[pt] Muitas indústrias, como as de petróleo, cosméticos e farmacêuticos, buscam estabilizar emulsões de forma efetiva e com menor custo. O uso de partículas sólidas como agentes emulsificantes (emulsões Pickering) tem apresentado grandes benefícios, como custo e estabilidade das emulsões, quando comparados aos surfactantes, que são utilizados na emulsão clássica. A eficácia de uma determinada partícula na estabilização de uma emulsão depende das suas propriedades e da sua interação com as fases oleosa e aquosa da emulsão. Essas partículas sólidas adsorvem-se na interface óleo-água criando uma fina camada entre as fases, evitando a coalescência das gotas. Uma forma de estudar a estabilidade de emulsões Pickering é analisar o experimento de coalescência de duas interfaces óleo-água que são forçadas uma contra a outra. A metodologia deste trabalho baseou-se em medições do tempo de coalescência de uma gota de óleo, presente em uma dispersão aquosa de nanopartículas, quando a mesma é forçada contra uma interface óleoágua. Para a correta visualização e registro do momento da coalescência da gota utilizou-se uma câmera de alta velocidade (Photron FastCam SA3). As nanopartículas utilizadas foram: Laponita RD, dióxido de titânio HAc e Aerosil R972. Observou-se tempos de coalescência maiores para testes com dispersões aquosas de Laponita RD 1,0 porcento (m/m) e de Aerosil R972 0,0024 porcento (m/m) do que para testes com água pura (Milli-Q). / [en] Several industries, such as oil and gas, cosmetics, and pharmaceutical, seek to stabilize emulsions more effectively and at a lower cost. As compared to surfactants, which are used in classic emulsions, the use of solid particles as emulsifying agents (Pickering emulsions) has presented great benefits, including lower costs and better emulsion stability. A particle s effectiveness on stabilizing an emulsion is related to its properties, as well as its interaction with the oil and water phases of the emulsion. These solid particles adsorb at the oil-water interface, creating a thin layer between the phases, and thus avoiding the coalescence of the droplets. One method to study the stability of Pickering emulsions is to analyze the coalescence experiment of two oil-water interfaces that are forced against each other. The methodology of this work was based on measurements of the coalescence time of an oil droplet in an aqueous dispersion of nanoparticles, when it is forced against an oil-water interface. A high speed camera (Photron FastCam SA3) was used for the proper visualization and recording of the moment of drop coalescence. The three types of nanoparticles used were: Laponite RD, titanium dioxide HAc, and Aerosil R972. Longer coalescence times were observed for tests with aqueous dispersions of Laponite RD 1.0 percent (w/w) and Aerosil R972 0.0024 percent (w/w) versus tests with plain water (Milli-Q).

In recent years, water-in-oil Pickering emulsions have been introduced as promising reaction systems for multiphase enzyme catalysis, in particular lipase-catalyzed esterification and transesterification. Here, we for the first time gained insight into the effects that the presence of the proteins exert on the fineness and stability of the emulsion system and thus, the catalytic performance. We demonstrated a distinct, concentration-and enzyme-dependent decrease of droplet sizes in the dispersed phase, accompanied by decreasing stability against coalescence. This was due to a probably quantitative adsorption of lipases at the interphase intercalating the solid particles. Destabilization was reduced slightly at increased particle content and increased volume portion of the dispersed phase, respectively. However, the low tolerable lipase concentrations in the reaction system considerably limited its productivity. Thus, our study points at the enzyme content, or rather enzyme location, in Pickering emulsions being the crucial parameter for optimizing catalytic performance.

Des émulsions particulièrement stables peuvent être formulées à l’aide de particules colloïdales (émulsions dites de Pickering). L’objectif de cette étude est d’accéder à la compréhension des mécanismes de stabilisation des interfaces, ainsi que du lien entre propriétés interfaciales et propriétés macroscopiques des émulsions. Dans ce cadre, la stratégie adoptée repose sur l’utilisation de particules colloïdales dont les caractéristiques peuvent être variées continûment à la fois en amont par la chimie de synthèse (variation de la mouillabilité, de la déformabilité) et in situ par un stimulus (pH, sel, température...). De plus,les émulsions stabilisées par de telles particules deviennent, elles aussi, sensibles aux stimuli et la déstabilisation des émulsions peut être déclenchée à la demande. Les mécanismes d’adsorption, les interactions entre particules aux interfaces et les propriétés résultantes des émulsions sont étudiés. L’établissement de concepts généraux régissant la stabilisation/déstabilisation des émulsions permet d’en contrôler, via la formulation ou le procédé (température, cisaillement), les propriétés d’usage. Enfin les émulsions stabilisées par des particules colloïdales peuvent être utilisées en tant que précurseurs dans la formulation de matériaux plus complexes : ceci est illustré par l’élaboration de capsules à libération thermostimulée / Highly stable emulsions can be formulated using colloidal particles as stabilizers (so-calledPickering emulsions). This study aims at understanding the interfacial stabilizationmechanisms as well as the links between the interfacial properties and the macroscopicproperties of emulsions. In this context, our strategy consists in using colloidal particles forwhich characteristics can be continuously tuned either during the synthesis (variation of theparticles’ wettability or deformability) or in situ by using a stimulus (pH, salt, temperature…).Emulsions stabilized by such particles are stimuli responsive and their destabilization can betriggered on demand. We study and report the mechanisms of particle adsorption, theinteractions between particles anchored at interfaces and the resulting properties of emulsions.Such study allows us to draw general concepts governing the emulsionsstabilization/destabilization and to control their end-use properties via formulation oremulsification process (temperature, shear). Colloidal particle stabilized-emulsions can beused as templates to synthesize more complex materials as illustrated by the elaboration ofcapsules allowing a thermally controlled delivery of their content.

L’objectif de cette étude est de valoriser des coproduits végétaux tout en proposant une alternative biosourcée, économique et performante aux tensioactifs classiques. Des émulsions de type huile-dans-eau sont fabriquées à partir de poudres végétales finement broyées comme seul matériel tensioactif. Les systèmes dispersés qui en résultent, stabilisés par des particules solides, sont des émulsions dites de Pickering. La première partie de ce manuscrit décrit l’influence du procédé d’émulsification (rotorstator en régime turbulent, ultrasons et homogénéisation haute pression) et des paramètres de formulation sur les propriétés d’émulsions stabilisées par de la poudre de cacao. Le rôle des différentes fractions de la poudre est déterminé et le phénomène de coalescence limitée propre aux émulsions de Pickering est étudié. Nous mettons en évidence une évolution structurale des particules (« dépliement ») sous l’effet du cisaillement appliqué lors de l’émulsification, permettant d’augmenter leur performance en tant qu’agents stabilisants. L’influence de la nature végétale est explorée en élargissant l’étude à des poudres de compositions différentes issues de tourteaux de colza et de lupin. La stabilité de ces émulsions face à l’élimination de la phase continue est ensuite évaluée au regard de la technique de séchage, par lyophilisation et atomisation. Des émulsions sèches riches en huile et redispersables dans l’eau sont ainsi obtenues. Enfin, le pouvoir antioxydant des poudres végétales avant et après séchage des émulsions est caractérisé. / This study aimed at valorizing vegetal byproducts while offering a bio-sourced, cheap and efficient alternative to conventional surfactants. Oil-in-water emulsions were obtained from finely ground plant powders as the only surfactant material. The resulting dispersed systems, stabilized by solid particles, are so-called Pickering emulsions. The first part of this manuscript describes the influence of the emulsification process (rotor-stator in turbulent regime, sonication and high-pressure homogenization) and of the formulation parameters on the properties of emulsions stabilized by cocoa powder. The role of the different fractions of the powder was determined and a phenomenon characteristic of Pickering emulsions, namely limited coalescence, was identified. We evidenced a structural evolution of the particles ("unwrapping") under the effect of the shear applied during the emulsification process, allowing to increase their performance as stabilizing agents. The influence of the vegetal origin was explored by extending the study to powders deriving from rapeseed and lupin oilcakes. The stability of these emulsions with respect to the elimination of the continuous phase was evaluated using 2 drying techniques, freeze-drying and spray-drying. Dry emulsions rich in oil and redispersable in water were obtained. Finally, the antioxidant properties of vegetable powders before and after the drying process were characterized.

Submitted by Angela Maria de Oliveira (amolivei@uepg.br) on 2019-02-26T11:28:38Z No. of bitstreams: 2 license_rdf: 811 bytes, checksum: e39d27027a6cc9cb039ad269a5db8e34 (MD5) Taiana Huslia Gomes Daniel.pdf: 2854921 bytes, checksum: 558ae7bad090562fb907f55b5c80bd02 (MD5) / Made available in DSpace on 2019-02-26T11:28:38Z (GMT). No. of bitstreams: 2 license_rdf: 811 bytes, checksum: e39d27027a6cc9cb039ad269a5db8e34 (MD5) Taiana Huslia Gomes Daniel.pdf: 2854921 bytes, checksum: 558ae7bad090562fb907f55b5c80bd02 (MD5) Previous issue date: 2018-11-29 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Os nanocristais de amido são partículas de tamanho nanométrico que vêm recebendo atenção por parte dos pesquisadores pois são abundantes, biodegradáveis, não tóxicos e apresentam relativo baixo custo. Essas nanopartículas cristalinas podem ser utilizadas como estabilizantes de emulsões Pickering, sistemas onde o tamanho das partículas é fator primordial para a estabilidade. Entretanto, a forte tendência dessas partículas em formar agregados de tamanho micrométrico limita a aplicação tecnológica. Desta forma, a oxidação química com hipoclorito de sódio pode ser uma alternativa para minimizar esse comportamento indesejado. Os amidos de mandioca e de milho são abundantes e baratos, enquanto o amido de feijão, apesar de ter características tecnológicas interessantes e promissoras, ainda não é extraído comercialmente. O objetivo deste trabalho foi caracterizar nanocristais produzidos a partir de amidos de mandioca, de feijão e de milho, proceder a oxidação dos nanocristais e utilizá-los como estabilizadores de emulsões Pickering. Os nanocristais foram obtidos por hidrólise com ácido sulfúrico e oxidados com hipoclorito de sódio. As emulsões foram preparadas utilizando-se óleo de soja e água. O amido de feijão foi o mais resistente à hidrólise, seguido dos amidos de milho e de mandioca. Em ambas as fontes botânicas a hidrólise ácida diminuiu consideravelmente o conteúdo de amilose nas nanopartículas. A oxidação aumentou o potencial zeta de todos os nanocristais, além de diminuir a polidispersividade. Por meio da espectroscopia na região do infravermelho médio detectou-se um pico a 1735 cm-1 característico dos grupos carboxilas livres (forma ácida – COOH), típico de amidos oxidados. Os amidos de mandioca e de milho apresentaram padrão cristalino tipo A, assim como seus nanocristais. Contudo, foi observado no feijão padrão cristalino tipo C - A, que permaneceu no nanocristal; por meio da oxidação, entretanto, o padrão foi alterado para o tipo A. Após a hidrólise, a cristalinidade relativa aumentou para todas as amostras, porém com a oxidação a mesma diminuiu, exceto para o amido de feijão que resultou em efeito contrário. As amostras oxidadas apresentaram maior estabilidade coloidal, quando comparadas com as não oxidadas. Os nanocristais não apresentaram pico endotérmico detectável pela análise de DSC (Calorimetria Exploratória Diferencial). Na análise de microscopia os nanocristais exibiram formas redondas ou ovais, independentemente da origem do amido, mesmo após terem sido submetidos à oxidação. Em geral a oxidação dos nanocristais melhorou o índice de emulsão das amostras, independente da fonte botânica de origem, além disso o índice foi maior para as amostras com maior proporção de óleo em relação com as com maior fração de água. Contudo o aumento da fase oleosa aumentou o diâmetro médio das gotículas. O valor de PDI variou de 1,6, para emulsão com proporções de água e óleo 1:1 estabilizada com 5% nanocristal de mandioca oxidado, até 3,5, para emulsão com proporção de água e óleo 1:3 estabilizada com 1% de nanocristal de feijão oxidado. / The nanocrystals of starch are particles of nanometric size that have been studied, since they are abundant, biodegradable, non-toxic and with relative low cost. However, the tendency to form micrometricsize aggregates limits the technological application; therefore, chemical oxidation with sodium hypochlorite may be an alternative for limiting such unwanted behavior. These nanocrystals can be used as stabilizers for Pickering emulsions, systems where particle size is a prime factor for stability. Cassava and maize starches are abundant and cheap, while bean starch, although an interesting and promising technological product, is not yet commercially available. The present work had as objective the production and characterization of nanocrystals from cassava, bean and corn starches, following chemical oxidation of the nanocrystals and using them as emulsion stabilizers. The nanocrystals were obtained by hydrolysis with sulfuric acid and oxidized with sodium hypochlorite. The emulsions were prepared using soybean oil and water. Bean starch was less susceptible to hydrolysis, followed by maize and cassava starches. In both botanical sources the acid hydrolysis greatly reduced the amylose content in the nanoparticles. Oxidation increased the zeta potential of all the nanocrystals, besides the value of polydispersity decreased. A peak at 1,735 cm-1 was detected by means of mid-infrared spectroscopy, which is characteristic of the free carboxyl group (acid form - COOH), expected on oxidized starches. Cassava and corn starches have Atype crystallinity pattern, as their nanocrystals. For bean starch, the original C-Atype crystallinity pattern remained for the non-oxidized nanocrystals but changed for A-type after oxidation. After hydrolysis, the relative crystallinity increased for nanocrystals, but decreased after oxidation. The exception was for bean starch that resulted in oxidized nanocrystals with higher relative crystallinity. Oxidized samples are considered as colloidal when compared to non-oxidized ones. Nanocrystals did not show detectable endothermic peak on DSC (differential scanning calorimetry) analysis. The microscopic analysis of the nanocrystals showed round or oval particles, independently of the botanical source and of oxidation treatment. In general, the oxidation of nanocrystals improved their emulsification index. The emulsification index was higher for the emulsions with larger amounts of oil, even though the average diameter of the droplets increased in this situation. The polydispersity index ranged from 1.6 for 1: 1 (water to oil ratio), stabilized with 5% oxidized cassava nanocrystal, up to 3.5 for 1: 3 (water to oil ratio), stabilized with 1% of oxidized bean nanocrystal.

Die vorliegende Arbeit beschreibt Herstellungsmöglichkeiten für sogenannte Saturn-Partikel. Es handelt sich dabei um Partikel, die auf ihrer Oberfläche drei Bereiche mit unterschiedlichen Eigenschaften aufweisen. Zwei Kappen mit gleichen Eigenschaften sind durch einen Gürtel getrennt, der sich stark von den Kappen unterscheidet. Im Speziellen geht es hier um die unterschiedliche Benetzbarkeit der Bereiche. Die Herstellung von Saturn-Partikeln mit einem hohen Benetzungskontrast wurde auf zwei verschiedenen Wegen realisiert. Als Ausgangspunkt dienten Mikroglaskugeln, die zunächst zur Hydrophobierung ihrer Oberfläche mit einem Silan behandelt wurden. Eine Art der Saturn-Partikel wurde durch das Ätzen eines Gürtels rund um die Partikel mit Flusssäure in einer im Rahmen dieser Arbeit entwickelten Spülzelle erzeugt. Auf diese Weise konnten Partikel mit zwei hydrophoben Kappen und einem hydrophilen Gürtel erhalten werden. Eine weitere Art dieser Partikel wurde durch das Abschleifen der Partikelkappen nach vorheriger Einbettung in Polymerfilme erhalten, wodurch die hydrophobe Beschichtung abgetragen und das ursprünglich hydrophile Glas freigelegt wurde. Die so erhaltenen Partikel wiesen zwei parallele, hydrophile Bereiche auf, die durch einen hydrophoben Gürtel voneinander getrennt waren. Es wird gezeigt, dass Saturn-Partikel in Systemen mit Wasser und Öl beim Mischen von unterschiedlichen Anteilen der drei Phasen durch Selbstorganisationsprozesse verschiedene Strukturen wie Ketten oder Schichten ausbilden können. Des Weiteren sind sie in der Lage in einem System mit Wasser und Luft besondere Schäume auszubilden, die eine sehr hohe Stabilität aufweisen. Die Partikel stabilisieren darin Flüssigkeitsfilme zwischen den Luftblasen, wobei der hydrophile Gürtel im Wasserfilm und die hydrophoben Kappen in der Luft liegen.

L’encapsulation est une technique employée couramment par le milieu industriel, notamment dans le domaine du médical, de la parfumerie ou de la cosmétique. Afin de répondre aux attentes et de proposer des capsules modulables pour tous types d’applications, des capsules de type coeur-écorce ont été élaborées au cours de cette thèse. Elles sont obtenues à partir d’émulsion dont le coeur huileux est enrobé par une coque de silice, via la minéralisation de l’interface eau-huile. Les émulsions de Pickering, stabilisées par des particules colloïdales, sont particulièrement stables et intéressantes pour cette étude. Le but de cette thèse est de comprendre, dans un premier temps, les mécanismes fondamentaux impliqués dans le processus de fabrication. Cela a permis d’élaborer, par la suite, des matériaux hybrides complexes à différentes échelles, du micrométrique au nanométrique,mais également d’établir les mécanismes de libération par un stimulus externe. Enfin, une encapsulation maîtrisée permet d’allier stabilité au stockage et destruction rapide ou contrôlée à l’utilisation. Ainsi, par diverses méthodes définies dès la formulation de l’émulsion initiale, le contenu huileux des capsules peut être libéré de manière provoquée par une action mécanique ou par l’augmentation de la température (macroscopique ou local par hyperthermie magnétique). / Encapsulation is a technique used in the industry, in particular in the field of medical,perfumery or cosmetics. In order to meet the expectations and propose adaptable capsules for all types of applications, core-shell capsules type were developed during this thesis.There were based on emulsions science with an oily core coated by a silica shell,synthetized by sol-gel chemistry at the oil-water interface. Pickering emulsions, which are emulsions stabilized by colloidal particles, are particularly stable and interesting for this study. The aim of this thesis is to understand, at first, the fundamental mechanisms involved in the manufacturing process. This made it possible to develop complex hybrid materials at different scales, from micrometric to nanometric, but also to establish the releasing mechanisms by an external stimulus. Thanks to a controlled encapsulation, it is possible to combine stability (storage) and rapid or controlled destruction when used. Thus, by various method, defined from the formulation of the initial emulsion, the releasing of the oily contentcan be caused by mechanical action or by an temperature increased (macroscopically orlocally by magnetic hyperthermia).

Die vorliegende Arbeit beschreibt Herstellungsmöglichkeiten für sogenannte Saturn-Partikel. Es handelt sich dabei um Partikel, die auf ihrer Oberfläche drei Bereiche mit unterschiedlichen Eigenschaften aufweisen. Zwei Kappen mit gleichen Eigenschaften sind durch einen Gürtel getrennt, der sich stark von den Kappen unterscheidet. Im Speziellen geht es hier um die unterschiedliche Benetzbarkeit der Bereiche. Die Herstellung von Saturn-Partikeln mit einem hohen Benetzungskontrast wurde auf zwei verschiedenen Wegen realisiert. Als Ausgangspunkt dienten Mikroglaskugeln, die zunächst zur Hydrophobierung ihrer Oberfläche mit einem Silan behandelt wurden. Eine Art der Saturn-Partikel wurde durch das Ätzen eines Gürtels rund um die Partikel mit Flusssäure in einer im Rahmen dieser Arbeit entwickelten Spülzelle erzeugt. Auf diese Weise konnten Partikel mit zwei hydrophoben Kappen und einem hydrophilen Gürtel erhalten werden. Eine weitere Art dieser Partikel wurde durch das Abschleifen der Partikelkappen nach vorheriger Einbettung in Polymerfilme erhalten, wodurch die hydrophobe Beschichtung abgetragen und das ursprünglich hydrophile Glas freigelegt wurde. Die so erhaltenen Partikel wiesen zwei parallele, hydrophile Bereiche auf, die durch einen hydrophoben Gürtel voneinander getrennt waren. Es wird gezeigt, dass Saturn-Partikel in Systemen mit Wasser und Öl beim Mischen von unterschiedlichen Anteilen der drei Phasen durch Selbstorganisationsprozesse verschiedene Strukturen wie Ketten oder Schichten ausbilden können. Des Weiteren sind sie in der Lage in einem System mit Wasser und Luft besondere Schäume auszubilden, die eine sehr hohe Stabilität aufweisen. Die Partikel stabilisieren darin Flüssigkeitsfilme zwischen den Luftblasen, wobei der hydrophile Gürtel im Wasserfilm und die hydrophoben Kappen in der Luft liegen.