax coatings (mineral oil, vegetable oil, or petroleum wax) were manually applied to unwaxed cucumbers using polyethylene brushes. Salmonella transfer from inoculated cucumbers to the brush or to uninoculated cucumbers was quantified. Higher Salmonella concentrations 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 Salmonella inoculated directly into waxes, with a significant decline in Salmonella populations 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. Salmonella cells 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). Salmonella remaining on contaminated cucumbers after waxing could be detected for up to 7 days, and Salmonella survived better on cucumbers treated with a petroleum-based wax. These findings should be useful in managing the risk of Salmonella contamination in cucumbers during postharvest handling.

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http://dx.doi.org/10.4315/JFP-20-375DOI Listing
March 2021

A predictive growth model for Clostridium botulinum during cooling of cooked uncured ground beef.

Food Microbiol 2021 Feb 10;93:103618. Epub 2020 Aug 10.

Department of Food Science, Rutgers University, 54 Dudley Road, New Brunswick, NJ, 08901-8520, USA.

A dynamic model to predict the germination and outgrowth of Clostridium botulinum spores in cooked ground beef was presented. Raw ground beef was inoculated with a ten-strain C. botulinum spore cocktail to achieve approximately 2 log spores/g. The inoculated ground beef was vacuum packaged, cooked to 71 °C to heat shock the spores, cooled to below 10 °C, and incubated isothermally at temperatures from 10 to 46 °C. C. botulinum growth was quantified and fitted into the primary Baranyi Model. Secondary models were fitted to maximum specific growth rate and lag phase duration using Modified Ratkowsky equation (R 0.96) and hyperbolic function (R 0.94), respectively. Similar experiments were also performed under non-isothermal (cooling) conditions. Acceptable zone prediction (APZ) analysis was conducted on growth data collected over 3 linear cooling regimes from the current study. The model performance (prediction errors) for all 22 validation data points collected in the current work were within the APZ limits (-1.0 to +0.5 log CFU/g). Additionally, two other growth data sets of C. botulinum reported in the literature were also subjected to the APZ analysis. In these validations, 20/22 and 10/14 predictions fell within the APZ limits. The model presented in this work can be employed to predict C. botulinum spore germination and growth in cooked uncured beef under non-isothermal conditions. The beef industry processors and food service organizations can utilize this predictive microbial model for cooling deviations and temperature abused situations and in developing customized process schedules for cooked, uncured beef products.
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http://dx.doi.org/10.1016/j.fm.2020.103618DOI Listing
February 2021

Validation of a Simple Two-Point Method To Assess Restaurant Compliance with Food Code Cooling Rates.

J Food Prot 2021 Jan;84(1):6-13

Department of Food Science, Rutgers University, 65 Dudley Road, New Brunswick, New Jersey 08901 (ORCID: https://orcid.org/0000-0001-9200-0400 [D.W.S.]).

Abstract: 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) R2 values. 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.

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http://dx.doi.org/10.4315/JFP-20-257DOI Listing
January 2021

Modeling aflatoxin B production by Aspergillus flavus during wheat malting for craft beer as a function of grains steeping degree, temperature and time of germination.

Int J Food Microbiol 2020 Nov 7;333:108777. Epub 2020 Jul 7.

Department of Food Engineering, Technology Center, Federal University of Paraíba, João Pessoa, Brazil. Electronic address:

This study aimed to model the aflatoxin B (AFB) production by A. flavus in wheat grains during malting for craft beer. A total of sixty-four different combinations of grains steeping degree (ST; 41, 43, 45 and 47%), temperature (13, 15, 17 and 19 °C) and time of germination (48, 72, 96 and 120 h), comprising the range of malting conditions that allow the production of quality malt, were assayed. AFB was produced in a range of 15.78 ± 3.54 μg/kg (41% ST, 13 °C for 48 h) to 284.66 ± 44.34 μg/kg (47% ST, 19 °C for 120 h). The regression model showing an acceptable fit to the experimental data (adjusted R 0.84) for AFB as a function of grains steeping degree, temperature and time of germination. Results showed that AFB levels in wheat malt increase with increase of the temperature or time of germination. Within the range of tested malting conditions, no significant effects were observed for steeping degree on AFB levels in wheat malt. The generated model is useful to estimate the AFB levels in wheat malt. Findings highlight overall that if wheat grains are contaminated with A. flavus, AFB might be produced in malt in levels above the limits set by regulatory agencies, regardless the steeping conditions used.
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http://dx.doi.org/10.1016/j.ijfoodmicro.2020.108777DOI Listing
November 2020

Modeling the Inactivation of Viruses from the Family in Response to Temperature and Relative Humidity in Suspensions or on Surfaces.

Appl Environ Microbiol 2020 09 1;86(18). Epub 2020 Sep 1.

Risk Assessment Department, French Agency for Food, Environmental and Occupational Health and Safety, Maisons-Alfort, France.

Temperature and relative humidity are major factors determining virus inactivation in the environment. This article reviews inactivation data regarding coronaviruses on surfaces and in liquids from published studies and develops secondary models to predict coronaviruses inactivation as a function of temperature and relative humidity. A total of 102 values (i.e., the time to obtain a log reduction of virus infectivity), including values for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), were collected from 26 published studies. The values obtained from the different coronaviruses and studies were found to be generally consistent. Five different models were fitted to the global data set of values. The most appropriate model considered temperature and relative humidity. A spreadsheet predicting the inactivation of coronaviruses and the associated uncertainty is presented and can be used to predict virus inactivation for untested temperatures, time points, or any coronavirus strains belonging to and genera. The prediction of the persistence of SARS-CoV-2 on fomites is essential in investigating the importance of contact transmission. This study collects available information on inactivation kinetics of coronaviruses in both solid and liquid fomites and creates a mathematical model for the impact of temperature and relative humidity on virus persistence. The predictions of the model can support more robust decision-making and could be useful in various public health contexts. A calculator for the natural clearance of SARS-CoV-2 depending on temperature and relative humidity could be a valuable operational tool for public authorities.
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http://dx.doi.org/10.1128/AEM.01244-20DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7480392PMC
September 2020

Behavior of Listeria monocytogenes in the presence or not of intentionally-added lactic acid bacteria during ripening of artisanal Minas semi-hard cheese.

Food Microbiol 2020 Oct 5;91:103545. Epub 2020 May 5.

CIMO Mountain Research Centre, School of Agriculture, Polytechnic Institute of Bragança, Bragança, Portugal.

The fate of Listeria monocytogenes during ripening of artisanal Minas semi-hard cheese, as influenced by cheese intrinsic properties and by autochthonous (naturally present) or intentionally-added anti-listerial lactic acid bacteria (LAB) was modeled. Selected LAB strains with anti-listerial capacity were added or not to raw or pasteurized milk to prepare 4 cheese treatments. Counts of LAB and L. monocytogenes, pH, temperature and water activity were determined throughout cheese ripening (22 days, 22±1ᵒC). Different approaches were adopted to model the effect of LAB on L. monocytogenes: an independent approach using the Huang primary model to describe LAB growth and the linear decay model to describe pathogen inactivation; the Huang-Cardinal [pH] model using the effect of pH variation in a dynamic tertiary approach; and the Jameson-effect with N model which simultaneously describes L. monocytogenes and LAB fate. L. monocytogenes inactivation occurred in both treatments with added LAB and inactivation was faster in raw milk cheese (-0.0260 h) vs. pasteurized milk cheese (-0.0182 h), as estimated by the linear decay model. Better goodness-of-fit was achieved for the cheeses without added LAB when the Huang primary model was used. A faster and great pH decline was detected for cheeses with added LAB, and the Huang-Cardinal [pH] model predicted higher pathogen growth rate in cheese produced with raw milk, but greater L. monocytogenes final concentration in pasteurized milk cheese. The Jameson-effect model with N predicted that LAB suppressed pathogen growth in all treatments, except in the treatment with pasteurized milk and no LAB addition. The Huang-Cardinal [pH] model was more accurate in modeling L. monocytogenes kinetics as a function of pH changes than was the Jameson-effect model with N as a function of LAB inhibitory effect based on the goodness-of-fit measures. The Jameson-effect model may however be a better competition model since it can more easily represent L. monocytogenes growth and death. This study presents crucial kinetic data on L. monocytogenes behavior in the presence of competing microbiota in Minas semi-hard cheese under dynamic conditions.
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http://dx.doi.org/10.1016/j.fm.2020.103545DOI Listing
October 2020

Evaluating the Behavior of Staphylococcus aureus and Bacillus cereus in Dairy- and Non-Dairy-Based Aqueous Slurries during Manufacturing of Table Spreads.

J Food Prot 2020 Oct;83(10):1801-1811

JRD Food Technology Consulting, LLC, 5514 North 160th Avenue, Omaha, Nebraska 68116, USA.

Abstract: High-moisture slurries used in the production of table spreads may permit growth of Staphylococcus aureus and Bacillus cereus and 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. aureus and B. cereus in 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. aureus and B. cereus. Samples were individually inoculated with multiple strains of S. aureus and B. cereus to achieve a target level of 102 to 103 CFU/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. aureus and B. cereus using Baird-Parker agar and mannitol yolk polymyxin agar, respectively. Neither S. aureus nor B. cereus exceeded (P < 0.05) proposed food safety limits (105 CFU/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.

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http://dx.doi.org/10.4315/JFP-20-060DOI Listing
October 2020

Successive exposure to Mentha piperita L. essential oil affects the culturability and induces membrane repair in a persister epidemic Salmonella Typhimurium PT4.

Microb Pathog 2020 Dec 25;149:104264. Epub 2020 May 25.

Department of Food Engineering, Center for Technology, Federal University of Paraiba, Campus I, 58051-900, Brazil. Electronic address:

This study had as aims to evaluate the effects of successive exposures to Mentha piperita L. essential oil (MPEO) on culturability and physiological functions of Salmonella Typhimurium PT4. S. Typhimurium PT4 cells (10 log CFU/mL) were exposed to the same (1.25 μL/mL) or increasing MPEO concentrations (1.25-80 μL/mL) during 252 h. At each 36-h interval, the viable cell counts, and distinct cell functions were assessed using plate counting and flow cytometry, respectively. As the exposure time to the same MPEO concentration increased, the population of S. Typhimurium PT4 cells with damaged, permeabilized and depolarized membrane, and compromised efflux activity decreased. Otherwise, S. Typhimurium PT4 cells with damaged membrane physiological functions increased over the exposure to increasing concentrations of MPEO. Genomic analyses showed that the strain carries 17 genes associated with stress responses and the persistence of the tested strain among sources associated with poultry spanning more than 16 years and its virulence for humans. Therefore, successive exposure to a sublethal concentration of MPEO induced S. Typhimurium PT4 cells capable of maintaining the membrane integrity and its functions despite their non-culturable state.
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http://dx.doi.org/10.1016/j.micpath.2020.104264DOI Listing
December 2020

Modification of a Predictive Model To Include the Influence of Fat Content on Salmonella Inactivation in Low-Water-Activity Foods.

J Food Prot 2020 May;83(5):801-815

Department of Food Science, Rutgers University, New Brunswick, New Jersey 08901, USA.

Abstract: Low-water-activity (aw) foods (including those containing fat) are often implicated in outbreaks of Salmonella spp. The influence of fat content on survival in foods such as peanut butter remains unclear. Certain Salmonella serovars 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 Salmonella in low-aw foods 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 aw values (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 aw on 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 aw range 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 aw influenced 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-aw foods containing fat.

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http://dx.doi.org/10.4315/0362-028X.JFP-18-431DOI Listing
May 2020

Modelling Growth and Decline in a Two-Species Model System: Pathogenic O157:H7 and Psychrotrophic Spoilage Bacteria in Milk.

Foods 2020 Mar 12;9(3). Epub 2020 Mar 12.

Department of Food Science, Rutgers University, New Brunswick, NJ 08901, USA.

Shiga toxin-producing O157:H7 is a food-borne pathogen and the major cause of hemorrhagic colitis. is the genus most frequent psychrotrophic spoilage microorganisms present in milk. Two-species bacterial systems with O157:H7 non-pathogenic , and in skimmed milk at 7, 13, 19, or 25 °C were studied. Bacterial interactions were modelled after applying a Bayesian approach. No direct correlation between 's growth rate and its effect on the maximum population densities of species was found. The results show the complexity of the interactions between two species in a food model. The use of natural microbiota members to control foodborne pathogens could be useful to improve food safety during the processing and storage of refrigerated foods.
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http://dx.doi.org/10.3390/foods9030331DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7142549PMC
March 2020

Production of aflatoxin B and B by Aspergillus flavus in inoculated wheat using typical craft beer malting conditions.

Food Microbiol 2020 Aug 8;89:103456. Epub 2020 Feb 8.

Laboratory of Microbial Processes in Foods, Department of Food Engineering, Center of Technology, Federal University of Paraíba, Campus I, João Pessoa, PB, 58051-900, Brazil. Electronic address:

The production of aflatoxin (AF) B and B was determined during malting of wheat grains artificially contaminated with a toxigenic A. flavus strain (CCDCA 11553) isolated from craft beer raw material. Malting was performed in three steps (steeping, germination and kilning) following standard Central European Commission for Brewing Analysis procedures. AFB and AFB were quantified in eleven samples collected during the three malting steps and in malted wheat. Both, AFB and AFB were produced at the beginning of steeping and detected in all samples. The levels of AFB ranged from 229.35 to 455.66 μg/kg, and from 5.65 to 13.05 μg/kg for AFB. The AFB increased during steeping, while no changes were observed in AFB Otherwise, AFB decreased during germination and AFB did not change. AFB and AFB increased after 16 h of kilning at 50 °C and decreased at the end of kilning, when the temperature reached 80 °C. The levels of AFB wheat malt were lower than those detected in wheat grains during steeping; however, levels of both AFB (240.46 μg/kg) and AFB (6.36 μg/kg) in Aspergillus flavus inoculated wheat malt exceeded the limits imposed by the regulatory agencies for cereals and derived products.
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http://dx.doi.org/10.1016/j.fm.2020.103456DOI Listing
August 2020

Quantification of Salmonella enterica transfer between tomatoes, soil, and plastic mulch.

Int J Food Microbiol 2020 Mar 13;316:108480. Epub 2019 Dec 13.

Department of Food Science, Rutgers, the State University of New Jersey, 65 Dudley Road, New Brunswick, NJ 08901, United States of America. Electronic address:

Tomatoes have been linked to Salmonella outbreaks in the United States (US). Plasticulture systems, that combine raised beds, plastic mulch, drip irrigation and fumigation, are common in commercial staked fresh tomato production in the US. The US FDA Produce Safety Rule prohibits the distribution of any produce covered by the rule (including fresh market tomatoes) that drops to the ground before harvest. This research was undertaken to better characterize the risks posed by tomatoes that touch plastic mulch or soil immediately before or during harvest. Research was conducted in three states (Florida, Maryland, and Ohio). Each state utilized tomatoes from their state at the point of harvest maturity most common in that state. Each state used indigenous soil and plastic mulch for transfer scenarios. New plastic mulch obtained directly from the application roll and used plastic mulch that had been present on beds for a growing season were evaluated. A five-strain cocktail of Salmonella enterica isolates obtained from tomato outbreaks was used. Mulch (new or used), soil, or tomatoes were spot inoculated with 100 μl of inoculum to obtain a final population of ~6 log CFU/surface. Items were either touched to each other immediately (1-2 s) after inoculation (wet contact) or allowed to dry at ambient temperature for 1 h or 24 h (dry contact). All surfaces remained in brief (1-5 s) or extended (24 h) contact at ambient temperature. Transfer of Salmonella between a tomato and plastic mulch or soil is dependent on contact time, dryness of the inoculum, type of soil, and contact surface. Transfer of Salmonella to and from the mulch and tomatoes for wet and 1 h dry inocula were similar with mean log % transfers varying from 0.7 ± 0.2 to 1.9 ± 0.1. The transfer of Salmonella between soil or plastic mulch to and from tomatoes was dependent on moisture with wet and 1 h dry inocula generally yielding significantly (p < 0.05) higher transfer than the 24 h dry inoculum. Results indicate that harvesting dry tomatoes significantly (p < 0.05) reduces the risk of contamination from soil or mulch contact. Transfer to tomatoes was generally significantly greater (p < 0.05) from new and used plastic mulch than from soil. If contamination and moisture levels are equivalent and contact times are equal to or <24 h before harvest, significantly (p < 0.05) more Salmonella transfers to tomatoes from mulch than from soil. Our findings support that harvesting tomatoes from soil has similar or lower risk than harvesting from plastic mulch.
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http://dx.doi.org/10.1016/j.ijfoodmicro.2019.108480DOI Listing
March 2020

Growth and Survival of on Intact Fruit and Vegetable Surfaces during Postharvest Handling: A Systematic Literature Review.

J Food Prot 2020 Jan;83(1):108-128

Department of Food Science & Technology, Eastern Shore Agricultural Research and Extension Center, Virginia Tech, Painter, Virginia 23420.

may 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 on 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: 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 growth and survival on intact produce surfaces differ substantially by commodity. Parameters such as temperature and produce surface characteristics had a considerable effect on growth and survival dynamics. This review provides an inventory of the current data on growth and/or survival on intact produce surfaces. Identification of which intact produce commodities support growth and/or survival at various conditions observed along the supply chain will assist the industry in managing contamination risk.
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http://dx.doi.org/10.4315/0362-028X.JFP-19-283DOI Listing
January 2020

Evaluating the Risk of Salmonellosis from Dry Roasted Sunflower Seeds.

J Food Prot 2020 Jan;83(1):17-27

Food Science Department, Rutgers University, 65 Dudley Road, New Brunswick, New Jersey 08901, USA.

Outbreaks and recalls related to nuts and seeds in the United States have increased recently, and 80% of these recalls are due to . 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 during processing of saltwater brined in-shell sunflower seeds. The goal of this research was to validate the adequacy of roasting in controlling during the production of sunflower seeds and to assess the resulting risk. Four strains 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 inactivation and water activity change were developed. The inactivation model predicted a 5-log reduction in when 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 . 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 .
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http://dx.doi.org/10.4315/0362-028X.JFP-19-171DOI Listing
January 2020

Quantifying the Influence of Relative Humidity, Temperature, and Diluent on the Survival and Growth of .

J Food Prot 2019 Dec;82(12):2135-2147

Department of Food Science, Rutgers University, 65 Dudley Road, New Brunswick, New Jersey 08901, USA.

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 on stainless steel, polyvinyl chloride, and ceramic tile. Although surface type had little effect on survival, temperature had a clear effect. survival 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.
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http://dx.doi.org/10.4315/0362-028X.JFP-19-261DOI Listing
December 2019

Modeling the Risk of Salmonellosis from Consumption of Peanuts in the United States.

J Food Prot 2019 Apr;82(4):579-588

3 Department of Food Science, Rutgers University, 65 Dudley Road, New Brunswick, New Jersey 08901, USA.

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 Salmonella on 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 Salmonella cells. 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, Salmonella starting concentration, Salmonella starting 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 Salmonella survival 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.
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http://dx.doi.org/10.4315/0362-028X.JFP-18-314DOI Listing
April 2019

A comparison of dynamic tertiary and competition models for describing the fate of Listeria monocytogenes in Minas fresh cheese during refrigerated storage.

Food Microbiol 2019 Jun 15;79:48-60. Epub 2018 Nov 15.

CIMO Mountain Research Center, School of Agriculture, Polytechnic Institute of Bragança, Bragança, Portugal.

This study compares dynamic tertiary and competition models for L. monocytogenes growth as a function of intrinsic properties of a traditional Brazilian soft cheese and the inhibitory effect of lactic acid bacteria (LAB) during refrigerated storage. Cheeses were prepared from raw or pasteurized milk with or without the addition of selected LAB with known anti-listerial activity. Cheeses were analyzed for LAB and L. monocytogenes counts, pH and water activity (a) throughout cold storage. Two approaches were used to describe the effect of LAB on L. monocytogenes: a Huang-Cardinal model that considers the effect of pH and a variation in a dynamic kinetic analysis framework; and microbial competition models, including Lotka-Volterra and Jameson-effect variants, describing the simultaneous growth of L. monocytogenes and LAB. The Jameson-effect with γ and the Lotka-Volterra models produced models with statistically significant coefficients that characterized the inhibitory effect of selected LAB on L. monocytogenes in Minas fresh cheese. The Huang-Cardinal model [pH] outperformed both competition models. Taking a change into account did not improve the fit quality of the Huang-Cardinal [pH] model. These models for Minas soft cheese should be valuable for future microbial risk assessments for this culturally important traditional cheese.
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http://dx.doi.org/10.1016/j.fm.2018.11.004DOI Listing
June 2019

Changes of Antibiotic Resistance Phenotype in Outbreak-Linked Salmonella enterica Strains after Exposure to Human Simulated Gastrointestinal Conditions in Chicken Meat.

J Food Prot 2018 11;81(11):1844-1850

1 Department of Food Engineering, Center for Technology (ORCID: http://orcid.org/0000-0002-7771-0479 [M.M.]).

Fifteen outbreak-linked Salmonella enterica strains 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 Salmonella strains with reduced susceptibility to ciprofloxacin (CIP) changed to CIP resistant. The ceftriaxone (CTX)-intermediate Salmonella Newport strain changed to CTX resistant. The ampicillin (AMP)-susceptible Salmonella Heidelberg strain changed to AMP resistant, and the sulfamethoxazole-trimethoprim (SXT)-susceptible strains of Salmonella serovars Typhimurium, Agona, Newport, Albany, and Corvallis changed to SXT resistant. The Salmonella Heidelberg, Salmonella Newport, Salmonella Albany, and Salmonella Corvallis 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. enterica strains to clinically relevant antibiotics and should be considered in the selection of therapies for human salmonellosis.
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http://dx.doi.org/10.4315/0362-028X.JFP-18-213DOI Listing
November 2018

Intrinsic Parameters and Bacterial Growth Prediction in a Brazilian Minimally Ripened Cheese (Coalho) during Refrigerated Storage.

J Food Prot 2018 11;81(11):1800-1809

1 Laboratório de Microbiologia de Alimentos, Departamento de Nutrição, Universidade Federal da Paraíba, João Pessoa, Paraíba, 58051-900 Brazil.

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 ( Lactobacillus spp., Lactococcus spp., Enterococcus spp., Staphylococcus spp., 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, Pseudomonas spp., and Yersinia enterocolitica. Grmax values predicted for Escherichia coli, Salmonella spp., and Staphylococcus aureus were 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.
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http://dx.doi.org/10.4315/0362-028X.JFP-18-265DOI Listing
November 2018

Characterization of Microbial Inactivation Using Plasma-Activated Water and Plasma-Activated Acidified Buffer.

J Food Prot 2018 09;81(9):1472-1480

Department of Food Science, Rutgers, The State University of New Jersey, 65 Dudley Road, New Brunswick, New Jersey 08901, USA.

This work investigates the efficacy of plasma-activated water (PAW) and plasma-activated acidified buffer (PAAB) on Enterobacter aerogenes in 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. aerogenes was 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.
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http://dx.doi.org/10.4315/0362-028X.JFP-17-487DOI Listing
September 2018

Prevalence of Human Noroviruses in Commercial Food Establishment Bathrooms.

J Food Prot 2018 05;81(5):719-728

1 Clemson University, Clemson, South Carolina 29634, USA.

Although transmission of human norovirus in food establishments is commonly attributed to consumption of contaminated food, transmission via contaminated environmental surfaces, such as those in bathrooms, may also play a role. Our aim was to determine the prevalence of human norovirus on bathroom surfaces in commercial food establishments in New Jersey, Ohio, and South Carolina under nonoutbreak conditions and to determine characteristics associated with the presence of human norovirus. Food establishments (751) were randomly selected from nine counties in each state. Four surfaces (underside of toilet seat, flush handle of toilet, inner door handle of stall or outer door, and sink faucet handle) were swabbed in male and female bathrooms using premoistened macrofoam swabs. A checklist was used to collect information about the characteristics, materials, and mechanisms of objects in bathrooms. In total, 61 (1.5%) of 4,163 swabs tested were presumptively positive for human norovirus, 9 of which were confirmed by sequencing. Some factors associated with the presence of human norovirus included being from South Carolina (odd ratio [OR], 2.4; 95% confidence interval [CI], 1.2 to 4.9; P < 0.05) or New Jersey (OR, 1.7; 95% CI, 0.9 to 3.3; 0.05 < P < 0.10), being a chain establishment (OR, 1.9; 95% CI, 1.1 to 3.3; P < 0.05), being a unisex bathroom (versus male: OR, 2.0; 95% CI, 0.9 to 4.1; 0.05 < P < 0.10; versus female: OR, 2.6; 95% CI, 1.2 to 5.7; P < 0.05), having a touchless outer door handle (OR, 3.3; 95% CI, 0.79 to 13.63; 0.05 < P < 0.10), and having an automatic flush toilet (OR, 2.5, 95% CI, 1.1 to 5.3; 0.05 < P < 0.10). Our findings confirm that the presence of human norovirus on bathroom surfaces in commercial food establishments under nonoutbreak conditions is a rare event. Therefore, routine environmental monitoring for human norovirus contamination during nonoutbreak periods is not an efficient method of monitoring norovirus infection risk.
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http://dx.doi.org/10.4315/0362-028X.JFP-17-419DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6361381PMC
May 2018

Selection of indigenous lactic acid bacteria presenting anti-listerial activity, and their role in reducing the maturation period and assuring the safety of traditional Brazilian cheeses.

Food Microbiol 2018 Aug 12;73:288-297. Epub 2018 Feb 12.

Department of Food Science, School of Food Engineering, University of Campinas, Campinas, SP, Brazil. Electronic address:

Artisanal raw milk cheeses are highly appreciated dairy products in Brazil and ensuring their microbiological safety has been a great need. This study reports the isolation and characterization of lactic acid bacteria (LAB) strains with anti-listerial activity, and their effects on Listeria monocytogenes during refrigerated shelf-life of soft Minas cheese and ripening of semi-hard Minas cheese. LAB strains (n = 891) isolated from Minas artisanal cheeses (n = 244) were assessed for anti-listerial activity by deferred antagonism assay at 37 °C and 7 °C. The treatments comprised the production of soft or semi-hard Minas cheeses using raw or pasteurized milk, and including the addition of selected LAB only [Lactobacillus brevis 2-392, Lactobacillus plantarum 1-399 and 4 Enterococcus faecalis (1-37, 2-49, 2-388 and 1-400)], L. monocytogenes only, selected LAB co-inoculated with L. monocytogenes, or without any added cultures. At 37 °C, 48.1% of LAB isolates showed anti-listerial capacity and 77.5% maintained activity at 7 °C. Selected LAB strains presented a bacteriostatic effect on L. monocytogenes in soft cheese. L. monocytogenes was inactivated during the ripening of semi-hard cheeses by the mix of LAB added. Times to attain a 4 log-reduction of L. monocytogenes were 15 and 21 days for semi-hard cheeses produced with raw and pasteurized milk, respectively. LAB with anti-listerial activity isolated from artisanal Minas cheeses can comprise an additional barrier to L. monocytogenes growth during the refrigerated storage of soft cheese and help shorten the ripening period of semi-hard cheeses aged at ambient temperature.
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http://dx.doi.org/10.1016/j.fm.2018.02.006DOI Listing
August 2018

Influence of Soap Characteristics and Food Service Facility Type on the Degree of Bacterial Contamination of Open, Refillable Bulk Soaps.

J Food Prot 2018 02;81(2):218-225

3 GOJO Industries, Inc., 1 GOJO Plaza #500, Akron, Ohio 44311, USA.

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.
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http://dx.doi.org/10.4315/0362-028X.JFP-17-251DOI Listing
February 2018

Effect of Surface Roughness in Model and Fresh Fruit Systems on Microbial Inactivation Efficacy of Cold Atmospheric Pressure Plasma.

J Food Prot 2017 08;80(8):1337-1346

Department of Food Science, Rutgers, State University of New Jersey, 65 Dudley Road, New Brunswick, New Jersey 08901, USA.

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 (P) 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 (10 CFU/63.64 cm) 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 cm sandpaper surface inactivation) than did the roughest sandpaper (1.56 log CFU/63.64 cm sandpaper 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 cm fruit peel surface inactivation) than did the roughest fresh fruit peel surface (cantaloupe; 0.61 log CFU/63.64 cm fruit 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.
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http://dx.doi.org/10.4315/0362-028X.JFP-17-064DOI Listing
August 2017
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