11 research outputs found

    R√īle de la composition ionique sur le transfert de sucres √† travers des membranes de nanofiltration

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    Le traitement de fluides contenant des solut√©s neutres et des √©lectrolytes constitue un probl√®me d'importance cruciale car la pr√©sence d'√©lectrolyte r√©duit les performances des proc√©d√©s. Ainsi, des √©tudes ont montr√© que l'addition d'√©lectrolyte modifie le transfert des solut√©s neutres √† travers des membranes de nanofiltration. Des travaux ont mis en √©vidence que la modification du transfert des solut√©s neutres varie avec l'hydratation des ions. Nous pr√©sentons ici les r√©sultats obtenus pour des solutions contenant des sucres de masses molaires croissantes (xylose, glucose et saccharose) et des √©lectrolytes √† diff√©rents √©tats d'hydratations (NaCl, Na2SO4, CaCl2 et MgCl2). Le transfert de sucre est √©tudi√© selon deux modes, filtration et diffusion. L'objectif est d'approfondir la compr√©hension des m√©canismes qui gouvernent le transfert de sucres √† travers des membranes de nanofiltration en se focalisant sur le r√īle des ions. Il s'agit de caract√©riser l'hydratation des sucres √† partir de la d√©termination des volumes molaires apparents et d'√©tudier le transfert de sucres √† travers la membrane. Pour un √©lectrolyte donn√© √† diff√©rentes concentrations, une relation quantitative est √©tablie entre la modification du transfert du sucre et son hydratation. Ces r√©sultats sont prometteurs puisqu'ils permettent de valider l'hypoth√®se selon laquelle la variation du transfert du sucre provient de la modification de son hydratation. Des travaux compl√©mentaires devraient permettre d'am√©liorer l'aspect pr√©dictif vis-√†-vis des performances des proc√©d√©s de nanofiltration pour le traitement de fluides contenant en proportion variable des solut√©s organiques et des ions min√©raux.The treatment of fluids containing both neutral solutes and electrolytes is a crucial issue because the presence of electrolyte decreases the process performances. Then, studies have shown that the addition of electrolyte modifies the mass transfer of the neutral solutes through nanofiltration membranes. Some works have pointed out that the neutral solutes transfer varies according to the hydration of ion. We present here the results obtained with solutions containing saccharides of increasing molecular weights (xylose, glucose and sucrose) and electrolytes of various hydrations (NaCl, Na2SO4, CaCl2 and MgCl2). The saccharide transfer is investigated in both filtration and diffusion regime. The purpose is to go further through the understanding of the mechanisms governing the mass transfer of saccharide through nanofiltration membranes with the focus on the role of ions. The saccharide hydration is characterized from the determination of its apparent molar volume and the saccharide transfer through the membrane is investigated. For a given electrolyte at different concentrations, a quantitative relationship is established between the saccharide transfer modification and its hydration. These results are promising since they enable to validate the assumption according to which the saccharide transfer variation arises from its hydration modification. Further work will be devoted to improve the predictive aspect in relation with the performances of the nanofiltration processes applied to the treatment of solutions of different compositions containing both organic and mineral solutes

    Relationship between volumetric properties and mass transfer through NF membrane for saccharide/electrolyte systems

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    Recent studies have shown that unexpected performances can be obtained with NF membranes, when applied to the treatment of solutions containing significant amount of electrolyte. This study deals with the investigation of the mechanisms governing the mass transfer of neutral species through NF membranes with a focus on the role of ions. More precisely, it consists to determine the apparent molar volume of saccharides, which characterizes the hydration state of solutes in presence of electrolyte, and to assess the relationship between these parameters and those characterizing the mass transfer. The transfer of saccharides of increasing molecular weights (xylose, glucose and sucrose) through a NF membrane is studied in a diffusion regime. Different electrolytes (NaCl, Na‚āāSO‚āĄ, CaCl‚āā, MgCl‚āā) are chosen with respect to their hydration level. A specific procedure was developed to dissociate the flux variation due to the modifications of the solute properties and of the membrane material induced by the electrolyte. The results show that the mass transfer modification is mainly due to the influence of the electrolyte on the solute properties. Then, the mass transfer parameters are put in parallel with the apparent molar volume of saccharides measured in solutions of different ionic compositions. For a given electrolyte, Na‚āāSO‚āĄ, a good quantitative relationship is obtained regardless of saccharide nature, concerning the influence of the electrolyte concentration. This result confirms that the saccharide transfer increase can be due to its dehydration in presence of electrolyte. However, from these results, it is not possible to establish a clear relationship regardless of the electrolyte nature

    Pulsed Electric Fields (PEF) as pre-treatment for freeze-drying of plant tissues

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    [EN] The influence of pulsed electric fields (PEF) treatment on freeze-drying for potato and strawberry tissues was investigated. Samples were pre-treated by PEF ( 400 V cm-1) for different treatment times. Freeze-drying was carried out at -17¬įC and 18.4 Pa or 30 Pa for potato and strawberry tissues, respectively. The effects of PEF pre-treatment was compared with intact samples. The drying time was reduced by 35% for potato and 30% for strawberry. The sample rehydration capacity and the electrolytes released during the rehydration were higher for pre-treated samples. Strawberries texture was characterized by the hardness, the cohesiveness and the springiness.Al-Sayed, L.; Boy, V.; Madieta, E.; Mehinagic, E.; Lanoisell√©, J. (2018). Pulsed Electric Fields (PEF) as pre-treatment for freeze-drying of plant tissues. En IDS 2018. 21st International Drying Symposium Proceedings. Editorial Universitat Polit√®cnica de Val√®ncia. 1575-1582. https://doi.org/10.4995/IDS2018.2018.7484OCS1575158

    Pulsed Electric Fields (PEF) as pre-treatment for freeze-drying of plant tissues

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    [EN] The influence of pulsed electric fields (PEF) treatment on freeze-drying for potato and strawberry tissues was investigated. Samples were pre-treated by PEF ( 400 V cm-1) for different treatment times. Freeze-drying was carried out at -17¬įC and 18.4 Pa or 30 Pa for potato and strawberry tissues, respectively. The effects of PEF pre-treatment was compared with intact samples. The drying time was reduced by 35% for potato and 30% for strawberry. The sample rehydration capacity and the electrolytes released during the rehydration were higher for pre-treated samples. Strawberries texture was characterized by the hardness, the cohesiveness and the springiness.Al-Sayed, L.; Boy, V.; Madieta, E.; Mehinagic, E.; Lanoisell√©, J. (2018). Pulsed Electric Fields (PEF) as pre-treatment for freeze-drying of plant tissues. En IDS 2018. 21st International Drying Symposium Proceedings. Editorial Universitat Polit√®cnica de Val√®ncia. 1575-1582. https://doi.org/10.4995/IDS2018.2018.7484OCS1575158

    R√īle de la composition ionique sur le transfert de sucres √† travers des membranes de nanofiltration

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    TOULOUSE3-BU Sciences (315552104) / SudocSudocFranceF

    A Case Study of Turbulent Free Jet Flows Issuing from Rectangular Slots on Process Performances and Quality of Hot-Air-Dried Apple

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    This study deals with the improvement in drying process performances and the quality of the final product for industrial equipment in the food industry. Designers need to optimize the design parameters of devices to create synergies between the greater energy efficiency of the process and high-quality dried products. Air impingement drying was carried out on apple cylinders at 323 K and with air velocities ranging between 30 and 60 m s‚ąí1. The studied drying process presents a particular setup of jets as they are multiple rectangular slot jets issued from triangular nozzles. The effect of four design jet parameters (slot width, nozzle-to-surface height, nozzle-to-nozzle spacing, and airflow) on the drying process performances and the quality of the final product was analyzed and optimized using response surface methodology (RSM). A minimal influence of design jet parameters on the process performances was shown, while an important impact was observed on the quality of dried apple. The slot width and the nozzle-to-nozzle spacing had a significant effect on the textural and functional properties. Predictive models were established and good agreements were found between predictive and observed values. Sorption isotherms were properly modeled by the Guggenheim‚ÄďAnderson‚Äďde Boer (GAB) model

    Air drying of brown algae Sargassum: Modelling and recovery of valuable compounds

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    Human populations in the Caribbean region, suffer recurrently for 12 years from brown tides followed by significant strandings of Sargassum spp. which cause environmental, economic and health issues. Given current interest in new renewable sources of chemicals, proteins, and polymers, this underexploited biomass represents a potential source to be explored in a biorefinery concept. Up the value chain in biorefinery process, seaweeds should be rapidly stabilised. Stabilisation by drying would permit to reduce the storage and transport costs and to obtain a product stable all year round. The aim of this work was to investigate oven drying and air impingement drying at two air velocities (7 and 21 m s‚ąí1) on three species of Sargassum: S. fluitans III, S. natans I and S. natans VIII. The drying kinetics were studied. The apparent diffusivity coefficients were calculated thanks to the Fick‚Äôs diffusional model. Seven thin-layer equations were used to fit drying kinetics, namely Page, Modified Page, Diffusion approach, Verma, Two-term, Midilli-Kucuk and Henderson-Pabis modified. Freeze-drying, as a reference drying method, was applied on Sargassum in order to compare the effects of drying processes on several phytochemical components, which are neutral sugars, proteins, polyphenols, uronic acids and mineral matter. According to these results, air impingement drying was the better process to dry these three Sargassum species, but it also depended on the seaweed chain of valorisation after the stabilisation process
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