Quantifying the effects of heating temperature, and combined effects of heating medium pH and recovery medium pH on the heat resistance of Salmonella typhimurium

International audienceThe influence of heating treatment temperature, pH of heating and recovery medium on the survival kinetics of Salmonella typhimurium ATCC 13311 is studied and quantified. From each non-log linear survival curve, Weibull model parameters were estimated. An average shape parameter value of 1.67 was found, which is characteristic of downward concavity curves and is in agreement with values estimated from other S. typhimurium strains. Bigelow type models quantifying the heating temperature, heating and recovery medium pH influences are fitted on scale parameter δ data (time of first decimal reduction), which reflects the bacterial heat resistance. The estimate of zT (4.64 °C) is in the range of values given in the literature for this species. The influence of pH of the heating medium on the scale parameter (zpH: 8.25) is lower than that of the recovery pH medium influence (z′pH: 3.65)

Modelling the influence of palmitic, palmitoleic, stearic and oleic acids on apparent heat resistance of spores of Bacillus cereus NTCC 11145 and Clostridium sporogenes Pasteur 79.3

International audienceHeat resistance of spores is affected by many factors such as temperature, pH, water activity (aw) and others. Previous studies have reported that free fatty acids can affect the germination and growth of bacterial spores. In this study, we investigated the influence of free fatty acids in heating medium or in recovery medium on the heat resistance of spores of Bacillus cereus NTCC 11145 and Clostridium sporogenes Pasteur 79.3. Four free fatty acids were studied: palmitic, palmitoleic, stearic and oleic acid. During thermal treatments, the impact of these FFA in heating media was generally low, but the presence of free fatty acids in the recovery medium highly decreases bacterial spore apparent heat resistance, particularly with unsaturated fatty acids. A mathematical model was developed to describe and quantify the influence of free fatty acids in recovery media on the D-values. The z'FFA parameter values which quantify the impact of free fatty acids were determined. The variation of this parameter value according to the free fatty acid type was compared with MIC value variation given in the literature. The model enables the decrease in D-values in the presence of free fatty acids to be estimated. The high concentrations of free fatty acids in liver or canned duck may explain the microbial stability with low sterilization values applied

Key Factors Determining the Behavior of Pathogens in Dry-Cured Ham after High Pressure Processing

High pressure processing (HPP) inactivates pathogens and increases the safety of ready-to-eat meat products. The high-pressure lethality and the behavior of the surviving cells after HPP depends on process parameters (pressure and time), microorganism and matrix characteristics. The aim of the present study was to quantify the impact of pressure level, water activity (aw), and fat content on the behavior of Salmonella spp. and Listeria monocytogenes during refrigerated storage of dry-cured ham after high-pressure processing. Salmonella enterica serotype London CTC1003 and L. monocytogenes CTC1034 were inoculated at ca. 7 log cfu/g in dry-cured ham of different aw (0.87–0.98), vacuum packaged, pressurized from 300 to 852 MPa for 5 min, and stored at 7 °C for up to 2 months. Salmonella and L. monocytogenes populations were monitored by plate count during the storage of the hams. The gamma concept was used to quantify the individual effects of aw and storage temperature on the pathogen growth/no-growth behavior in pressurized dry-cured ham. The Weibull (inactivation) or Logistic (growth) primary models were fitted to the log change of pathogen levels during storage of dry-cured ham after pressurization. According to the gamma approach, the refrigeration temperature and aw were the main factors limiting the growth of Salmonella and L. monocytogenes, respectively, in dry-cured ham. Under conditions not allowing growth, the effect of increasing pressures on the microbial inactivation depended on the aw of dry-cured ham and the pathogen; dry-cured ham with high fat content with an aw ≥ 0.95 enhanced the inactivation of Salmonella whereas it reduced that of L. monocytogenes. Under conditions allowing growth of L. monocytogenes, the increase in aw from 0.96 to 0.98 reduced the lag time with no apparent impact on the growth rate.info:eu-repo/semantics/publishedVersio

Physiological traits of Penicillium glabrum strain LCP 08.5568, a filamentous fungus isolated from bottled aromatised mineral water

International audiencePenicillium glabrum is an ubiquitous fungus distributed world wide. This fungus is a frequent contaminant in the food manufacturing industry. Environmental factors such as temperature, water activity and pH have a great influence on fungal development. In this study, a strain of P. glabrum referenced to as LCP 08.5568, has been isolated from a bottle of aromatised mineral water. The effects of temperature, aw and pH on radial growth rate were assessed on Czapeck Yeast Agar (CYA) medium. Models derived from the cardinal model with inflection (Rosso et al., 1993 An unexpected correlation between cardinal temperatures of microbial growth highlighted by a new model. J Theor. Bio. 162, 447-463) were used to fit the experimental data and determine for each factor, the cardinal parameters (minimum, optimum and maximum). Precise characterisation of the growth conditions for such a fungal contaminant, has an evident interest to understand and to prevent spoilage of food products

Étude des facteurs non thermiques agissant sur la décroissance microbienne et modélisation

La microbiologie prévisionnelle, permettant de quantifier l évolution de population bactérienne, s est principalement développée dans les domaines de la croissance et de l inactivation thermique. Cependant, il reste de nombreux points non maîtrisés, par exemple le lent déclin d une population durant sa conservation, durant un stress acide ou osmotique ne peut pas être prédit actuellement de façon fiable. Afin de permettre la description du déclin au cours du temps, de population de Listeria monocytogenes et Salmonella typhimurium en fonction des conditions environnementales, une démarche classique en trois étapes est proposée. (i) Un modèle reposant sur une double distribution de Weibull de la résistance bactérienne au stress est développé. Ce modèle dissocie deux sous populations une plus sensible et l autre plus résistante. Il permet de décrire l évolution de l effectif bactérienne dans le temps, et de caractériser la résistance de chaque sous population à la fois en fonction de l état physiologique de la population bactérienne et en fonction de l intensité du stress. (ii) Les influences sur la résistance bactérienne, du pH, de la concentration en acide lactique non dissocié, et en chlorure de sodium, sont modélisées avec prise en compte de la température dans une gamme non létale. Le modèle proposé comporte deux types de paramètres, caractérisant la sensibilité bactérienne aux variations environnementales ou reflétant la résistance d une souche bactérienne dans un milieu donné. (iii) La sensibilité bactérienne ayant été précédemment étudiée en milieu synthétique, quelques cinétiques en aliment permettent d étendre la prédiction de l inactivation des populations bactériennes en fromage frais, vinaigrette et saumure.The predictive microbiology, quantifying the evolution of bacterial population, has been mainly developed in the fields of the growth and of the thermal inactivation. However, the slow decline of a population during storage of food products, during an acid stress or an osmotic stress can not be predicted in a reliable way. To allow the description of the decrease of the population of Listeria monocytogenes and Salmonella typhimurium during time and according to the environmental conditions, a classical method in three steps was proposed : (i) A model based on a double distribution of Weibull of the bacterial resistance in the stress was developed. This model distinguishes two subpopulations, one more sensitive and the other one more resistant. It allows to describe the bacterial evolution according to time, and to characterize the resistance of each subpopulation according to the physiological state of the bacterial population and to the intensity ofthe stress. (ii) The influences on the bacterial resistance, of the pH, of the concentration of undissociated lactic acid, and of sodium chloride, were modelled with taking account of the temperature of incubation in a non lethal range. The model contains two types of parameters characterizing the bacterial sensibility linked to the environmental variations, or translating the specificity of the bacterial resistance according to the type of environment. (iii) The bacterial sensibility, which was previously studied in synthetic medium, some kinetics in food allow to spread the prediction of the inactivation of the bacterial populations in soft white cheese, salad dressing and brine.BREST-BU Droit-Sciences-Sports (290192103) / SudocSudocFranceF

Validation and performance of predictive modelling in foods: Use of prediction confidence bands

International audienceThe validation and the performance of predictive microbiology models are generally evaluated by the use of numerous factors (Af, Bf, RE, etc). These factors are very easy to calculate, but they have numerous limitations. We propose that these factors be associated with or replaced by the use of prediction confidence bands (PCB). We compared four PCBs here based on different assumptions: two asymptotic PCBs, a bootstrap-type PCB and a PCB based on an exact confidence parametric region referred to as the PCBX

Renvoie aux comité ecclésiastique et diplomatique de la conduite de l'évêque de Trèves lors de la séance du 14 décembre 1790

Coroller du Moustoir Louis Jacques. Renvoie aux comité ecclésiastique et diplomatique de la conduite de l'évêque de Trèves lors de la séance du 14 décembre 1790. In: Archives Parlementaires de 1787 à 1860 - Première série (1787-1799) Tome XXI - Du 26 novembre 1790 au 2 janvier 1791. Paris : Librairie Administrative P. Dupont, 1885. p. 476

Lecture par M. Coroller d’une protestation de M. Botherel , ci-devant procureur général syndic des ci-devant états de Bretagne, lors de la séance du 30 mai 1791

Coroller du Moustoir Louis Jacques. Lecture par M. Coroller d’une protestation de M. Botherel , ci-devant procureur général syndic des ci-devant états de Bretagne, lors de la séance du 30 mai 1791. In: Archives Parlementaires de 1787 à 1860 - Première série (1787-1799) Tome XXVI - Du 12 mai au 5 juin 1791. Paris : Librairie Administrative P. Dupont, 1887. pp. 626-627

Lecture du procès verbal de la séance du 11 novembre 1790, lors de la séance du 13 novembre 1790

Coroller du Moustoir Louis Jacques. Lecture du procès verbal de la séance du 11 novembre 1790, lors de la séance du 13 novembre 1790. In: Archives Parlementaires de 1787 à 1860 - Première série (1787-1799) Tome XX - Du 23 octobre au 26 novembre 1790. Paris : Librairie Administrative P. Dupont, 1885. p. 403

Adresses diverses, lors de la séance du 2 décembre 1790

Coroller du Moustoir Louis Jacques. Adresses diverses, lors de la séance du 2 décembre 1790. In: Archives Parlementaires de 1787 à 1860 - Première série (1787-1799) Tome XXI - Du 26 novembre 1790 au 2 janvier 1791. Paris : Librairie Administrative P. Dupont, 1885. pp. 185-186