Temperature Abuse Research Articles

Growth of Listeria monocytogenes Inoculated on Packaged Fresh-Cut Turnips Stored at 4 and 10°C

The ecology of Listeria monocytogenes has been previously investigated in various whole and minimally processed raw vegetables, but not in turnips. A 2018 national Canadian recall for packaged fresh-cut turnips contaminated with L. monocytogenes raised concerns about turnips being able to support the growth of this microorganism. Thus, this study examined the growth potential of L. monocytogenes in fresh-cut turnips stored at 4 and 10°C. The bacterial microbiota of each brand of purchased turnips was also partially determined to evaluate the diversity of bacteria present on the product. Turnips were mist inoculated at an initial level of 3.0 log CFU/g using a five-strain L. monocytogenes cocktail. Samples were then stored at either 4 or 10°C for 10 days, with enumeration occurring at 0, 5, and 10 days. L. monocytogenes did grow on turnips stored at 10°C, with increases ranging from 0.87 to 1.84 log CFU/g over the 10-day storage period (P < 0.05). In contrast, L. monocytogenes was able to survive but not grow on turnips stored at 4°C for 10 days. This study reinforces the importance of strict temperature control within processing, retail, and household consumer settings. Avoiding temperature abuse conditions and storing packaged fresh-cut turnips under refrigerator conditions (≤4°C) can serve as an important hurdle to prevent and/or limit the growth of L. monocytogenes on these products.

Protocol Improvement for RNA Extraction From Compromised Frozen Specimens Generated in Austere Conditions: A Path Forward to Transcriptomics-Pathology Systems Integration.

At the heart of the phenome-to-genome approach is high throughput assays, which are liable to produce false results. This risk can be mitigated by minimizing the sample bias, specifically, recycling the same tissue specimen for both phenotypic and genotypic investigations. Therefore, our aim is to suggest a methodology of obtaining robust results from frozen specimens of compromised quality, particularly if the sample is produced in conditions with limited resources. For example, generating samples at the International Space Station (ISS) is challenging because the time and laboratory footprint allotted to a project can get expensive. In an effort to be economical with available resources, snap-frozen euthanized mice are the straightforward solution; however, this method increases the risk of temperature abuse during the thawing process at the beginning of the tissue collection. We found that prolonged immersion of snap frozen mouse carcass in 10% neutral buffered formalin at 4°C yielded minimal microscopic signs of ice crystallization and delivered tissues with histomorphology that is optimal for hematoxylin and eosin (H&E) staining and fixation on glass slides. We further optimized a method to sequester the tissue specimen from the H&E slides using an incubator shaker. Using this method, we were able to recover an optimal amount of RNA that could be used for downstream transcriptomics assays. Overall, we demonstrated a protocol that enables us to maximize scientific values from tissues collected in austere condition. Furthermore, our protocol can suggest an improvement in the spatial resolution of transcriptomic assays.

An investigation of the survival and/or growth of Clostridioides (Clostridium) difficile in beef stored under aerobic, anaerobic and commercial vacuum packaging conditions at 2 °C and 20 °C

Although primarily considered to be a nosocomial infection, there is mounting evidence that food, including beef products, may be a source of Clostridioides (Clostridium) difficile. The objective of this study was to investigate the behaviour of this pathogen under atmospheric and temperature conditions that may be encountered in vacuum packaged retail beef. Inoculated steaks were stored in air, in low (950 cm3/m2·d· bar), medium (<47 cm3/m2·d· bar) and high barrier (<3 cm3/m2·d· bar) vacuum packs and under anaerobic conditions at 2 °C and 20 °C. At 2 °C a steady decline in C. difficile concentrations was observed over the 32 days of storage, regardless of oxygen conditions. In contrast, in the temperature abuse scenario, the bacterial counts were significantly (P < 0.05) higher in the medium and high barrier packs and under anaerobic conditions after 2 days and increased up to approximately 5 log10 cfu/g by day 8. It was concluded that under chilled conditions, C. difficile will survive, all-be-it at lower concentrations, for extended periods (up to 32 days) but in a temperature abuse scenario these bacteria will grow on beef steaks stored in medium and high barrier vacuum packs and under anaerobic conditions. Given the increase in community acquired C. difficile infections, the potential role of vacuum packaged steaks as a foodborne source of these pathogens requires further investigation.

Evaluation of public health risk for Escherichia coli O157:H7 in cilantro

This study sought to model the growth and die-off of Escherichia coli (E. coli) O157:H7 along the cilantro supply chain from farm-to-fork to investigate its risk to public health. Contributing factors included in the model were on farm contamination from irrigation water and soil, solar radiation, harvesting, and transportation and storage times and temperatures. The developed risk model estimated the microbiological risks associated with E. coli O157:H7 in cilantro and determined the parameters that had the most effect on the estimated number of illnesses per year so future mitigation strategies could be applied. Results showed a similar decrease in the E. coli O157:H7 (median values) concentrations along the supply chain for cilantro grown in both winter and summer weather conditions. With an estimated 0.1% prevalence of E. coli O157:H7 contamination for cilantro post-harvest used for illustration, the model predicted the probability of illness from consuming fresh cilantro as very low with fewer than two illnesses per every one billion servings of cilantro (1.6 × 10−9; 95th percentile). Although rare, 3.7% and 1.6% of scenarios run in this model for summer and winter grown cilantro, respectively, result in over 10 cases per year in the United States. This is reflected in real life where illnesses from cilantro are seen rarely but outbreaks have occurred. Sensitivity analysis and scenario testing demonstrated that ensuring clean and high quality irrigation water and preventing temperature abuse during transportation from farm to retail, are key to reducing overall risk of illness.

Antimicrobial efficacy of white mustard essential oil and carvacrol against Salmonella in refrigerated ground chicken

Essential oils in combination with other antimicrobials can be added to food products to reduce the levels of target microbes lower than the infectious dose required to cause human illness. The purpose of this study was to investigate the antimicrobial efficacy of white mustard essential oil (WMEO) and carvacrol against Salmonella in ground chicken stored at 4 and 10°C. At 4°C, 0.75% WMEO +0.1% carvacrol treatment had significantly lower (P < 0.05) Salmonella at the end of 12-day storage than the control, which contained no antimicrobials. A combination of 0.75% WMEO and 0.01% carvacrol had a bacteriostatic effect against Salmonella in ground chicken samples stored at 10°C for 7 D. The application of the antimicrobials controlled the growth of Salmonella by delaying the exponential phase at temperature abuse and reducing levels of Salmonella to less than the positive control at 4°C. The use of WMEO and carvacrol shows potential in reducing levels of Salmonella under refrigerated conditions and controlling its growth under temperature abuse conditions in raw poultry products. Further research is needed to investigate the toxicity of the compounds and the most efficient way to apply it to a food product to maximize antimicrobial activity.

Growth Rate and Histamine Production of Klebsiella sp. CK02 Isolated from Skipjack Tuna Compared with Morganella morganii ATCC 25830 at Various Incubation Temperatures

One of an important quality parameter in tuna is the level of histamine content. The contamination of histamine in tuna is mainly due to the activity of histidine decarboxylase produced by the bacteria. A rapid growth of histamine producing bacteria is correlated with the practice of temperature abuse during handling. This study aimed to develop predictive growth modeling of two histamine-producing bacteria in the function of temperature. The growth and histamine production of Klebsiella sp. CK02 and Morganella morganii ATCC 25830 at various temperatures were measured in tryptic soy broth histidine (TSBH) and tuna fish infusion broth (TFIB) growth media. Broths were incubated at 4°C and 15°C for 7 days, and at 30°C and 40°C for 24 hours. The Baranyi and Roberts model was used with DMFit to determine primary growth kinectics, and the Ratkowsky square root model to describe bacterial growth rate as a function of temperature. Histamine production was enumerated by the apparent yield factor (pYhis/CFU) value. Growth rate increased with temperature, with a maximum rate at 40°C for Klebsiella sp. CK02 (0.740 log CFU/h) and M. morganii (0.578 log CFU/h). The Tmin for Klebsiella sp. CK02 in TFIB was -8.9°C, indicating better survival in low storage temperature, compare to M. morganii ATCC 25830. In addition, Klebsiella sp. CK02 produced a lower pYhis/CFU at 15 and 30°C compared to M. morganii ATCC 25830.

Temperature-Dependent Growth Characteristics of Bacillus thuringiensis in a Ratatouille Food Model

In contrast to Bacillus cereus, the role of Bacillus thuringiensis in foodborne illness has been controversially discussed. As B. thuringiensis-based biopesticides containing a mixture of crystal toxins and viable spores are widely used, a current European Food Safety Authority opinion underlines the need for additional data to enable risk assessment. However, it is currently poorly understood if B. thuringiensis is able to multiply in food, which is crucial to sound risk assessment. Therefore, the aim of this study was to investigate growth of selected B. thuringiensis strains from food and insecticides in a ratatouille food model. To this end, the growth parameters of three B. thuringiensis strains were determined: insecticide strain ABTS-351 (CH_119, B. thuringiensis serovar kurstaki), insecticide strain ABTS-1857 (CH_121, B. thuringiensis serovar aizawai), and CH_48 (wild-type B. thuringiensis isolated from rosemary), producing extremely high levels of enterotoxins. After an initial drop in colony counts, we observed a statistically significant growth for the tested B. thuringiensis strains between 6 and 24 h at 22, 30, and 37°C, conditions mimicking prolonged holding times. We were also able to show that the enterotoxin overproducer CH_48 can grow up to 108 CFU/g in the ratatouille matrix within 24 h at 37°C. The two midlevel enterotoxin formers ABTS-351 (CH_119) and ABTS-1857 (CH_121) isolated from biopesticides exhibited growth between 6 and 24 h, with one of the strains growing to 107 CFU/g. To our knowledge, this is the first study providing evidence of B. thuringiensis growth in a food model with intact competitive flora. Our findings suggest strain-specific variation and stress the complexity of assessing the risk related to B. thuringiensis in food, indicating that some strains can represent a risk to consumer health when vegetable-based foods are stored under conditions of prolonged temperature abuse.

Viability of Shiga Toxin–producing Escherichia Coli, Salmonella, and Listeria monocytogenes Within Plant Versus Beef Burgers During Cold Storage and Following Pan Frying

The viability of Shiga toxin-producing Escherichia coli (STEC), Salmonella, and Listeria monocytogenes within plant- and beef-based burgers was monitored during storage and cooking. When inoculated (ca. 3.5 log CFU/g) into 15-g portions of plant- or beef-based burgers, levels of STEC and Salmonella decreased slightly (≤0.5-log decrease) in both types of burgers when stored at 4°C, but increased ca. 2.4 and 0.8 log CFU/g, respectively, in plant-based burgers but not beef-based burgers (≤1.2-log decrease), after 21 days at 10°C. For L. monocytogenes, levels increased by ca. 1.3 and 2.6 log CFU/g in plant burgers after 21 days at 4 and 10°C, respectively, whereas pathogen levels decreased slightly (≤0.9-log decrease) in beef burgers during storage at 4 and 10°C. Regarding cooking, burgers (ca. 114 g each) were inoculated with ca. 7.0 log CFU/g STEC, Salmonella, or L. monocytogenes and cooked in a sauté pan. Cooking plant- or beef-based burgers to 62.8°C (145°F), 68.3°C (155°F), or 73.9°C (165°F) delivered reductions ranging from ca. 4.7 to 6.8 log CFU/g for STEC, ca. 4.4 to 7.0 log CFU/g for L. monocytogenes, and ca. 3.5 to 6.7 log CFU/g for Salmonella. In summary, the observation that levels of all three pathogens increased by ca. 1.0 to ca. 2.5 log CFU/g in plant-based burgers when stored at an abusive temperature (10°C) highlights the importance of proper storage (4°C) to lessen risk. However, because all three pathogens responded similarly to heat in plant-based as in beef-based burgers, well-established cooking parameters required to eliminate STEC, Salmonella, or L. monocytogenes from ground beef should be as effective for controlling cells of these same pathogens in a burger made with plant-sourced protein.

Reducing Postharvest Losses of Spinach Stored at Nonoptimum Temperatures with the Implementation of Passive Modified Atmosphere Packaging

Postharvest losses of fresh produce constitute the biggest portion of the total food losses occurring in food chains globally. The main driver behind the postharvest losses of fresh fruits and vegetables is temperature abuse occurring mainly during transportation and storage. This is a particular problem for small-acreage producers, who frequently have limited access to postharvest handling resources like optimum refrigeration conditions. Passive modified atmosphere packaging (MAP) is a relatively inexpensive intervention that does not require specialized equipment and has demonstrated some potential for maintaining the quality and extending the shelf life of fresh produce stored in nonoptimum temperatures. Our objective was to determine the effect of passive MAP on the quality and storage life of spinach (Spinacia oleracea cv. Corvair) when stored in nonoptimum temperatures. Mature spinach leaves (≈320 g) were packaged in passive MAP bags, developed using the BreatheWay technology, and non-MAP produce bags and subsequently stored at 13 or 21 °C. Spinach physical and nutritional quality was evaluated throughout its storage life in terms of overall quality, water loss, leaf tenderness, surface color, chlorophyll content, electrolyte leakage, chlorophyll fluorescence, antioxidant capacity, total phenolic content, and vitamin C content. Spinach that was stored in MAP bags reached headspace equilibrium at ≈6% Ο2 and 11% CΟ2 at 13 °C and ≈4% Ο2 and 8% CΟ2 at 21 °C after 2 days of storage for both temperatures. The spinach stored in passive MAP at 13 or 21 °C demonstrated significantly higher overall quality during storage and 2 and 1 day longer storage life, respectively, when compared with the control. The spinach in passive MAP demonstrated a slower rate of yellowing and water loss during storage. The limiting factor for the spinach stored in MAP was decay due to condensation at 13 °C and yellowing at 21 °C. There were no statistical differences in the examined nutritional quality parameters between the spinach stored in MAP and produce bags. This study shows that passive MAP can be a valuable tool for reducing the food losses occurring in small-acreage fruit and vegetable operations that have limited access to cooling and refrigerated storage.

A farm-to-fork quantitative risk assessment model for Salmonella Heidelberg resistant to third-generation cephalosporins in broiler chickens in Canada

Salmonella Heidelberg resistant to ceftiofur (a third-generation cephalosporin antimicrobial agent) in broiler chicken products pose a risk to public health in Canada. The objective of this study was to assess the extent of that risk and to evaluate the effect of intervention measures along the agri-food chain. A stochastic farm-to-fork quantitative microbial risk assessment model was developed following the Codex Alimentarius Guidelines for Risk Analysis of Foodborne Antimicrobial Resistance. Different scenarios were analyzed to assess the individual relative effects of 18 possible interventions in comparison to a baseline scenario. The baseline scenario represented the first year of on-farm antimicrobial use surveillance in the Canadian broiler industry and the year before an industry-imposed ban on the preventive use of antimicrobials of very high importance to human health (2013), where 31.3% of broiler flocks consisted of birds to which ceftiofur was administered.The baseline scenario predicted an average probability of illness of 1.1 per 100,000 servings (SE: 0.064 per 100,000), corresponding to an average of 22,000 human infections (SE: 1900) with ceftiofur-resistant S. Heidelberg per year, which is likely an overestimation. This risk was reduced by 90% or 20% when two separate scenarios designed to capture the effect of withdrawing preventive ceftiofur use from poultry production were simulated using different approaches; data used for the former scenario were confounded by other potential concomitant control measures (e.g. Salmonella vaccination programme), so the true effect likely lies somewhere between the two estimates. A theoretical ‘worst case’ scenario where all flocks had birds exposed to ceftiofur increased the risk by 107%. A 50% reduction in the probability of human prior exposure to antimicrobials, which has a selective and competitive effect for Salmonella spp. following ingestion of contaminated products, reduced the risk by 65%. Other promising measures that could be considered for further risk management included improved cleaning and disinfection between broiler flocks on farm (risk reduction by 26%), exclusive use of air chilling (risk reduction by 34%), and the improvement of meat storage and preparation conditions, e.g., no temperature abuse at retail (risk reduction by 88%). These findings showed the importance of a structured approach to assessing and potentially implementing effective interventions to reduce the risk associated with ceftiofur-resistant S. Heidelberg at different steps along the agri-food chain.Major data gaps included information on concentrations of resistant bacteria, cross contamination at processing and how ceftiofur-resistant S. Heidelberg behave in comparison with susceptible ones, e.g., in terms of growth and survival ability, as well as pathogenicity and virulence.

Volatile Changes During Storage of Shelf Stable Apple Juice: Integrating GC-MS Fingerprinting and Chemometrics.

This is the first study to reveal potential markers for volatile changes during ambient and accelerated shelf life of pasteurized apple juice. The volatile changes were monitored at 20, 30 and 40 °C using a headspace solid-phase microextraction-gas chromatography-mass spectrometry fingerprinting method. Using modern chemometrics and feature selection, hexanal, trans-2-hexenal, dimethyl sulphide, furfural, ethyl acetate and 1-pentanol were chosen as potential shelf life markers. Volatiles associated with the green, grassy and fresh apple aroma, such as hexanal and trans-2-hexenal, decreased during storage, whereas thermal load and browning associated compounds, like dimethyl sulphide and furfural, increased during storage. Hexanal and trans-2-hexenal can be markers to monitor the change in green-apple like character. Furfural and dimethyl sulphide can be markers of temperature abuse during juice processing and storage. Furfural can also be an indicator for juice browning. The present work effectively identified potential markers to monitor and predict volatile aroma changes of shelf stable apple juice in different storage conditions. Sensory analysis can be conducted in the future to confirm the aroma relevance of selected markers.

The photo-/thermo-chromism of spiropyran in alkanes as a temperature abuse indicator in the cold chain of vaccines

Color change related to the phase change of spiropyran–merocyanine system can indicate temperature changes in vaccine transportation.

Predictive Model of Listeria monocytogenes Growth in Queso Fresco

Listeria monocytogenes is a hardy psychrotrophic pathogen that has been linked to several cheese-related outbreaks in the United States, including a recent outbreak in which a fresh cheese (queso fresco) was implicated. The purpose of this study was to develop primary, secondary, and tertiary predictive models for the growth of L. monocytogenes in queso fresco and to validate these models using nonisothermal time and temperature profiles. A mixture of five strains of L. monocytogenes was used to inoculate pasteurized whole milk to prepare queso fresco. Ten grams of each fresh cheese sample was vacuum packaged and stored at 4, 10, 15, 20, 25, and 30°C. From samples at each storage temperature, subsamples were removed at various times and diluted in 0.1% peptone water, and bacteria were enumerated on Listeria selective agar. Growth data from each temperature were fitted using the Baranyi model as the primary model and the Ratkowsky model as the secondary model. Models were then validated using nonisothermal conditions. The Baranyi model was fitted to the isothermal growth data with acceptable goodness of fit statistics (R2 = 0.928; root mean square error = 0.317). The Ratkowsky square root model was fitted to the specific growth rates at different temperatures (R2 = 0.975). The tertiary model developed from these models was validated using the growth data with two nonisothermal time and temperature profiles (4 to 20°C for 19 days and 15 to 30°C for 11 days). Data for these two profiles were compared with the model prediction using an acceptable prediction zone analysis; >70% of the growth observations were within the acceptable prediction zone (between -1.0 and 0.5 log CFU/g). The model developed in this study will be useful for estimating the growth of L. monocytogenes in queso fresco. These predictions will help in estimation of the risk of listeriosis from queso fresco under extended storage and temperature abuse conditions.

Effect of temperature on the growth of Staphylococcus aureus in ready-to-eat cooked rice with pork floss

Cooked rice with pork floss (CRPF) wrapped in dried seaweed is one of the most popular ready-to-eat (RTE) foods in many Asian countries, particularly in Taiwan. The products are susceptible to Staphylococcus aureus contamination and temperature abuse during manufacturing, distribution, and storage. The objective of this study was to examine the effect of temperature on its growth in RTE CRPF for use in risk assessment and prevention of staphylococcal food poisoning (SFP). Inoculated CRPF samples were stored at 4, 12, 18, 25, and 35°C, and the change in the populations of S. aureus during storage were analyzed using three primary models to determine specific growth rate (μmax), lag-phase duration (λ), and maximum population density (ymax). The Ratkowsky square-root and Huang square-root (HSR) models were used as the secondary models to describe the effect of temperature on μmax, and a linear and an exponential regression models were used to describe the effect of temperature on λ and ymax, respectively. The model performance was evaluated by the root mean square error (RMSE), bias factor (Bf), and accuracy factor (Af) when appropriate. Results showed that three primary models were suitable for describing the growth curves, with RMSE ≤ 0.3 (log MPN/g). Using μmax obtained from the Huang model, the minimum growth temperature (Tmin) estimated by the HSR model was 7.0°C, well in agreement with the reported Tmin. The combination of primary and secondary models for predicting S. aureus growth was validated by additional growth curves at 30°C, which showed that the RMSE was 0.6 (log MPN/g). Therefore, the developed models were acceptable for predicting the growth of S. aureus in CRPF under likely temperature abuse conditions and can be applied to assess the risk of S. aureus in CRPF and design temperature controls to reduce the risk of SFP.

Growth behaviour and thermal inactivation of E. coli O157:H7 and Salmonella spp. in ground lean camel meat

This study aimed to evaluate growth behaviour of Escherichia coli O157:H7, Salmonella spp., and background microbiota in ground lean camel meat during refrigerated storage for up to 7 d, and determine thermal inactivation parameters (D and z-values) of the pathogens in the meat. Fresh ground camel meat samples were individually inoculated with two isolates of each E. coli O157:H7 strains and Salmonella serovars. Inoculated and uninoculated samples were stored aerobically at 4 °C and abusive temperature (10 °C) for 1, 4 and 7 d. Inoculated samples were also heat-treated in a circulating water bath at 55–65 °C. Upon storage for 7 d at 4 °C, the population of E. coli O157:H7 and Salmonella cells decreased significantly in samples. In contrast, samples stored at 10 °C showed significant increases in microbial populations. With storage, the populations of mesophilic lactic acid bacteria, mesophilic total plate counts, yeasts and molds, Pseudomonas spp., as well as Enterobacteriaceae increased significantly. E. coli O157:H7 strains showed average D-values at 57.5 to 65 °C ranging from 1.8 to 0.067 min while Salmonella spp. at 55 to 62.5 °C showed D-values ranging from 2.2 to 0.057 min. The z-values of E. coli O157:H7 strains were 4.6 and 5.0 °C and were 5.1 and 5.5 °C for Salmonella spp. This study provides information to assist food industry and retail meat processors to enhance safety and storage quality of camel meat and facilitate validation of thermal processing of camel meat products.

Performance and conduct of supply chains for United States farmed oysters

Farmed oysters are one of the most valuable aquacultured products in the United States (U.S.), are highly perishable, and increasingly shipped live year-round. Supply chain actors must work together to bring refrigerated oysters to market quickly, while maintaining product value, safety and traceability information. In light of these demands, this study assesses the performance and conduct of supply chains for U.S. farmed oysters (Crassostrea virginica, C. gigas). Over the two-year study period, we conducted interviews with 56 businesses and tracked 125 oyster shipments from two major growing regions in the U.S. through six different types of supply chains. We hypothesized that direct and intermediated supply chains would perform differently in terms of time-to-market, product temperature in cold chains, compliance with temperature regulations, and modeled risks from Vibrio parahaemolyticus. Intermediated supply chains, by their definition have more connections than direct supply chains, and we found this introduces a longer time-to-market and a higher incidence of time and temperature abuse. However, these factors did not lead to greater modeled V. parahaemolyticus risks. Participants in both direct and intermediated supply chains were aware of the importance of traceability and felt uniformly positive about their ability to perform recalls. A common concern was the speed of government-imposed recalls, which can be declared by regulators after the affected live oysters are consumed. Members of these supply chains play different roles in maintaining the cold chain, possess different levels of information related to traceability, and describe different levels of trust with other supply chain actors. This paper contributes to a growing body of knowledge on supply chains for seafood and their critical, and sometimes overlooked, role in larger food systems.

In situ characterisation of biofilms formed by psychrotrophic meat spoilage pseudomonads

Psychrotrophic Pseudomonas species form biofilms on meat during refrigerated and temperature abuse conditions. Biofilm growth leads to slime formation on meat which is a key organoleptic degradation characteristic. Limited research has been undertaken characterising biofilms grown on meat during chilled aerobic storage. In this work, biofilms formed by two key meat spoilage organisms, Pseudomonas fragi and Pseudomonas lundensis were studied in situ using five strains from each species. Biofilm structures were studied using confocal microscope images, cellular arrangement, cell counts and biomass quantifications. This work demonstrated that highly dense, compact biofilms are a characteristic of P. fragi strains. P. lundensis formed biofilms with loosely arranged cells. The cells in P. fragi biofilm appear to be vertically oriented whereas this characteristic was absent in P. lundensis biofilms formed under identical conditions. Despite the continued access to nutrients, biofilms formed on meat by proteolytic Pseudomonas species dispersed after a population maximum was reached.

Dynamic analysis of growth of Salmonella spp. in raw ground beef – Estimation of kinetic parameters, sensitivity analysis, and Markov Chain Monte Carlo simulation

Nontyphoidal Salmonella are major foodborne pathogens often associated with raw and undercooked meats. In this study, a cocktail, containing 6 strains, 5 serovars of Salmonella enterica, was inoculated to raw ground beef to observe the bacterial growth and survival under 6 dynamic temperature profiles ranging from 1 to 47 °C during storage. One-step dynamic analysis was used to directly construct predictive models from dynamic growth curves for both background microbiota and Salmonella.The estimated minimum growth temperature (Tmin) for Salmonella spp. in raw ground beef was 9.9 °C, and its population would gradually decrease at a rate of approximately 0.14 log CFU/g per week per °C below this temperature. Above 17.3 °C, Salmonella would grow faster than the background microbiota. Scaled sensitivity coefficients were calculated to determine the identifiability of the kinetic parameters. The models were validated using dynamic growth curves set aside for validation. The root-mean-square-errors (RMSE) of prediction were identical to those of model development (0.6 log CFU/g) for the deterministic method.Bayesian Markov Chain Monte Carlo (MCMC) simulation was used to generate the posterior distribution of kinetic parameters and to predict the bacterial growth. The results showed that the observed growth data were mostly within the range of mean ± standard deviation of the stochastic predictions. The RMSE of prediction by MCMC analysis was only 0.2 log CFU/g, showing that Bayesian MCMC simulation can be used to more accurately predict the growth of Salmonella spp. in raw ground beef. The results from this study may help conduct more accurate risk assessments of Salmonella spp. in raw ground beef during storage and temperature abuse.

Effect of bag-in-box packaging material on quality characteristics of extra virgin olive oil stored under household and abuse temperature conditions

• Shelf life of EVOO packaged in tin-plated steel containers at 22 °C was 80 days. • Shelf life of EVOO packaged in tin-plated steel containers at 37 °C was 60 days. • Shelf life of EVOO packaged in bag-in-box containers at 22 °C was 120 days. • Shelf life of EVOO packaged in bag-in-box containers at 37 °C was 100 days. • Bag-in-box retains EVOO quality longer than tin-plated steel. The effect of bag-in-box (B) packaging material on quality characteristics of extra virgin olive oil (EVOO) was studied as a function of storage time (0–120 days) and temperature (22 °C and 37 °C). Olive oil packaged in tin-plated steel (S) containers served as control. Olive oil sampling was carried out every 20 days, assessing quality deterioration by monitoring multiple quality parameters: acidity, PV, K 232 , K 270 , ΔK, color, total phenolic content (TPC), FA composition and volatile compounds’ profile. Based mainly on acidity, PV, K 232 , and K 270 values, samples packaged in S could no longer rank as EVOO after 80 days of storage at 22 °C, and after 60 days at 37 °C. Samples stored in B retained EVOO specifications throughout storage at 22 °C and had a 100 days shelf life at 37 °C. Conclusively, results showed that B packaging proved to be more suitable for all olive oil samples even for those exposed to abuse temperatures.

Evaluation of an WPC edible film added with a cocktail of six lytic phages against foodborne pathogens such as enteropathogenic and Shigatoxigenic Escherichia coli

Active packaging materials with antimicrobial properties have gained significant interest over the last decade. Furthermore, phages are potentially useful as antimicrobial agents in food. Phage stability assays were conducted in the whey protein concentrate (WPC) matrix over 5 weeks of storage. In addition, the phages incorporated in the WPC matrix were characterized by their release from films into an aqueous system and solid food, as well as by their antimicrobial activity against pathogenic E. coli in a liquid medium and in meat at refrigerated, room and abusive temperatures. The results demonstrate that phages are highly stable in WPC films within 5 weeks of storage. Moreover, WPC films can release a significant number of phages into an aqueous system and onto a meat surface at similar concentrations. Phage-added films produced a significant reduction in E. coli cells to non-detectable levels in antimicrobial assays. Similar results, such as a complete inactivation achieved for DH5α and O157:H7 STEC strains, were obtained when antimicrobial assays were performed on meat. As a conclusion, the six-phage cocktail added into WPC films was highly stable, effectively released from films and proved highly effective as a biocontrol tool, though not under all the conditions evaluated.