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Abstract Time Temperature Indicators (TTIs) constitute smart devices through which the full history of the time-temperature profile of a food is monitored. The objective of the current study was to develop a versatile microbial TTI based on the violacein formation, a violet pigment produced by the microorganism Janthinobacterium sp. during early growth, depending on temperature and intrinsic properties of the growth medium. The TTI system consisted of Tryptic Soy Agar enriched with 1% glycerol, spot-inoculated with the bacterium. Input parameters were the storage temperature, the pH of the medium, the initial concentration of the microorganism and the volume of the spot. Image analysis was used to estimate the color change of the spots. Luminosity (L ⁎) parameter described the color change adequately. The Baranyi model was used to fit the violacein kinetics data (L ⁎ curve) estimating the TTI's endpoint, i.e., the time at which the violet color occurred. Survival analysis was used to analyze the endpoint data assessing the activation energy, E a TTI , and the TTI's endpoint at a reference temperature (t TTI , ref endpoint). The E a TTI and t TTI , ref endpoint (T ref = 0 °C) parameters ranged between 65.1–110.3 kJ/mol and 10.1–107.6, respectively. Based on the estimated E a TTI and t TTI , ref endpoint parameters, a decision can be made on the most suitable combination of pH, initial concentration and spot quantity for monitoring the impact of time-temperature profile of different foods on the occurrence of spoilage. The TTI was validated for spoilage of minced beef meat under isothermal and dynamic storage conditions using data generated in this study. The applicability of the TTI was also evaluated to other meat products, including vacuum packaged cooked meat products, using literature data. Highlights • The microbial agar-spotted TTI may be applicable in a wide range of foods. • TTI response may match with various organisms, packaging types and inhibitors. • Match with spoilage kinetics via adjustment of pH, spot volume, inoculum level • The TTI is highly customizable, simply and cost-effectively. [ABSTRACT FROM AUTHOR]

In situ quantitative data on Listeria monocytogenes survival during storage of vacuum-packaged fermented sausages at various temperatures were collected from the literature to develop a generic predictive model regarding its fate at a specific storage temperature. The development of the tool was based on the z-concept. The time needed for 4D reduction of the pathogen was estimated and its influence by the temperature was further described by linear regression. A secondary model was developed for describing the effect of sausage water activity on the z-concept parameters at the reference temperature. The decision support tool was successfully validated against the studies not used during the development of the model. Based on the model predictions, a decision can be made about the required time of product storage before its distribution to achieve an additional pathogen inactivation. Such tools can be incorporated in a HACCP plan of a food-producing company to assure food safety. [ABSTRACT FROM AUTHOR]

The aims of the present study were to determine the prevalence and levels of Listeria monocytogenes and Escherichia coli O157:H7 in rocket and cucumber samples by deterministic (estimation of a single value) and stochastic (estimation of a range of values) approaches. In parallel, the chromogenic media commonly used for the recovery of these microorganisms were evaluated and compared, and the efficiency of an enzyme-linked immunosorbent assay (ELISA)-based protocol was validated. L. monocytogenes and E. coli O157:H7 were detected and enumerated using agar Listeria according to Ottaviani and Agosti plus RAPID' L. mono medium and Fluorocult plus sorbitol MacConkey medium with cefixime and tellurite in parallel, respectively. Identity was confirmed with biochemical and molecular tests and the ELISA. Performance indices of the media and the prevalence of both pathogens were estimated using Bayesian inference. In rocket, prevalence of both L. monocytogenes and E. coli O157:H7 was estimated at 7% (7 of 100 samples). In cucumber, prevalence was 6% (6 of 100 samples) and 3% (3 of 100 samples) for L. monocytogenes and E. coli O157:H7, respectively. The levels derived from the presence-absence data using Bayesian modeling were estimated at 0.12 CFU/25 g (0.06 to 0.20) and 0.09 CFU/25 g (0.04 to 0.170) for L. monocytogenes in rocket and cucumber samples, respectively. The corresponding values for E. coli O157:H7 were 0.59 CFU/25 g (0.43 to 0.78) and 1.78 CFU/25 g (1.38 to 2.24), respectively. The sensitivity and specificity of the culture media differed for rocket and cucumber samples. The ELISA technique had a high level of cross-reactivity. Parallel testing with at least two culture media was required to achieve a reliable result for L. monocytogenes or E. coli O157:H7 prevalence in rocket and cucumber samples. [ABSTRACT FROM AUTHOR]

The aim of this study was to assess serotype prevalence and biodiversity of Listeria monocytogenes strains isolated from diverse food products, i.e., minced pork, fruits, and vegetables. Three hundred twenty-six samples previously purchased from supermarkets and street markets within the Athens area were studied for L. monocytogenes prevalence. A total of 121 strains were isolated from the 36 samples that were positive for L. monocytogenes. Serotyping was performed with multiplex PCR, and biodiversity was assessed with random amplified polymorphic DNA (RAPD) PCR analysis using M13, UBC155, and HLWL85 as primers and with repetitive element palindromic (rep) PCR analysis using (GTG)5 as the primer. The majority (17 of 22) of the contaminated minced pork samples contained strains identified as serotype 1/2a, either alone or in combination with strains belonging to serotypes 1/2b, 4a, 4c, or 4ab. However, all L. monocytogenes isolates from fruits and vegetables belonged to serotype 4b. Rep-PCR provided better differentiation of the isolates than did RAPD PCR and resulted in discrimination of the isolates into a larger number of unique profiles. Complete differentiation was achieved only with the combination of these subtyping techniques. [ABSTRACT FROM AUTHOR]

A Listeria monocytogenes subgenomic array, targeting 54 genes involved in the adhesion, adaptation, intracellular life cycle, invasion, and regulation of the infection cycle was used to investigate the gene expression patterns of acid- and salt-stressed Listeria cells after exposure to conditions similar to those in gastric and pancreatic fluids. Three L. monocytogenes strains, one laboratory reference strain (EGDe) and two food isolates (wild strain 12 isolated from milk and wild strain 3 isolated from fermented sausage), were used during the studies. Differences in the expressed genes were observed between the gastric and pancreatic treatments and also between the serotypes. Increased transcripts were observed of the genes belonging to the adaptation and regulation group for serotype 4b (strain 12) and to the invasion and regulation group for serotype 1/2a (strain EGDe). Interestingly, no significantly differentially expressed genes were found for serotype 3c (strain 3) in most cases. The genes related to adaptation (serotype 1/2a) and to intracellular life cycle and invasion (serotype 4b) were down-regulated in order to cope with the hostile environment of the gastric and pancreatic fluids. These findings may provide experimental evidence for the dominance of serotypes 1/2a and 4b in clinical cases of listeriosis and for the sporadic occurrence of serotype 3c. [ABSTRACT FROM AUTHOR]

Abstract: In meat slaughterhouses, the enumeration of certain microorganisms as microbiological quality indicators is very important for verifying effectiveness of the Good Hygiene Practices (GHP) and Hazard Analysis Critical Control Points (HACCP) systems. Microbiological testing of final products as part of the HACCP verifying process may provide information that a process is in control. The aim of this work was to exploit the data from a poultry slaughterhouse implementing HACCP and demonstrate an alternative approach to the conventional statistical analysis using the principles of the Six Sigma quality. The data collected on Total Viable, Total Coliforms and Staphylococcus aureus counts were used to construct control charts (X bar–R control chart) and perform process capability analysis. Based on X bar–R control charts, the process was in a statistical control state but this before its automation was not capable since process capability and process performance indices were below 1.00, indicating the production of poultry carcasses with poor microbiological quality. After process automation, the indices were much higher than 2.00, indicating that the process was capable of producing poultry carcasses within the specification limits. [Copyright &y& Elsevier]

Abstract: Minced pork samples (n =150) obtained from butchers'' shops and supermarkets in Greece, during summer (n =75) and winter (n =75), were subjected to microbiological analysis. Microbial counts (log CFU/g) for the parameters tested were: total viable count (TVC), 6.8±1.0; Pseudomonas spp., 6.4±1.2; Brochothrix thermosphacta, 5.9±1.1; lactic acid bacteria, 5.3±1.0; yeasts and moulds, 4.6±0.7; hydrogen sulfide (H2S)-producing bacteria, 4.3±1.3; Enterobacteriaceae, 3.6±1.2; total coliforms, 2.9±1.1; Escherichia coli, 1.4±0.7; Staphylococcus spp., 4.3±1.0; S. aureus, 2.4±0.9, and Listeria spp., 1.4±0.6. The highest correlations were between TVC and pseudomonads, B. thermosphacta and H2S-producing bacteria, while the lowest were between total coliforms and all other groups of microorganisms except Enterobacteriaceae. The type of retail outlet and the seasonality of sampling did not have any significant effects (p >0.05) on minced pork meat quality. Interrelationships between (i) meat quality and shelf life, (ii) hygienic conditions during mince preparation and (iii) personnel hygiene were revealed. [Copyright &y& Elsevier]

Listeria monocytogenes poses a serious threat to public health, and the majority of cases of human listeriosis are associated with contaminated food. Reliable microbiological testing is needed for effective control of this pathogen by the food industry and competent authorities. The aim of this study was to determine the performance of three culture media commonly used for detecting L. monocytogenes in foods. Minced pork meat samples (n = 100) were subjected to microbiological testing for L. monocytogene according to Intemational Organization for Standardization methods 11290-1:1996 and 11290-2:1998 using PALCAM, ALOA, and RAPID'L.mono culture media in parallel. Presence of the pathogen was confirmed by conducting biochemical and molecular tests on the presumptive L. monocytogenes colonies. Performance attributes of sensitivity, specificity, positive and negative predictive values, positive and negative likelihood ratios, diagnostic odds ratios, error odds ratios, receiving operating characteristic (ROC) curve, and area under this curve were calculated from the presence-absence microbiological test results by combining the results obtained from the culture media and confirmative tests. PALCAM had the best performance in terms of positive predictive value (i.e., a positive result indicates high probability of L. monocytogenes presence) but not in terms of sensitivity (i.e., the ability of the medium to detect the pathogen when present). RAPID'L.mono was the most sensitive medium. None of the culture media were perfect for detecting L. monocytogenes in minced pork meat alone. The pathogen was detected in 16, 19, and 26% (apparent prevalence) of the samples by PALCAM, ALOA, and RAPID'L.mono, respectively, although the true prevalence of the pathogen was 22%. These findings indicate that the use of a single culture medium may lead to erroneous determination of the prevalence of L. monocytogenes. [ABSTRACT FROM AUTHOR]

Abstract: The objective of this study was to estimate the test accuracy measures (classification probabilities [CPs], predictive values [PVs], likelihood ratios [LRs] and area under receiving operating characteristic curve [AUC]) of three different culture-dependent methods, commonly used during routine analysis for the detection of the foodborne pathogen Listeria monocytogenes, from a Bayesian perspective. Data from a previous study by Andritsos et al. (2010) were used to define measures of accuracy for the diagnostic tests. Samples of minced pork meat obtained from local markets were tested for L. monocytogenes presence by parallel testing using selective media (PALCAM, ALOA and RAPID''L.mono). Dirichlet distribution, which is the multivariate expression of a Beta distribution, was used to analyze the data. Bayesian analysis determines characteristics of the posterior distribution from available prior information. Results showed that all methods were best at ruling in L. monocytogenes presence than ruling it out. PALCAM seemed to have better performance based on positive PV, positive LR and AUC, but it was not so sensitive as RAPID''L.mono was. Results also showed that none of the media were perfect in detecting L. monocytogenes, i.e. sensitivity and specificity equal to one. Besides, the problem of observing zero counts may be overcome by applying Bayesian analysis, making the determination of a test performance feasible. [Copyright &y& Elsevier]

Abstract: Cheeses, even though characterized as safe for consumption, have been implicated in foodborne outbreaks associated with severe symptoms and high fatality rate. The foodborne pathogens in raw milk originate from the farm environment and direct excretion from animals infected udder, whereas in dairy plants the pathogens may enter via contaminated raw milk, colonize the dairy plant environment and consequently contaminate dairy products. Important source of contamination during the handling and processing might be the workers as well. The objective of this study was to review literature on the prevalence of pathogens in various types of cheese, raw milk and dairy environment, identify sources of contamination and present concisely prevention measures for farm and dairy plant. [Copyright &y& Elsevier]

In the present work, survival of Listeria monocytogenes in the traditional Greek soft, spreadable cheese Katiki was studied throughout the shelf life of the product. Samples of finished cheese were inoculated with a cocktail of five L. monocytogenes strains (ca. 6 log CFU g-1) and stored at 5, 10, 15, and 20°C. Acid-stress adaptation or cross-protection to the same stress was also investigated by inoculation of acid-adapted cells in the product. The results showed that pathogen survival was biphasic. Various mathematical equations (Geeraerd, Cerf, Albert-Mafart, Whiting, Zwietering, and Baranyi models) were fitted to the experimental data. A thorough statistical analysis was performed to choose the best model. The Geeraerd model was finally selected, and the results revealed no acid tolerance acquisition (no significant differences, P > 0.05, in the survival rates of the non-acid-adapted and acid-adapted cells). Secondary modeling (second-order polynomial with a0 = 0.8453, a1 = -0.0743, and a2 = 0.0059) of the survival rate (of sensitive population), and other parameters that were similar at all temperatures (fraction of initial population in the major population = 99.98%, survival rate of resistant population = 0.10 day-1, and initial population = 6.29 log CFU g-1), showed that survival of the pathogen was temperature dependent with bacterial cells surviving for a longer period of time at lower temperatures. Finally, the developed predictive model was successfully validated at two independent temperatures (12 and 17°C). This study underlines the usefulness of predictive modeling as a tool for realistic estimation and control of L. monocytogenes risk in food products. Such data are also useful when conducting risk assessment studies. [ABSTRACT FROM AUTHOR]

Abstract: A cooked, cured meat product is a perishable product spoiled mainly by lactic acid bacteria (LAB). LAB cause discoloration, slime formation, off-odors and off-flavors as the result of their metabolic activity producing various products. These microbial products in conjunction with the microbial population could be used to assess the degree of spoilage of this type of product. The spoilage evaluation was achieved by following a multivariate approach. Cluster analysis, principal component analysis and partial least square regression were employed to associate spoilage with microbiological and physicochemical parameters. The developed model was capable of giving accurate predictions of spoilage describing the spoilage associations. The study might contribute to the improvement of quality assurance systems of meat enterprises. [Copyright &y& Elsevier]

In the present study, the distribution of the shelf life of cooked, cured meat products based on lactic acid bacteria growth and the distribution of the time to cause health risks based on Listeria monocytogenes growth were studied. Growth models, developed and validated on cooked meat products, were used to predict the growth of microorganisms. Temperature data were obtained from retail and home refrigerators. Distribution predictions were conducted by two approaches (time-emperature profiles and Monte Carlo simulation). Time-temperature profiles were more appropriate to be used, because Monte Carlo simulation overestimated the growth of L. monocytogenes. Shelf life was greatly influenced by storage temperature, but initial microbial load had a smaller effect. The expiration date of cooked meat products might be based on only the growth of the spoilage microorganisms, and only when product contamination with L. monocytogenes cell concentrations is high does a product fraction pose health risks for consumers. Sensitivity analysis confirmed that storage temperature and temperature variability were the most important factors for the duration of shelf life. Distributions of shelf life and time to cause health risks give valuable information on the quality and safety of cooked meat products and may be used as practical tools by meat processors. [ABSTRACT FROM AUTHOR]

Listeria monocytogenes NCTC10527 was examined with respect to its nonthermal inactivation kinetics in fermented sausages from four European countries: Serbia-Montenegro, Hungary, Croatia, and Bosnia-Herzegovina. The goal was to quantify the effect of fermentation and ripening conditions on L. monocytogenes with the simultaneous presence or absence of bacteriocin-producing lactic acid bacteria (i.e., Lactobacillus sakei). Different models were used to fit the experimental data and to calculate the kinetic parameters. The best model was chosen based on statistical comparisons. The Baranyi model was selected because it fitted the data better in most (73%) of the cases. The results from the challenge experiments and the subsequent statistical analysis indicated that relative to the control condition the addition of L. sakei strains reduced the time required for a 4-log reduction of L. monocytogenes (t4D). In contrast, the addition of the bacteriocins mesenterocin Y and sakacin P decreased the t4D values for only the Serbian product. A case study for risk assessment also was conducted. The data of initial population and t4D collected from all countries were described by a single distribution function. Storage temperature, packaging method, pH, and water activity of the final products were used to calculate the inactivation of L. monocytogenes that might occur during storage of the final product (U.S. Department of Agriculture Pathogen Modeling Program version 7.0). Simulation results indicated that the addition of L. sakei strains significantly decreased the simulated L. monocytogenes concentration of ready-to-eat fermented sausages at the time of consumption. [ABSTRACT FROM AUTHOR]

Abstract: Lactobacillus curvatus, isolated from a spoiled vacuum-packaged ‘pariza’ type meat product, was used to inoculate modified MRS broth containing sodium lactate, sodium acetate and potassium sorbate in different concentrations, alone or in inter se combinations. Two commercial preparations (MIX 1 and MIX 2) were also used containing combinations of the above antimicrobials. Results from the preservatives addition to the culture medium showed highest antimicrobial activity in the case of the sodium lactate (2%, 3% or 4%), sodium acetate (0.5%) and potassium sorbate (0.15%) combination. Results from the preservatives addition to two types of thermally processed meats showed that sodium lactate and the combination of sodium lactate, sodium acetate and potassium sorbate were the most effective; extending the products shelf life an additional 10 days. Finally, MIX 1 and MIX 2 suppressed the lactic acid bacteria (LAB) growth in the culture medium but not in the final product. [Copyright &y& Elsevier]

In recent years and with the significant advancements in instrumentation for molecular biology methods, the focus of food microbiologists, dealing with pathogenic microorganisms in foods, is shifting. Scientists specifically aim at elucidating the effect that the food composition, as well as the commonly employed preservation/storage techniques throughout the food chain, have on the virulence of pathogens. Quantitative PCR and microarrays are, nowadays, powerful tools used for such determinations. The application of these approaches for the determination of the gene expression in situ, is a new field of research for food microbiologists and provides new information regarding virulence potential of foodborne pathogens. [ABSTRACT FROM AUTHOR]

Abstract: Three low-fatty baby food matrices were fortified with 0.01–0.2mg/kg of phorate, diazinon, chlorpyrifos and methidathion. A “quick, easy, cheap, effective, rugged and safe” – like method (QuEChERS) was used. Quantities of octadecyl (C18) sorbent differed with fortification level and matrix fat, based on central composite experimental design. Quantification was performed by Nitrogen–Phosphorus Detector gas chromatography, using matrix-matched standards. The highest (p <0.05) recoveries were observed for methidathion, the lowest fortification levels for a specific C18 amount and the lowest C18 amounts. In meals containing vegetables (1.9% fat) and lamb (3.0% fat), 180–210mg C18 gave recoveries from 67.0% to 105.0% and absence of co-extracts. Yogurt dessert (4.5% fat) required 200–230mg C18 for similar results. Recoveries could also be predicted with <20% error by a polynomial model. The results suggest that modified QuEChERS could be effectively used in the low-fatty baby meals residue analysis. [Copyright &y& Elsevier]