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Abstract: The purpose of this work was to estimate the prevalence and concentration of Listeria monocytogenes in minced pork meat by the application of a Bayesian modeling approach. Samples (n = 100) collected from local markets were tested for L. monocytogenes using in parallel the PALCAM, ALOA and RAPID’L.mono selective media. Presence of the pathogen was confirmed through biochemical and molecular tests. Independent experiments (n = 10) for validation purposes were performed. No L. monocytogenes was enumerated by direct-plating (<10 CFU/g), though the pathogen was detected in 22% of the samples. Sensitivity and specificity varied depending on the culture method. L. monocytogenes concentration was estimated at 14–17 CFU/kg. Validation showed good agreement between observed and predicted prevalence (error = −2.17%). The use of at least two culture media in parallel enhanced the efficiency of L. monocytogenes detection. Bayesian modeling may reduce the time needed to draw conclusions regarding L. monocytogenes presence and the uncertainty of the results obtained. [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 In the present study, the development of reverse transcription-quantitative polymerase chain reaction protocols for three virulence genes ( plcA, iap and hly) and the sigB stress response gene that may be applied for the determination of the virulence gene expression of Listeria monocytogenes in situ was reported. When applied to L. monocytogenes strains of different origin (#3, isolated from meat; National Collection of Type Cultures 10527, a collection strain; and #162, isolated from cheese) and to four different food matrices (fermented sausage, soft cheese, ultrahigh temperature milk and minced meat), stored at 4 and 12C, significant heterogeneity in their expression was recorded. By statistical analysis of the data, it was possible to determine a significant effect on the gene expression by the food matrix, especially for the strain #162. This work showed that environmental factors may influence the virulence expression of L. monocytogenes providing better insights to the physiology of the microorganism grown in foods. PRACTICAL APPLICATIONS The ability to rapidly determine the virulence potential of Listeria monocytogenes in food is a challenge. This study adds new information regarding the heterogeneity within this species. Moreover, it highlights the need to better understand the influence of the different food matrices on the expression of virulence and stress response genes in L. monocytogenes. The reverse transcription-quantitative polymerase chain reaction approach developed and exploited in this study has the potentials to be applied in the field of food safety in order to provide additional insights regarding the virulence of L. monocytogenes. Such information could be useful in implementing control strategies. [ABSTRACT FROM AUTHOR]

This work aimed to determine the effect of applying different temperatures during the fermentation process of Spanish-style table olives. 'Manzanilla de Sevilla' (southwest of Spain, Badajoz) and 'Manzanilla Cacereña' (northwest of Spain, Caceres) olives were processed at an industrial scale in table olive fermenters whose brine was subjected to different thermal treatments. One of the three conducted experiments found that maintaining brine at 20–24 °C over a 3-month period led to optimum firmness, better color indices, and greater free acidity and lactic acid bacteria populations in comparison to an unheated control. Furthermore, raising the temperature of the fermenter to 20–24 °C accelerated the fermentation process, provoking better lactic bacteria and yeast growth without affecting olive firmness. The higher fermentation rate (shorter time to completion) associated with temperature-controlled olives also reduced the marketing time of the final product. Controlling brine temperature led to a better aspect and color, higher acidity, lower bitterness, and better overall assessment of processed olives. In addition, 'Manzanilla de Sevilla' olives presented a higher phenolic content than 'Manzanilla Cacereña' olives. Preliminary evidence is presented suggesting that 'Manzanilla Cacereña' olives appear highly amenable to Sevillian-style processing. The present innovative work demonstrates the importance of applying different thermal treatments to brine to control the temperature during the industrial fermentation of table olives during the cold season. [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]

Kashkaval of Pindos cheese was successfully produced using 100% sheep milk (KS) or with the addition of 10% goat milk (KG). Urda cheese was manufactured using 100% sheep milk (US) or 90% sheep milk-10% goat (UG) whey from the production of kashkaval of Pindos cheese. Both cheeses were made taking into account their traditional cheese-making methods. The cheeses were assessed for their chemical, microbiological and organoleptic characteristics. Generally, no significant differences were observed between KS and KG cheese and between US and UG cheese regarding their physicochemical, textural characteristics, soluble nitrogen fraction and total fatty acid content. The fat content of Urda cheese was low, in accordance with the demand of consumers for healthy products. KS cheeses showed higher total volatile compounds than KG cheeses at 60 and 90 days of ripening and storage as well as lower counts of thermophilic-mesophilic lactic acid bacteria. No differences were observed in the microbial counts between US and UG cheeses. Acetone, hexanal, 2 heptanone, ethanol and toluene were found in abundance in Urda cheeses. Both kashkaval of Pindos and Urda cheeses received high scores during the organoleptic evaluation. The obtained data may lead to the production of both cheeses with standard characteristic according to the traditional recipes and improve their recognition.