Doctor of Philosophy / Food Science Program / Fadi M. Aramouni / Thomas J. Herald / Dynamic viscoelastic and intrinsic viscosity properties of native xanthan, deacetylated xanthan, guar, and their mixtures in dilute solutions were investigated by using an oscillating capillary rheometer. Influence of mixing temperature, deacetylation, and salt concentration on xanthan conformation and interaction with guar were studied in order to provide additional evidence that can be used to elucidate the mechanism of the intermolecular interaction between the two biopolymers, and build up a more detailed rheological understanding of molecular interactions between xanthan and guar gum in dilute solutions. Synergistic interaction was found at mixing temperatures of 25 and 80 °C, but a stronger synergistic interaction was observed at mixing temperature of 80 °C. The differences in viscosity and elasticity measurements between the two mixing temperatures could be attributed to the degree of disordering of xanthan. For both mixing temperatures, the relative viscosity and elasticity of xanthan and guar blends were higher than the relative viscosity and elasticity calculated for blends assuming no interaction, indicating that intermolecular binding occurred between galactomannans backbone and disordered segments of xanthan. Deacetylated xanthan exhibited a stronger synergistic interaction with guar than native xanthan. The intrinsic viscosities of deacetylated xanthan-guar mixtures were higher than those calculated from the weight averages of the two individually, whereas the intrinsic viscosities of native xanthan-guar mixtures were lower than those calculated from weight averages of the two individually, demonstrating that intermolecular binding occurred between xanthan and guar gum. Synergistic interaction for both native xanthan-guar mixtures and deacetylated xanthan-guar mixtures in the dilute regime was observed in water and 2 mM NaCl but not in 40 mM NaCl. The results suggest that intermolecular interaction has occurred between xanthan and guar mixtures in water and 2 mM NaCl, but may not occur in 40 mM NaCl and mutual incompatibility may take place. These results also suggest that degree of disordering of xanthan played a critical role in xanthan-guar interaction and may explain the differences in viscosity, elasticity, and intrinsic viscosity measurements between 2 and 40 mM NaCl, and hence, the intermolecular interaction occurred between the backbone of guar gum and the disordered segments of xanthan.

A busca por embalagens flexíveis rapidamente degradáveis tem sido intensa nos anos mais recentes. Amidos de variadas fontes têm sido avaliados para a produção de filmes, sendo que a maioria destes apresenta boas características mecânicas e de barreira ao oxigênio, entretanto, uma série de limitações é observada com relação às suas características hidrofílicas e permeabilidade ao vapor d´água. O amido de ervilha normalmente apresenta teores mais elevados de amilose, o que pode melhorar a obtenção da rede formadora de filmes. Além disto, as associações amido-goma podem modificar a gelatinização e retrogradação do amido, processos que interferem na formação de filmes. O acréscimo de plastificantes também tem se mostrado de importância para melhorar as propriedades mecânicas dos filmes. Assim, o objetivo do presente trabalho foi avaliar o efeito da adição de goma xantana e de glicerol ao amido de ervilha verde de alto teor de amilose (cv. Utrillo) na elaboração de filmes e em suas características. Soluções filmogênicas (SF) com diferentes teores de amido de ervilha (3, 4 e 5%), de goma xantana (0, 0,05 e 0,1%) e de glicerol (proporção glicerol-amido de 1:5 p/p) foram estudadas. As SF foram obtidas por ebulição (5 min.), seguida de autoclavagem por 1h. a 120°C. Os filmes foram prepa rados segundo a técnica de casting. O aumento da concentração de amido na solução filmogênica aumentou a espessura, fator de ruptura, resistência à perfuração e solubilidade dos filmes em água. O aumento da concentração da goma xantana interferiu apenas nas propriedades associadas à cor dos filmes, aumentando os valores da tonalidade e decrescendo o croma a* e a transparência. O aumento da concentração do glicerol interferiu nas propriedades mecânicas dos filmes, gerando redução dos valores de resistência máxima à tração, tensão na ruptura, resistência à perfuração e fator de ruptura. O plastificante também gerou aumento do alongamento na ruptura, redução da transparência e aumento da espessura e da solubilidade do filme em água. / In the past few years, the attempt to obtain degradable flexible packaging has increased considerably. In this sense, starches obtained from different botanical sources have been evaluated to produce films. Most of these films present good mechanical characteristics and provide a good barrier to oxygen. Nevertheless, some limitations have been observed in relation to their hydrophilic properties and permeability to water vapor. Studies using starch from green peas with high levels of amylose to produce films were not found in the literature. The higher levels of amylose can improve the achievement of the matrix that forms films. In addition, starch-gum associations can modify starch gelatinization and retrogradation, processes which interfere with film formation. The addition of plasticizers has also been considered important to improve the mechanical properties of films. The aim of this study was to evaluate the effect of the addition of xanthan gum and glycerol to the starch of green peas with high content of amylose (cv. Utrillo) in the preparation of films and in their features. Filmogenic solution (FS) with different levels of pea starch (3, 4 and 5%), xanthan gum (0, 0.05 and 0.1%) and glycerol (glycerol-starch ratio of 1:5 p/p) were tested. The FS was obtained by boiling (5 min.), followed by autoclaving for 1h. at 120°C. The films were prepared by casting. The increased concentration of starch in the solution increased the thickness, factor of rupture, puncture force and solubility of films in water. Increasing amounts of xanthan affected only the properties associated with the color of the films, increasing the values of hue angle and decreasing the chroma a* and transparency. The increased concentration of glycerol interfered in the mechanical properties of the films, causing reduction of the maximum values of tensile strength, strain at break, puncture force and factor of rupture. The plasticizer also caused an increase of elongation at break, reduced transparency and increased thickness of the film and the solubility in water.

Les polysaccharides amphiphiles sont constitués d’un squelette hydrophile sur lequel sont greffés des groupements hydrophobes. Ils possèdent des propriétés rhéologiques accrues dues à leur capacité d’auto-organisation en solution aqueuse mais également interfaciales dues à leurs propriétés d’adsorption aux interfaces eau/huile. Néanmoins, peu d’études s’intéressent à conférer ce type de propriétés à des polysaccharides complexes en termes de structure ou de conformation, comme le xanthane. En effet, ce polymère adopte en solution deux conformations distinctes selon les conditions expérimentales : une forme ordonnée hélicoïdale rigide et une forme désordonnée de type pelote flexible.Partant de ce constat, l’objectif de ce travail de thèse est de déterminer l’impact de la rigidité du squelette du xanthane modifié hydrophobiquement sur les propriétés amphiphiles en solution mais également sur les propriétés stabilisantes en émulsion.Il s’avère que la conformation adoptée par le polymère pendant le processus de greffage a un impact majeur sur ses propriétés rhéologiques : le xanthane modifié sous forme désordonnée possède un caractère associatif, contrairement au xanthane modifié sous forme ordonnée.De plus, le xanthane modifié hydrophobiquement est capable, sous certaines conditions, de former et de stabiliser des émulsions H/E, sans ajout de tensioactif moléculaire, en se partitionnant entre stabilisation de l’interface eau/huile et maintien de la viscosité de la phase aqueuse continue. / Amphiphilic polysaccharides are composed of a hydrophilic backbone grafted with hydrophobic moieties. They show specific rheological properties due to their capacity to self-associate in solution, but also interfacial properties due to their ability to adsorb at the water/oil interface. However, only few studies describe the chemical modification of complex heteropolysaccharides regarding their structure or their conformation, such as xanthan. Indeed, this polysaccharide can adopt in solution two distinct conformations depending on experimental conditions: an ordered rigid helix or a disordered flexible coil.The objective of this work is to determine the impact of the chain stiffness of hydrophobically modified xanthan on associative properties in solution, but also on stabilizing properties in emulsion.The conformation adopted by the polymer during the grafting procedure has a major impact on the rheological properties: xanthan modified under disordered conformation is an associative polysaccharide, contrary to xanthan modified under its ordered conformation.In addition, hydrophobically modified xanthan is able, under certain conditions, to form and stabilize O/W emulsion, without further addition of molecular surfactant, by partitioning between stabilization of the water/oil interface and viscosifying the continuous aqueous phase.

To confirm computer simulations and Computational Fluid Dynamics (CFD) analysis, benchtop experiments are needed with a fluid that mimics blood and its viscoelastic properties. Blood is challenging to use as a working fluid in a laboratory setting because of health and safety concerns. Therefore, a blood analogue is necessary to perform benchtop experiments. Viscosity is an important property of fluids for modeling and experiments. Blood is a shear thinning fluid, so it has a decreasing viscosity with higher shear rates. This project seeks to create a blood mimicking fluid for benchtop laboratory use. Numerous fluids with different combinations of water, glycerin, and xanthan gum were created to mimic the shear thinning property of blood at different hematocrit levels. Since the amount of xanthan gum is very small, an analytical balance was used. To mix the solution, an immersion blender and a heat circulator were used. The data were obtained from 10-90 torque percent, which is the range over which the rheometer is accurate, so the exact ranges of shear rate tested depended on the test fluid. The created solutions were compared to blood at the equivalent hematocrit and previously performed tests.The three different equivalent hematocrits all produced results similar to viscosities of blood. The results were similarly representative of blood at different equivalent viscosities for the 0.0075% xanthan gum and the 0.075% xanthan gum by weight. The solutions were able to mimic the shear thinning behavior of blood at different equivalent hematocrits. The fluids with 0.075% xanthan gum and 50% water and 50% glycerin is a better representative than the fluids with 0.075% xanthan gum and 60% water and 40% glycerin.

No description available.

Le traitement de l’asthme concerne une large population et fait appel très majoritairement à une administration par voie pulmonaire. Cette voie présente certains inconvénients qui pourraient être palliés par le recours à la voie buccale comme envisagé dans cette étude, avec une amélioration attendue de la compliance et de la biodisponibilité. Aussi ce travail a eu pour objectif de développer et caractériser une formulation mucoadhésive thermogélifiante à base de salbutamol. Au regard des contraintes liées à la voie buccale et à la prise en charge du traitement de l’asthme aigu, les principales propriétés pharmacotechniques attendues pour optimiser la biodisponibilité de cette formulation ont été : (i) une gélification optimale autour de 30°C après pulvérisation pour faciliter notamment l’administration ; (ii) des propriétés mécaniques et mucoadhésives importantes pour assurer un maintien de la forme au site d’absorption ; (iii) une cinétique de libération compatible avec le traitement de la phase aigüe de la pathologie. Le choix des excipients a été défini afin d’avoir la plus grande innocuité de la formulation finale. Les travaux expérimentaux ont mis en évidence l’intérêt de certaines techniques innovantes pour la caractérisation de ce type de formulation comme notamment l’étude de libération à l’aide de l’appareil de dissolution à flux continu, la détermination de la cytotoxicité par microscopie holographique digitale et l’évaluation de la mucoadhésion in vitro et in vivo par imagerie. Les résultats ont aussi permis de proposer des modèles mathématiques pour l’interprétation des mécanismes de libération du salbutamol et quantifier l’importance des phénomènes de diffusion et d’érosion. Les conclusions de cette étude sont favorables à la poursuite du développement en vue d’une commercialisation. / The treatment of asthma concerns a large population and generally necessitates an administration by the pulmonary route. This route has some drawbacks which could be overcome by the buccal route, like considered in this study expecting an improvement of the compliance and the bioavailability. The aim of this work was to develop and characterize a thermogelling mucoadhesive formulation containing salbutamol sulfate. The main properties of the formulation were: (i) thermogelation around 30°C to facilitate the administration by spray; (ii) strong mechanical properties and high mucoadhesive strength to maintain the formulation in situ; (iii) drug release kinetics adapted to the treatment. The excipients were selected with regard to the final formulation safety. The experimental work emphasized the great interest of certain techniques in the characterization of this kind of formulation, for example the drug release study using flow through apparatus, the cytotoxicity study using digital holographic microscopy and also the mucoadhesion study by in vivo imaging. The use of mathematical models provided a relevant understanding of drug release mechanisms. The conclusion of this study is favorable to a further development of the project for a future marketing.

O conhecimento de propriedades termofísicas é importante na modelagem, na otimização e no projeto de equipamentos para processos como a fabricação de massa de pão congelada. Neste trabalho, as propriedades termofísicas condutividade térmica, difusividade térmica e calor específico foram determinadas experimentalmente ao longo do processo de congelamento da massa de pão, pois influenciam diretamente a cinética do processo que, por sua vez, determina a qualidade do pão produzido. Os resultados obtidos mostraram que algumas destas propriedades variaram em função do conteúdo inicial de água e principalmente devido à mudança da temperatura. O valor médio encontrado através da atividade de água das massas (aw = 0,950), para temperatura inicial de congelamento, pode explicar alguns desvios no ajuste dos dados experimentais a modelos disponíveis na literatura baseados na lei de Raoult, que são estritamente relacionados à fração de gelo formada. O uso combinado de goma guar e xantana reduziu a entalpia de fusão ao longo do tempo de armazenamento congelado (87,4 J.g-1 e 81,2 J.g-1 para a formulação sem gomas, não congelada e após 28 dias de armazenamento congelado; 84,4 J.g-1 e 76,9 J.g-1 para a formulação com 0,25% de goma guar e 0,25% de goma xantana na massa não congelada e após 28 dias de armazenamento congelado), indicando uma interação entre as gomas na capacidade de ligar água ao longo do tempo de congelamento. Porém, apesar do tempo de congelamento ter reduzido a entalpia de fusão, o processo de congelamento foi o principal fator na queda da taxa de fermentação e da produção de gás pelas leveduras independentemente do tempo de armazenamento congelado. / The knowledge of thermophysical properties is important to model and optimize equipment design for frozen food processes. In this work, the thermophysical bread dough properties, such as, thermal conductivity, thermal diffusivity and specific heat were experimentally determined during freezing process, due to their influence on the kinetics process, and therefore on bread quality. The results showed that some properties varied according to the initial water content and mainly due to temperature changes. The average value of initial freezing temperature found by water activity (aw = 0.950) explains the deviations between experimental data and available models in the literature based on Raoults law, which is related to the ice mass fraction. The combined use of guar and xanthan gums reduced the fusion enthalpy along frozen storage time (87.4 J.g-1 and 81.2 J.g-1 for formulation without gum, non-frozen and after 28 frozen storage days; 84.4 J.g-1 and 76.9 J.g-1 for formulation with 0.25 % of guar gum and 0.25 % of xanthan gum in non-frozen and after 28 frozen storage days). It indicated the interaction between gums and their ability to hold water along frozen storage. Despite frozen storage reduced the fusion enthalpy, the freezing process itself was the main factor in the decrease in proofing rate and gas production by yeast cells.

O processo de microfiltração tangencial com membranas tubulares inorgânicas e tubos microporosos, respectivamente de origem importada e nacional, foi investigado tendo-se como objeto de separação as misturas macromoleculares preparadas com os agentes polissacarídeos gomas Xantana e Guar em suspensão aquosa. São evidenciados neste processo os efeitos de sinergia compreendidos nas misturas elaboradas puras e em diferentes proporções, na concentração final de 1000 ppm. A investigação experimental acompanha o comportamento reológico de cada mistura ao longo do processo e os resultados foram investigados a partir de propriedades físico-químicas relevantes como: concentração de carbono orgânico total (Total Organic Carbon - TOC) e análise de absorbância no espectômetro de infravermelho. Resultados de TOC indicaram que em apenas um meio filtrante tubular microporoso (C1T+), o desempenho do processo na retenção dos polissacarídeos foi acima de 90%, em relação ao processo com a membrana comercial importada cuja retenção de TOC foi da ordem de 80%. De acordo com as análises de absorbância, conclui-se que as membranas com tamanho do poro nominal de 0,2 \'mü\'m e 0,4 \'mü\'m tiveram uma retenção mais eficiente do que os tubos microporosos em estudo. A temperatura foi um parâmetro significativo, pois a retenção, na maioria dos casos, foi maior na temperatura de 25ºC, independente da pressão e da velocidade média. Na análise dos procedimentos envolvendo cada mistura, foi constatada a boa sinergia entre as gomas, sem modificação de estrutura (formação de gel) ou fenômenos de superfície que impedissem o processo de microfiltração. A vazão transmembrana das misturas ficou limitada entre os máximos valores para mistura pura de Xantana e mínimos para Guar. Todas as misturas apresentaram comportamento pseudoplástico, sem mudanças na reologia, reforçando a adequada sinergia quanto a este aspecto. / The present dissertation reports cross-flow microfiltration with national and imported inorganic tubular membranes and microporous tubes. The object of separation is the macromolecular mixtures prepared with polysaccharide agents Xanthan and Guar gum in aqueous solution. The process shows the synergism effects in pure and different mixture proportions, with 1000 ppm final concentration. The experiments established the rheologic behaviour of each mixture along the process and significant physical and chemical properties, such as Total Organic Carbon concentration (TOC) and absorbency analysis in infrared spectrometer were analyzed. TOC retention shows that only one microporous tubular filtering medium (C1T+) had better performance (retention 90%) than the imported commercial membrane (retention about 80%). Absorbency analysis show a better retention efficiency of membranes with pore size of 0,2 \'mü\'m and 0,4 \'mü\'m than microporous tube. The temperature was a significant parameter, as the better retention was obtained at 25ºC, independently of pressure and mean velocity. There is good synergism between Xanthan and Guar gums without structure modifications or surface phenomena that would impede the microfiltration process. The transmembrane flux of proportional mixtures has been limited between maximum values of pure Xanthan and minimum values of pure Guar mixtures. All mixtures have pseudoplastic behaviour, without changes in rheology, intensifying the good synergism.

Le traitement de l’asthme concerne une large population et fait appel très majoritairement à une administration par voie pulmonaire. Cette voie présente certains inconvénients qui pourraient être palliés par le recours à la voie buccale comme envisagé dans cette étude, avec une amélioration attendue de la compliance et de la biodisponibilité. Aussi ce travail a eu pour objectif de développer et caractériser une formulation mucoadhésive thermogélifiante à base de salbutamol. Au regard des contraintes liées à la voie buccale et à la prise en charge du traitement de l’asthme aigu, les principales propriétés pharmacotechniques attendues pour optimiser la biodisponibilité de cette formulation ont été : (i) une gélification optimale autour de 30°C après pulvérisation pour faciliter notamment l’administration ; (ii) des propriétés mécaniques et mucoadhésives importantes pour assurer un maintien de la forme au site d’absorption ; (iii) une cinétique de libération compatible avec le traitement de la phase aigüe de la pathologie. Le choix des excipients a été défini afin d’avoir la plus grande innocuité de la formulation finale. Les travaux expérimentaux ont mis en évidence l’intérêt de certaines techniques innovantes pour la caractérisation de ce type de formulation comme notamment l’étude de libération à l’aide de l’appareil de dissolution à flux continu, la détermination de la cytotoxicité par microscopie holographique digitale et l’évaluation de la mucoadhésion in vitro et in vivo par imagerie. Les résultats ont aussi permis de proposer des modèles mathématiques pour l’interprétation des mécanismes de libération du salbutamol et quantifier l’importance des phénomènes de diffusion et d’érosion. Les conclusions de cette étude sont favorables à la poursuite du développement en vue d’une commercialisation. / The treatment of asthma concerns a large population and generally necessitates an administration by the pulmonary route. This route has some drawbacks which could be overcome by the buccal route, like considered in this study expecting an improvement of the compliance and the bioavailability. The aim of this work was to develop and characterize a thermogelling mucoadhesive formulation containing salbutamol sulfate. The main properties of the formulation were: (i) thermogelation around 30°C to facilitate the administration by spray; (ii) strong mechanical properties and high mucoadhesive strength to maintain the formulation in situ; (iii) drug release kinetics adapted to the treatment. The excipients were selected with regard to the final formulation safety. The experimental work emphasized the great interest of certain techniques in the characterization of this kind of formulation, for example the drug release study using flow through apparatus, the cytotoxicity study using digital holographic microscopy and also the mucoadhesion study by in vivo imaging. The use of mathematical models provided a relevant understanding of drug release mechanisms. The conclusion of this study is favorable to a further development of the project for a future marketing.

A qualidade global da massa de pão congelada por um longo período é um desafio para indústria de panificação. O uso de diferentes técnicas pode ajudar a explicar os danos sofridos à massa de pão durante o congelamento e armazenamento congelado. A presença de água na forma de cristais de gelo foi vista como a principal causa de defeitos à estrutura da massa. Gomas guar e xantana foram incorporadas às massas para contornar os danos causados pelo congelamento. Das análises térmicas conduzidas em calorímetro de varredura diferencial foi possível quantificar a quantidade de gelo presente na massa. A adição de (0,125 a 0,250) g/100g de goma guar e de (0,214 e 0,250) g/100g de goma xantana diminuíram os valores de entalpia na massa ao longo do armazenamento congelado. A fração de gelo foi menor e mais estável nas massas contendo (0,125 e 0,250) g/100g de goma guar ou xantana. O valor da atividade de água diminuiu nas massas contendo goma guar e com níveis mais altos de goma xantana, após o ciclo de congelamento e descongelamento e 170 dias de armazenamento. Alterações na estrutura das massas foram medidas e visualizadas pela análise de textura e por microscopia eletrônica de varredura (MEV). Adição de goma xantana e principalmente de goma guar às massas aumentaram a resistência à extensão após 170 dias de armazenamento congelado. A extensibilidade não foi influenciada pela adição de gomas e manteve estabilidade nos períodos de armazenamento estudados. A MEV ajudou a explicar os danos causados à rede de glúten pelos cristais de gelo ao longo do armazenamento congelado. A massa sem gomas apareceu com pequenos danos na rede de glúten com 21 dias de armazenamento e estes danos aumentaram progressivamente por até 170 dias, mostrando um glúten menos contínuo, mais rompido e separado dos grânulos de amido. As massas contendo gomas minimizaram, mas não evitaram os danos causados ao longo do armazenamento congelado. / The global quality of the frozen bread dough for long periods of frozen storage is the challenge to bakery industry. The use of different techniques could help to explain the damages caused in the frozen dough during the freezing and along frozen storage time. The presence of water as ice crystals was the main cause of damage on the dough structure. In order to minimize the freezing damages, guar and xanthan gums were incorporated in the dough. From thermal analysis by DSC technique, the amount of ice present in the dough was determined. The addition of (0.125 to 0.250) g/100g guar gum and (0.214 and 0.250) g/100g xanthan gum presented lower values of fusion enthalpy. The addition of (0.125 and 0.250) g/100g of guar gum decreased or stabilized the frozen water content, suggesting minimal damage on the dough structure along frozen storage time. The water activity in the dough samples with guar gum and higher quantities of xanthan gum decreased after the freezing-thawed cycle and after a period of frozen storage of 170 days. The incorporation of xanthan gum and mainly the incorporation of guar gum increased the maximum resistance of the dough after 170 days. The extensibility was not affected by addition of gums along frozen storage time. The MEV technical helped to explain the damaged dough structure caused by ice crystals along frozen storage time. Dough samples without gums presented structure damage only after 21 days and increased after 170 days, resulting in less continuous gluten, more disrupted and separated from starch granules. The doughs with gums suffered less damage in the gluten matrix, but did not avoid the problems caused by frozen storage.