Traitements par hautes pressions hydrostatiques des denrées alimentaires : état de l’art

National audienceHigh Pressure has traditionally been used for many years in the fields of geology and chemistry. This technique was first applied in the food industry, in Japan, in the late 1980s. This technology, also named pascalization, consists in maintaining the product at very high hydrostatic pressure (100-1000 MPa) for a definite time and temperature. The high hydrostatic pressure treatment is considered as a nonthermal process capable of inactivating and eliminating pathogenic and food spoilage microorganisms. This novel technology has great potential improving food safety and extending food products shelf-life while preserving their organoleptic properties. Today, more than 160 industrial vessels are under work and more and more high-pressure-treated products are available in the market. In this paper, effects of high hydrostatic pressure treatment on food constituents and microorganisms are reviewed.L’utilisation de la pression, bien connue dans le monde de la géologie, de la géochimie et de la chimie, a fait son apparition dans les Industries Agro-Alimentaires il y a moins d’une vingtaine d’années en Europe. Le traitement d’aliments par Hautes Pressions Hydrostatiques (HPH), quelquefois dénommé Pascalisation, connaît aujourd’hui un fort et constant développement partout dans le monde. De cette période initiale pionnière, au début des années 1990, à l’existence aujourd’hui de plus de 160 installations industrielles dans le monde et de plus en plus de produits traités par Hautes Pressions Hydrostatiques dans les linéaires de la grande distribution, le chemin parcouru est riche de très nombreuses publications scientifiques ou de vulgarisation s’intéressant le plus souvent aux effets du traitement sur les caractéristiques organoleptiques et technologiques des aliments ou sur les microorganismes d’intérêt. Il nous semble nécessaire et utile, aujourd’hui, d’effectuer une synthèse bibliographique sur ces deux principaux sujets

Assessment of Salmonella and Listeria monocytogenes level in ready-to-cook poultry meat: Effect of various high pressure treatments and potassium lactate concentrations

International audienceThe objective of this study was to develop a probabilistic model in order to determine the contamination level of Salmonella and Listeria monocytogenes in ready-to-cook poultry meat, after a high pressure (HP) treatment. The model included four steps: i) Reception of raw meat materials, mincing and mixing meat, ii) Partitioning and packaging into 200-g modified atmosphere packs, iii) High pressure treatment of the meat, and iv) Storage in chilled conditions until the end of the shelf-life. The model excluded the cooking step and consumption at consumer's home as cooking practices and heating times are highly variable. The initial contamination level of Salmonella and L. monocytogenes was determined using data collected in meat primary processing plants. The effect of HP treatment and potassium lactate on microbial reduction was assessed in minced meat, using a full factorial design with three high pressure treatments (200, 350 and 500 MPa), three holding times (2, 8 and 14 min) and two potassium lactate concentrations (0 or 1.8% w/w). The inactivation curves fitted with a Weibull model highlighted that the inactivation rate was significantly dependent on the HP treatment. From the literature, it was established that Salmonella was not able to grow in the presence of lactate, under modified atmosphere and chilled conditions whereas the growth of L. monocytogenes was determined using an existing model validated in poultry (available in Seafood Spoilage and Safety Predictor software, V. 3.1).Once implemented in the Excel add-in @Risk, the model was run using Monte Carlo simulation. The probability distribution of contamination levels was determined for various scenarios. For an average scenario such as an HP treatment of 350 MPa for 8 min, of 200 g minced meat containing 1.8% lactate (pH 6.1; aw 0.96), conditioned under 50% CO2, the prevalence rate of Salmonella and L. monocytogenes, after a 20-day storage at 6 °C was estimated to be 4.1% and 7.1%, respectively. The contamination level was low considering that the product is going to be cooked by the consumer afterwards: the 99th percentile of the distribution was equal to − 2.3 log cfu/g for Salmonella and 0.5 log cfu/g for L. monocytogenes. More generally, the model developed here from raw material reception up to the end of the shelf-life enables to recommend combinations of HP treatment and lactate formulation to guarantee an acceptable microbial concentration before cooking

DROPLET SIZE AND VELOCITY MEASUREMENTS AT THE OUTLET OF A HOLLOW CONE SPRAY NOZZLE

During the course of a severe accident in a nuclear pressurized water reactor (PWR), hydrogen may be produced by reactor core oxidation and distributed into the containment. Spray systems are used in order to limit overpressure, enhance the gas mixing, avoid hydrogen accumulation, and wash out fission products. In order to simulate these phenomena with computational fluid dynamics codes, it is first necessary to know the droplet size and velocity distributions close to the outlet nozzle. Furthermore, since most of the phenomena relative to droplets (condensation, gas entrainment, and collisions) are of particular importance in the region just below the nozzle, accurate input data are needed for real-scale PWR calculations. The objective is, therefore, to determine experimentally these input data under atmospheric conditions. Experimental measurements were performed on a single spray nozzle, which is routinely set up in many PWRs. This nozzle is generally used with water at a relative pressure supply of 3.5 bar, producing a mass flow rate of approximately 1 kg/s. At a distance of 20 cm, in which under ambient conditions atomization is just achieved, it is found that the geometric mean diameter varies from 280 to 340 μm, the Sauter mean diameter varies from 430 to 520 μm, and the mean axial velocity varies from 14 to 20 m/s. The radial velocity is around 7 m/s, whereas the orthoradial velocity is almost equal to zero at this distance of the nozzle. Gas velocity measurements around the spray are also performed. © 2011 by Begell House, Inc.status: publishe

L'enfant rêvé: Anthologie des théâtres d’éducation du XVIIIe siècle

International audienceL’Enfant rêvé, anthologie de pièces de théâtre destinées à la jeunesse composées et jouées durant le XVIIIe siècle, éclaire la révolution qui s’opère autour de la figure enfantine et adolescente, ses relations avec le monde, ses apprentissages dans un siècle passionné par la pédagogie

Anthologie des théâtres d’éducation du XVIIIe siècle

L’Enfant rêvé, anthologie de pièces de théâtre destinées à la jeunesse composées et jouées durant le XVIIIe siècle, éclaire la révolution qui s’opère autour de la figure enfantine et adolescente, ses relations avec le monde, ses apprentissages dans un siècle passionné par la pédagogie