19 research outputs found

    COMBINING MODERATE PULSED ELECTRIC FIELDS WITH TEMPERATURE AND WITH ORGANIC ACIDS TO INACTIVATE ESCHERICHIA COLI SUSPENSIONS

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    The aim of this work was to study the efficiency of inactivation of Escherichia coli cells in aqueous suspensions using combined moderate pulsed electric field (PEF) and thermal treatments. The inactivation kinetics of E. coli cells in aqueous suspensions (1 wt%) was monitored using conductometric technique. The electric field strength E was within 5-7.5 kV/cm, the effective PEF treatment time was within 0-0.75 s, the pulse duration ti was within 0.3-1 ms, the medium temperature was 30-50°C, and the time of thermal treatment tT was within 0-7000 s. The organic acid concentration was within 0-0.5 g/L.The damage of E. coli was accompanied by release of intracellular components. The synergy between the PEF and thermal treatments in E. coli inactivation was clearly demonstrated. The damage efficiency was noticeably improved by addition of organic acids, especially lactic acid

    Formulation of a water-in-oil emulsion encapsulating polysaccharides to improve the efficiency of spraying of plant protection products

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    International audienceW/O emulsions were formulated with a vegetable oil and a water phase containing a polysaccharide and glycerol in order to reduce the loss of a phytosanitory product during its spraying on plants and therefore the amount used. Different kinds of polysaccharides were tested (CMC, guar and xanthan) and two kinds of surfactants were used (lecithin and PGPR). The stability of the emulsions was determined by different techniques bottle test, optical microscopy, laser granulometry and differential scanning calorimetry - whose principle is based on the correlation between the freezing temperature of the droplets and their radius. From the experiments performed by varying different parameters, a formulation of a suitable emulsion was developped 3% of CMC in the water phase, 50-70% V/V of water, 10-12% of PGPR. The release within a few minutes of the required amount of CMC in water checked by conductivity was obtained by adding another surfactant commercially named Cynthiorex

    Inactivation des suspensions microbiennes de Saccharomyces cerevisiae et d Escherichia coli par champs électriques pulsés modérés

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    Les objectifs de ce travail sont d'étudier les effets de l'application des champs électriques pulsés modérés variant de 2 à 15 kV/cm sur les suspensions colloïdales d'E. coli et de S. cerevisiae. Le Tween 80 ainsi que les acides organiques sont ajoutés aux suspensions d'E. coli pour étudier l'effet de leurs combinaisons au traitement CEP et un degré de destruction de 8 log est atteint. Le suivi de l'évolution de la conductivité durant le traitement des suspensions de S. cerevisiae est utilisé pour suivre le degré de détérioration des cellules. Les données obtenues par le calcul de la conductivité sont en corrélation avec le comptage sur boîtes de Pétri. L'effet du CEP augmente avec le mélange des suspensions, l'augmentation de la température, l'ajout du surfactant et l'utilisation du traitement en continu. L'effet de la charge initiale en S. cerevisiae est étudié et le phénomène de percolation est mis en évidence. La nature de l'agrégation est expliquée par les mesures du potentiel S.The objectives of this study were to investigate the effects of moderate pulsed electric fields (2 to 7.5 kV/cm) on colloidal suspensions of E. coli and S. cerevisiae. Tween 80 as well as organic acids were added to the E. coli suspensions to study the effects of their combinations to the PEF, and a destruction degree of 8 log was reached. The electrical conductivity measurements during the PEF-treatment of S. cerevisiae suspensions were used to monitor the extent of cell damages. Data obtained for the disintegration in conductivity experiments are found in good correlation with Petri dishes cultures counting. The PEF-induced lethality of the yeast cells increases with the mixing of suspensions, the increase of temperature, the adding of surfactant and the use of continuous treatment chamber. The effect of the yeast cells concentrations is studied and the percolation phenomenon is underlined. The nature of the enhanced aggregation was revealed by the S-potential measurements.COMPIEGNE-BU (601592101) / SudocSudocFranceF

    Application de la mesure de densité de flux de chaleur à la caractérisation du procédé de surgélation des denrées alimentaires

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    La mesure de flux thermique a été appliquée au procédé de congélation. Des protocoles expérimentaux ont été développés pour l'étalonnage, en froid négatif" des fluxmètres en régime permanent et transitoire. Ces capteurs ont ensuite été utilisés lors de la surgélation de végétaux pour mesurer les coefficients d'échange de chaleur locaux. Ensuite, des transducteurs plastiques ont été conçus pour mesurer les coefficients d'échange par fluxmétrie dans différents types de surgélateurs industriels. Les mesures réalisées sont parfaitement corrélées avec les valeurs obtenues par l'utilisation d'autres méthodes plus classiques. En dernier, une analyse des effets conjugués du blanchiment et de la congélation sur la qualité texturale, de couleur et d'exsudation d'eau chez le haricot vert a été réalisée. Les barèmes de blanchiment HTST limitent la dégradation des qualités des produits après décongélation. Les vitesses de congélation rapide favorisent le maintien de la structure du produit.This work deals with heat flux measurement in food freezing processes. First, protocols were developed to calibrate the sensors, at subzero temperatures, submitted to steady and unsteady state heat transfer. Following this, the sens ors were applied directly to vegetables undergoing freezing to measure the local heat transfer coefficients. ln a second application, plastic transducers were conceived to map the variability of the heat transfer coefficients in different industrial freezers. The results are in good agreement with values calculated by classical methods. The final part of this work focused on the conjugated effects of the blanching and the freezing processes on the textural, color and drip loss quality parameters of a vegetable product (green beans). The HTST blanching protocols reduced firmness and color degradation and minimized drip loss after thawing. High freezing rates avoided severe degradation of vegetable tissues.COMPIEGNE-BU (601592101) / SudocSudocFranceF

    Formulation of a water-in-oil emulsion encapsulating polysaccharides to improve the efficiency of spraying of plant protection products

    No full text
    International audienceW/O emulsions were formulated with a vegetable oil and a water phase containing a polysaccharide and glycerol in order to reduce the loss of a phytosanitory product during its spraying on plants and therefore the amount used. Different kinds of polysaccharides were tested (CMC, guar and xanthan) and two kinds of surfactants were used (lecithin and PGPR). The stability of the emulsions was determined by different techniques bottle test, optical microscopy, laser granulometry and differential scanning calorimetry - whose principle is based on the correlation between the freezing temperature of the droplets and their radius. From the experiments performed by varying different parameters, a formulation of a suitable emulsion was developped 3% of CMC in the water phase, 50-70% V/V of water, 10-12% of PGPR. The release within a few minutes of the required amount of CMC in water checked by conductivity was obtained by adding another surfactant commercially named Cynthiorex

    W/O Emulsion Destabilization and Release of a Polysaccharide Entrapped in the Droplets

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    This study was conducted as part of European project VEGEPHY to develop a product for the crop protection purposes. It concerns first the destabilization of a W/O emulsion containing water droplets in which the polysaccharide carboxymethylcellulose (CMC) is trapped, the droplets being dispersed in a vegetable oil made of rapeseed methyl ester. Polyglycerolpolyricinoleate (PGPR) is used as surfactant and glycerol is added to enhance the dispersion of the CMC. The second part is dealing with the study of the release and dilution of the CMC obtained by dilution of the destabilized emulsion in water in order to obtain the required final amount of CMC for practical purposes. The destabilization of the emulsion by the demulsifier (cynthiorex PMH 1125) has been followed by differential scanning calorimetry (DSC) that permits by studying the freezing of the dispersed water to detect the presence of bulk water. The release and dilution in water of the CMC versus time was followed and quantified by measuring the conductivity of the sample. The release kinetic was modeled using a first-order empirical model. The results showed that the release process of the W/O emulsion depends on the concentration of the demulsifier, on the stirring rate, and on the temperature. The optimum amount of the non-ionic surfactant was found to be 10% and the full release of the CMC has been obtained in 600 seconds

    Optimization of oil yield and oil total phenolic content during grape seed cold screw pressing

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    Grape seed oil being industrially obtained'by solvent extraction, in this study we investigate oil extraction from grape seeds by cold screw pressing, as an alternative extraction process. Effect of raw material and process parameters were evaluated using a 12 experiments Taguchi experimental design. Variables were (1) type of grape seeds, (2) preheating temperature (90 and 120 degrees C), (3) screw rotation speed (40 and 70 rpm) and (4) die diameter (10 and 15 mm). The type of grape seed was the most influencing parameter on the studied responses. Screw rotation speed and die diameter only affected the oil yield. Maximum oil yield was observed for type 1 grape seeds (64.3%, o/o). Total oil polyphenol content was also maximal for type 1 seeds with up to 121 mg GAE/kg of oil. Maximum oil yield was 57.3% and 58.8% (o/o) for type 2 and type 3 grape seed respectively and total polyphenol oil content was below 90 mg GAE/kg for these two types of seeds. Additional experiments were carried out on type I seeds to enhance oil yield and oil polyphenol content. Maximal oil yield achieved was 73% (o/o) and total oil polyphenol content was increased up to 26% (153 mg/kg of oil) on the maximum yield obtained with Taguchi design. (C) 2014 Elsevier B.V. All rights reserved

    Anaerobic digestion of grape pomace Biochemical characterization of the fractions and methane production in batch and continuous digesters

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    In this study, we have estimated the biogas and methane production from grape pomace (variety Cabernet Franc). The physical and chemical characteristics of the raw material were determined, and the structural polysaccharides were identified and analyzed by the Van Soest method. Batch anaerobic digestions were carried out to assess the methane production of the grape pomace, pulp and seeds. The obtained cumulative methane productions are 0.125, 0.165 and 0.052 Nm(3) kg COD-1 for grape pomace, pulps and seeds, respectively. The effect of grinding on the methane potential of the substrates, as a mechanical pretreatment, was evaluated. We found that it increased the anaerobic biodegradability for grape pomace, pulp and seeds by 13.1%, 4.8% and 22.2%, respectively. On the other hand, the methane potential of the grape pomace was determined in a laboratory pilot plant (12 L) continuously mixed with an organic loading rate of 2.5 kg COD m(3) d(-1) and a hydraulic retention time of 30 days. The corresponding biogas production was 6.43 x 10(-3) Nm(3) d(-1), with a methane content of 62.3%. Thus, the pilot plant's efficiency compared to that achieved in the batch process was 81.2%. Finally, a significant correlation was found between the biochemical content and methane production. (C) 2016 Elsevier Ltd. All rights reserved
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