Thèse (M.Sc.)--Université Laval, 2004. / Titre de l'écran-titre (visionné le 18 janvier 2005). Bibliogr.

Th.--Sci.--Nancy--I.N.P.L., 1980.

Made available in DSpace on 2014-06-11T19:26:41Z (GMT). No. of bitstreams: 0 Previous issue date: 2003-08Bitstream added on 2014-06-13T19:54:54Z : No. of bitstreams: 1 gibertoni_cf_me_botfca.pdf: 741489 bytes, checksum: 7474d3adb88a17510191046187783563 (MD5) / Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) / O objetivo deste trabalho foi utilizar ultra e microfiltração para clarificação de suco de yacon (Polymnia sonchifolia) na obtenção de xarope rico em frutanos. Procedeu-se um ensaio inicial de ultra e microfiltração de suco de yacon produzido sem que as raízes tivessem sido submetidas a processo de branqueamento. Este ensaio demonstrou que, embora tenha ocorrido clarificação do permeado em função da filtração tangencial, houve escurecimento enzimático das raízes, resultando em produtos mais escuros do que os oriundos de raízes submetidas ao branqueamento. Os ensaios seguintes objetivaram avaliar os processos de filtração tangencial, utilizando-se de temperaturas de 20, 40, 60 e 80°C. Observou-se aumento do fluxo de permeado em função do aumento da temperatura. Análises de umidade, sólidos totais, cinzas, açúcares redutores, acidez total, proteínas, °Brix e pH feitas nos sucos de alimentação, permeados e retentatos, demonstraram que o aumento da temperatura não interferiu nas características químicas dos produtos, embora ocorra clarificação dos permeados. Escolheu-se a temperatura de 40°C para dar continuidade aos trabalhos. Procedeuse a seguir ensaios combinando pressões transmembrana de 2 e 4 bar com velocidades tangenciais de 2 e 4 m/s. Verificou-se que a combinação de pressão transmembrana 2 bar com velocidade tangencial de 4 m/s resultou em maior fluxo de permeado. As análises químicas demonstraram não haver interferência da pressão e velocidade na composição química dos permeados e retentatos, em relação aos sucos de alimentação. Para conhecer a variabilidade de fluxos de permeado durante a operação do piloto foram feitos testes de repetibilidade. As baixas variabilidades de resultados de fluxo médio permitiram concluir que as condições utilizadas... . / The objective of this work was to utilize ultrafiltration and microfiltration techniques for the clarification of yacon (Polymnia sonchifolia) juice, in obtainment of rich contents of fructans syrup. An initial essay of ultrafiltration and microfiltration was carried out with yacon’s juice produced without the submission of the roots to the bleaching process. This essay demonstrated that there was enzymatic browning of the roots, though occurs permeate clarifies due to the tangential filtration, resulting in darker products than the roots submitted to the bleaching process. The next essays seek to evaluate the tangential filtration process, by testing temperatures of 20, 40, 60, and 80oC. It was observed an increase of the permeate flow following the temperature increase. Moisture, total solids, ash, reducer sugars, total acidity, proteins, oBrix, and pH’s analysis of the feed juices, permeates and retentates demonstrated that the temperature rise didn’t interfere in the products chemical attributes, though occurs the clarify of the permeates. The temperature of 40oC was chosen for the continuity of the works. Following essays were made by combination of transmembrane pressure of 2 and 4 bars with tangential velocities of 2 and 4 m/s. It was verified that the transmembrane pressure of 2 bar with tangential velocity of 4m/s combination resulted in a greatest permeate flux. The chemical analysis demonstrated that there isn’t pressure and velocity’s interference in permeates and retentates chemical composition regarding to the feed juices. Repeated tests were made to know the permeate flux variability during the equipment operation. The low variabilities of the medium flux results permitted to conclude that the used conditions can be reproduced without problems. The best combinations of temperature, velocity, and pressure were utilized in essays with crescent Volumetric... (Complete abstract, click electronic address below).

Membrane surface modification is often utilized to combat membrane fouling, i.e., the deterioration of membrane performance with time. Among many modification methods, the effect of coating the surface of a commercial membrane with electrospun nanofibers on the membrane performance has received little attention. In this work, a commercial polyethersulfone (PES) ultrafiltration membrane was modified by electrospinning PVDF hydrophobic nanofibers for different time periods, i.e., 25min, 125min, and 250min, and its effect on the filtration performance was investigated. It was found that coating with the electrospun nanofiber layer enhanced the pure water permeation (PWP) flux. While the fouling of electrospun PES (EPES) membranes was more severe when they filtered Ottawa River (OR) Water or protein solutions, their final flux was still higher than that of the PES membrane. The membranes were further characterized by scanning electron microscopy (SEM), contact angle measurement and pore size and pore size distribution. The relationship between these characteristics and the membrane performance was discussed.

Orientador: Waldemar Gastoni Venturini Filho / Resumo: O objetivo deste trabalho foi utilizar ultra e microfiltração para clarificação de suco de yacon (Polymnia sonchifolia) na obtenção de xarope rico em frutanos. Procedeu-se um ensaio inicial de ultra e microfiltração de suco de yacon produzido sem que as raízes tivessem sido submetidas a processo de branqueamento. Este ensaio demonstrou que, embora tenha ocorrido clarificação do permeado em função da filtração tangencial, houve escurecimento enzimático das raízes, resultando em produtos mais escuros do que os oriundos de raízes submetidas ao branqueamento. Os ensaios seguintes objetivaram avaliar os processos de filtração tangencial, utilizando-se de temperaturas de 20, 40, 60 e 80°C. Observou-se aumento do fluxo de permeado em função do aumento da temperatura. Análises de umidade, sólidos totais, cinzas, açúcares redutores, acidez total, proteínas, °Brix e pH feitas nos sucos de alimentação, permeados e retentatos, demonstraram que o aumento da temperatura não interferiu nas características químicas dos produtos, embora ocorra clarificação dos permeados. Escolheu-se a temperatura de 40°C para dar continuidade aos trabalhos. Procedeuse a seguir ensaios combinando pressões transmembrana de 2 e 4 bar com velocidades tangenciais de 2 e 4 m/s. Verificou-se que a combinação de pressão transmembrana 2 bar com velocidade tangencial de 4 m/s resultou em maior fluxo de permeado. As análises químicas demonstraram não haver interferência da pressão e velocidade na composição química dos permeados e retentatos, em relação aos sucos de alimentação. Para conhecer a variabilidade de fluxos de permeado durante a operação do piloto foram feitos testes de repetibilidade. As baixas variabilidades de resultados de fluxo médio permitiram concluir que as condições utilizadas... (Resumo completo, clicar acesso eletrônico abaixo). / Abstract: The objective of this work was to utilize ultrafiltration and microfiltration techniques for the clarification of yacon (Polymnia sonchifolia) juice, in obtainment of rich contents of fructans syrup. An initial essay of ultrafiltration and microfiltration was carried out with yacon's juice produced without the submission of the roots to the bleaching process. This essay demonstrated that there was enzymatic browning of the roots, though occurs permeate clarifies due to the tangential filtration, resulting in darker products than the roots submitted to the bleaching process. The next essays seek to evaluate the tangential filtration process, by testing temperatures of 20, 40, 60, and 80oC. It was observed an increase of the permeate flow following the temperature increase. Moisture, total solids, ash, reducer sugars, total acidity, proteins, oBrix, and pH's analysis of the feed juices, permeates and retentates demonstrated that the temperature rise didn't interfere in the products chemical attributes, though occurs the clarify of the permeates. The temperature of 40oC was chosen for the continuity of the works. Following essays were made by combination of transmembrane pressure of 2 and 4 bars with tangential velocities of 2 and 4 m/s. It was verified that the transmembrane pressure of 2 bar with tangential velocity of 4m/s combination resulted in a greatest permeate flux. The chemical analysis demonstrated that there isn't pressure and velocity's interference in permeates and retentates chemical composition regarding to the feed juices. Repeated tests were made to know the permeate flux variability during the equipment operation. The low variabilities of the medium flux results permitted to conclude that the used conditions can be reproduced without problems. The best combinations of temperature, velocity, and pressure were utilized in essays with crescent Volumetric... (Complete abstract, click electronic address below). / Mestre

The project was concerned with studying the capability of a micellar-enhanced ultrafiltration system (MEUF) to remove platinum group metal ions namely Pt (lV) and Pd (ll) chloro anions from aqueous industrial waste effluents. South Africa has the world’s largest reserves of platinum group metals (PGMs) and other valuable metals such as manganese, chrome ores, titanium minerals etc. which are required for new automotive and other technologies, including fuel cells, catalytic converters and lighter components. The consistent loss with the industrial waste stream and the toxicological effects of these precious metals led to the need to develop new and effective methods to recover them from industrial waste effluents. With such a wide variety of fields where these PGMs are used and the failure of the traditional techniques namely sedimentation, fermentation etc. to effectively reduce or recover these highly toxic and precious metal ions prior to discharging industrial waste effluents, it is necessary to explore other techniques such as membrane technology that can be used to recover these valuable species from industrial waste streams. The present study involved the use of a cationic surfactant, viz cetylpyridinium chloride, which was introduced into an aqueous solution containing palladium and platinum metal anions. The surfactant forms charged micelles above a certain critical concentration value. The metal anions adsorb onto the available oppositely charged sites on the micelle surfaces and are then able to be retained by a suitable membrane. Hollow fibre ultrafiltration membranes with the MWCO of +/- 10 kD and +/-30nm pore size were used as a filter component in this study. For this MEUF system to be effective, it was vital that the anionic metal ion species adsorbed sufficiently onto the available oppositely charged sites of the micelles and that the micelles were retained efficiently by the membrane. Results obtained during the investigation made it possible to make certain predictions about the micellisation process. It was also found that, it was not only the metal ion: surfactant (M:S) ratio that was critical, but the presence of other electrolytes in the aqueous stream proved to have a huge impact on the capability of the MEUF system. Findings of this research study showed that the MEUF system using cetylpyridinium chloride (CPC) can be used to recover or retain Pt (lV) and Pd (ll) anions from industrial waste effluents. It was also found that PtCl6 2-, due to its greater adsorption capabilities onto the micelle surface than PdCl4 2- or PdCl3(H2O)-, was preferentially retained in neutral medium. This may be exploited as a possible means of separating the two metal ions. The developed system offers the following advantages over some traditional and current methods: simplified unit operation line flow process, smaller amounts of chemical usage and no solid toxic sludge to be disposed of. Applications of this work could be of vital importance in catalytic converter recycling, especially in Port Elizabeth where extensive automobile parts manufacturing occurs.

A concentrate containing up to 73% protein N was recovered from cheese whey by using cellulose acetate ultrafiltration membrances designed to reject solutes larger than 30,000 molecular weight by a continuous washing procedure. Conditions necessary for increasing the ultrafiltration process for cheese whey are reported. Variables include pressure, membrane porosity, feed rate, clarification, temperature and pH. The objective was to prepare whey products with a minimum concentration of monovalent salts and maximum concentration of protein while still maintaining a high flux rate. As expected pH adjustment to 7.0 and clarification at 2000 X g for 5 min were critical in increasing flux rate. However, membrane blockage occurred and gel electrophoresis indicated that (β-casein and αs-casein were the major components responsible yet salts and lactose may also be implicated to a lesser degree. Flux rate increased with temperature but was not affected by pressure. Results indicate that concentrating 3-4X would be practical but higher levels would be uneconomical due to the accumulation of viscous materials on the membrane. Gel filtration showed that whey proteins are retained almost quantitatively in the concentrate while low molecular weight nitrogen containing material pass the membrane into the permeate. / Land and Food Systems, Faculty of / Graduate

La caséine est une protéine d'un grand intérêt en industrie alimentaire en raison de sa valeur nutritionnelle élevée et de ses nombreuses propriétés fonctionnelles. L'électrodialyse avec membrane bipolaire couplée à l'ultrafiltration (EDBM-UF) est une technologie hybride récemment développée comme alternative à l'acidification et l'alcalinisation chimique pour la production de caséines et de caséinates. Cette technologie présente de nombreux avantages, comme le fait d'avoir un impact environnemental plus faible et de générer des caséines d'une grande pureté. Cependant, les propriétés fonctionnelles des ingrédients produits par EDBM-UF n'ont jamais été étudiées. Dans cette étude, les propriétés fonctionnelles et la composition de la caséine et du caséinate obtenus par acidification chimique et par méthode EDBM-UF à partir de lait d'hiver et d'été ont été analysées et comparées. Les résultats obtenus ont démontré que la méthode EDBM-UF génère des caséines et caséinates d'une pureté et d'une fonctionnalité supérieure. En effet, la teneur en protéines de ces ingrédients est supérieure et la teneur en lactose est inférieure. Bien que plusieurs propriétés fonctionnelles soient équivalentes (solubilité, rétention d'eau, propriétés émulsifiantes et capacité gélifiante) entre les caséines et les caséinates obtenus par les deux méthodes, certaines propriétés sont supérieures. Les ingrédients produits par la méthode EDBM-UF possèdent tous une capacité moussante et une stabilité de la mousse supérieure aux ingrédients produits par la méthode chimique. De plus, les caséines obtenues par EDBM-UF possèdent un caractère moins hygroscopique que les caséines obtenues par acidification chimique. Concernant l'impact des saisons, il a été démontré que la caséine produite à partir de lait d'hiver possèdent une meilleure rétention d'eau et une hygroscopicité moindre par rapport à celle provenant du lait d'été. Par conséquent, ces résultats permettent de conclure que les ingrédients EDBM-UF ont une fonctionnalité supérieure ou équivalente à celle des ingrédients chimiques, et que le procédé EDBM-UF pourrait être une alternative plus éco-efficiente à l'acidification chimique. / Caseins represent a wide interest in the food industry due to their nutritional value and functional properties. Electrodialysis with bipolar membrane coupled to ultrafiltration (EDBM-UF) is a hybrid technology recently developed as an alternative to chemical acidification and alkalinization to produce casein and caseinate and presents many advantages, such as having a lower environmental impact and having a higher protein content of casein. However, functional properties of the ingredients produced by EDBM-UF have never been studied. In this study, the functional properties of casein and caseinate obtained by chemical acidification and by EDBM-UF method from winter and summer types of milk have been analyzed and compared. Results show that EDBM-UF generates casein and caseinate with superior purity and functionality. Protein content of these ingredients is higher while lactose content is lower. In addition, although several functional properties are equivalent (solubility, water retention, emulsifying properties and gelation capacity) between the caseins and caseinates produced by both methods, some properties are superior. Indeed, foaming capacity and stability were improved from EDBM-UF ingredients and casein was less hygroscopic. Regarding the seasonal impact, it has been shown that casein produced from winter milk provides casein with better water retention and lower hygroscopicity compared to that obtained from summer milk. Therefore, these results allow to conclude that EDBM-UF ingredients have greater or equivalent functionality than ingredients obtained by chemical acidification and that EDBM-UF process could be an eco-efficient alternative to chemical one.

No description available.

Le travail de thèse présenté dans ce manuscrit a pour objectif de mettre en place un nouveau procédé d’élaboration de membranes à base de chitosane pour le traitement d’effluents acides contenants des ions métallique. Soluble en milieu aqueux acide, le chitosane présente la propriété de gélifier lorsque le pH devient basique, ce qui permet d’envisager l’élaboration de membrane sans solvant organique contrairement aux polymères synthétiques classiques. Par ailleurs, ce travail de thèse s’est intéressé à un procédé original de gélification par voie enzymatique, dans lequel la gélification in-situ de la solution de chitosane permet une structuration contrôlée de la membrane contrairement aux procédés classiques qui donnent lieu à un front de gélification. Une étude des cinétiques de gélification en fonction des paramètres d’élaboration (température et concentration en urée) a mis en évidence que seule la température est significativement influente sur le temps de gélification dès lors que la concentration en urée n’est pas limitante. Un modèle a été mis en place pour décrire la gélification enzymatique du chitosane afin de comprendre les mécanismes des cinétiques réactionnelles et de transferts lors de la formation du gel. Des membranes de chitosane ont ainsi été élaborées par le procédé par voie enzymatique, la porosité de ces membranes ayant été générée avec un agent porogène (PEG 6000) et une réaction d’acétylation du chitosane ayant permis d’obtenir des membranes insolubles en milieu acide. Les membranes obtenues ont été caractérisées en termes de morphologie et de propriétés fonctionnelles (filtration, sorption du Cu(II) comme élément métallique modèle). / The Ph-D work presented in this manuscript aims to develop a new process for elaborate chitosan membranes for treatment of acidic media containing metal ions. Soluble In acidic aqueous media, gelation occurs when the pH becomes basic, allowing elaboration of membrane without the use of organic solvents unlike classical synthetic polymers. Moreover, this Ph-D work has focused on an original process enzymatic gelation which the in-situ gelation of chitosan solution allows a controlled structuration of the membrane unlike conventional processes which leads to a front gelling.A study of gelation time as a function of the elaboration parameters (temperature and urea concentration) highlighted that only the temperature is a main parameter on gelation time since the urea concentration is not limiting. A model was developed to describe the chitosan enzymatic gelation in order to understand mechanisms of reaction kinetics and transfers during the gel formation.Chitosan membranes have been prepared by enzymatic process, the porosity of such membranes have been generated with a blowing agent (PEG 6000) and an acetylation of chitosan having yielded insoluble membranes in acid medium. The resulting membranes were characterized by their morphology and functional properties (filtration, sorption of Cu (II) as model metal element).