Emulsions form a major part of processed food formulations, either being the end products in themselves or as parts of a more complex food system. For the past few decades, colloid scientists have focussed mainly on the effects of processing conditions (e.g. heat, high pressure, and shear) on the physicochemical properties of emulsions (e.g. viscosity, droplet size distribution and phase stability). However, the information about the behaviour of food structures post consumption is very limited. Fundamental knowledge of how the food structures behave in the mouth is critical, as these oral interactions of food components influence the common sensorial perceptions (e.g. creaminess, smoothness) and the release of fat-soluble flavours. Initial studies also suggest that the breakdown of emulsions in the gastrointestinal tract and the generated interfacial structures impact lipid digestion, which can consequently influence post-prandial metabolic responses. This area of research needs to be intensively investigated before the knowledge can be applied to rational design of healthier food structures that could modulate the rate of lipid metabolism, bioavailability of nutrients, and also help in providing targeted delivery of flavour molecules and/or bioactive components. Hence, the objective of this research was to gain understanding of how emulsions behave during their passage through the gastrointestinal tract. In vitro digestion models that mimic the physicochemical processes and biological conditions in the mouth and gastrointestinal tract were successfully employed. Behaviour of model protein-stabilized emulsions (both positively charged (lactoferrin) as well as negatively charged [β-lactoglobulin (β-lg)] oil-in-water emulsions) at each step of simulated physiological processing (using model oral, gastric and duodenal fluids individually) were investigated. In simulated mouth conditions, oil-in-water emulsions stabilized by lactoferrin or β-lg at the interfacial layers were mixed with artificial saliva at neutral pH that contained a range of mucin concentrations and salts. The β-lg emulsions did not interact with the artificial saliva due to the dominant repulsion between mutually opposite charges of anionic mucin and anionic β-lg interfacial layer at neutral pH. However, β-lg emulsions underwent some depletion flocculation on addition of higher concentrations of mucin due to the presence of unadsorbed mucin molecules in the continuous phase. In contrast, positively charged lactoferrin emulsions showed considerable salt-induced aggregation in the presence of salts (from the saliva) alone. Furthermore, lactoferrin emulsions underwent bridging flocculation because of electrostatic binding of anionic mucin to the positively charged lactoferrin-stabilized emulsion droplets. In acidic pH conditions (pH 1.2) of the simulated gastric fluid (SGF), both protein-stabilized emulsions were positively charged. Addition of pepsin resulted in extensive droplet flocculation in both emulsions with a greater extent of droplet instability in lactoferrin emulsions. Coalescence of the droplets was observed as a result of peptic hydrolysis of the interfacial protein layers. Conditions such as ionic strength, pH and exposure to mucin were shown to significantly influence the rate of hydrolysis of β-lg-stabilized emulsion by pepsin. Addition of simulated intestinal fluid (SIF) containing physiological concentrations of bile salts to the emulsions showed competitive interfacial displacement of β-lg by bile salts. In the case of lactoferrin-stabilized emulsion droplets, there was considerable aggregation in the presence of intestinal electrolytes alone (without added bile salts) at pH 7.5. Binding of anionic bile salts to cationic interfacial lactoferrin layer resulted in re-stabilization of salt-aggregated lactoferrin emulsions. On mixing with physiological concentrations of pancreatin (mixture of pancreatic lipase, amylase and protease), significant degree of coalescence and fatty acid release occurred for both the emulsions. This was attributed to the interfacial proteolysis by trypsin (proteolytic fractions of pancreatin) resulting in interfacial film rupturing. Exchange of initial interfacial materials by bile salts and trypsin-induced film breakage enhanced the potential for lipolytic fractions of pancreatin to act on the hydrophobic lipid core. The lipid digestion products (free fatty acids and mono and/or diglycerides) generated at the droplet surface further removed the residual intact protein layers from the interface by competitive displacement mechanisms. The sequential treatment of the cationic and anionic emulsions with artificial saliva, SGF and SIF, respectively, was determined to understand the impact of initial protein type during complete physiological processing from mouth to intestine. Broadly, both the protein-stabilized emulsions underwent charge reversals, extensive droplet flocculation, and significant coalescence as they passed through various stages of the in vitro digestion conditions. Except in the simulated mouth environment, the initial charge of the emulsifiers had relatively limited influence on droplet behaviour during the simulated digestion. The results contribute to the knowledge of how structure and charge of the emulsified lipid droplets impact digestion at various stages of physiology. This information might have important consequences for developing suitable microstructures that allow controlled breakdown of droplets in the mouth and predictable release of lipids in the gastrointestinal tract.

Thesis (Ph.D.)--University of Melbourne, Dept. of Mathematics and Statistics, 2007. / Typescript. Includes bibliographical references (leaves 143-151).

Thesis (Ph. D.)--University of Washington, 2002. / Vita. Includes bibliographical references (p. 71-76).

Thesis (Ph. D.)--University of Texas at Austin, 2000. / Vita. Includes bibliographical references (leaves 248-269). Available also in a digital version from Dissertation Abstracts.

Thesis (Ph. D.)--Florida State University, 2005. / Advisor: Oliver Steinbock, Florida State University, College of Arts and Sciences, Dept. of Chemistry and Biochemistry. Title and description from dissertation home page (viewed Jan. 24, 2006). Document formatted into pages; contains xii, 123 pages. Includes bibliographical references.

Thesis (Ph.D.)--University of Delaware, 2007. / Principal faculty advisor: Kausik Sarkar, Dept. of Mechanical Engineering. Includes bibliographical references.

abstract: Alkali treated aluminosilicate (geopolymer) was functionalized by surfactant to increase the hydrophobicity for making Pickering emulsion for the first part of this work. In the first part of this study, alkali treated metakaolin was functionalized with cetyltrimethylammonium bromide ((C16H33)N(CH3)3Br, CTAB). The electrostatic interaction between this quaternary ammonium and the surface of the aluminosilicate which has negative charge has taken place. The particles then were used to prepare Pickering emulsion. The resulting stable dispersions, obtained very fast at very simple conditions with low ratio of aluminosilicate to liquid phase. In the second part, the interaction between geopolymer and glycerol was studied to see the covalent grafting of the geopolymer for making geopolymer composite. The composite material would be the basis material to be used as support catalyst, thin coating reagent and flame retardant material and so on, Variety of techniques, Thermogravimetric (TGA), Particle-induced X-ray emission (PIXE), FTIR, Solid state NMR, Powder X-ray diffraction (PXRD), BET surface area, Elemental analysis (CHN), TEM, SEM and Optical microscopy were used to characterize the functionalized geopolymer. / Dissertation/Thesis / M.S. Chemistry 2012

[pt] Na produção de petróleo, durante a recuperação secundária, a injeção de água no reservatório de petróleo com o objetivo de deslocar o óleo até o poço produtor pode levar a um regime de escoamento bifásico onde ocorre a formação de emulsões. As emulsões são um problema para a indústria do petróleo porque produzem perda de carga nas linhas de produção e tornam difíceis os processos de separação óleo-água, gerando altos custos. Este fenômeno ainda não é bem entendido e não é exclusivo do que ocorre no meio poroso porque também está presente nas diferentes etapas da produção de petróleo. Este trabalho foi focado na formação de emulsões no meio poroso de um reservatório, considerando especialmente o escoamento bifásico na escala de poros. Assim foi utilizada uma junção de micro canais em T para descrever o que poderia acontecer na união de duas gargantas de poros em um reservatório de petróleo. Neste caso utilizamos a técnica de formação de gotas por fluxo cruzado estudada e desenvolvida, nas últimas décadas, na área de micro-fluídica. Através da injeção de dois líquidos imiscíveis nos canais que formam a junção, foi estabelecido um regime estável de formação de gotas. Para estudar a influência das diferentes variáveis do processo na formação de gotas, foram variadas as vazões dos líquidos injetados e suas propriedades, como viscosidades e tensão interfacial. Os resultados mostram que os diferentes regimes de escoamento e formação de gotas observados não são só uma função do número de capilaridade da fase contínua, como sugere a literatura para junções micro-fluídicas T de seção retangular. Nos experimentos desenvolvidos neste trabalho, nos quais a seção reta dos canais é oval e a fase contínua é a fase aquosa, as características da fase dispersa, como vazão e viscosidade, tiveram uma grande influência no processo de formação de gotas. / [en] In oil production, during secondary recovery, water injection into the reservoir to displace oil towards the production well generates different phenomena, among which is emulsion formation. Emulsions are a problem for the oil industry, because they change the pressure drop in production lines and hardens the process of separating oil-water, generating high operating costs. Emulsion formation in oil production is not yet well understood and it does not only occur in porous media, emulsion formation also occurs during different stages of oil production. This work was focused on the emulsion formation in porous media specifically considering the pore scale two phase flow. A T-junction microfluidic device was used as a model of the union of two pore throats in a porous media. We studied droplet formation in cross-flowing streams, a technique studied and developed in the past decade in the area of microfluidics technologies. Through the injection of two immiscible liquids in the channels of the device, we established a stable droplet formation regime. To study the influence of different variables that govern drop formation, we varied the flow rates of both immiscible phases and their properties, such as viscosity and interfacial tension. The results show that the different regimes observed are not only a function of capillary number, defined based on the continuous phase, as suggested in the literature for microfluidic T junctions with rectangular cross section. In our experiments the cross section of the channel had an elliptic shape and the continuous phase was aqueous, and the characteristics of the dispersed phase had a great influence in the process of drop formation.

[pt] Evidências experimentais demonstram o potencial da injeção de emulsões no aumento do fator de recuperação de óleo. O mecanismo responsável por esta melhor varredura do reservatório é a redução da mobilidade da água em regiões do reservatório já varridas por água. Esta redução pode ser associada ao bloqueio parcial de gargantas do meio poroso por gotas da fase dispersa da emulsão. A eficiência deste bloqueio parcial depende fortemente da geometria do poro, das características morfológicas e propriedades físicas da emulsão injetada. A utilização eficiente deste método de recuperação é limitada pela falta de entendimento fundamental de como emulsões escoam através de um meio poroso. Este trabalho tem como objetivo estudar o escoamento de emulsões através de gargantas de poros, que são modeladas fisicamente por micro- capilares com garganta nos experimentos desenvolvidos nesta pesquisa. Os resultados mostram como a permeabilidade varia com as propriedades e características morfológicas da emulsão e parâmetros geométricos do micro-capilar. Estes dados definem as propriedades necessárias de emulsões em função das características do reservatório para a obtenção do efeito de bloqueio parcial desejado e servem de entrada de dados para modelo de rede de capilares de escoamento de emulsões em meios porosos. / [en] Experimental evidences show the potential of emulsion injection in the improvement of oil recovery factor. The responsible mechanism for this better reservoir sweep is the water mobility reduction in regions already swept by water. This reduction can be associated with partial blockage of porous media throats by droplets of emulsion dispersed phase. The efficiency of this partial blockade strongly depends on pore geometry, morphological characteristics and physical properties of the injected emulsion. The efficient use of this recovery method is limited by the lack of fundamental understanding of how emulsions flow through a porous medium. This work aims to study the flow of emulsions through pores throats, which are physically modeled by constricted micro- capillaries in the experiments presented here. The results show how permeability varies with geometrical parameters of micro-capillaries, emulsion properties and morphological characteristics. These data define the necessary properties of emulsions according to the reservoir characteristics to obtain the desired blocking effect and serve as input data to capillaries network model of flow of emulsions in porous media.

[pt] A produção de óleo diminui e a produção de água aumenta com o passar do tempo na vida de um reservatório. A mistura de óleo e água é geralmente produzida na forma de uma emulsão. A formação da emulsão começa no escoamento bifásico no interior do reservatório e sua estrutura muda na medida em que os líquidos escoam através de tubulações, bombas e válvulas até as instalações de superfície. Durante a produção, as gotas maiores da fase dispersa quebram-se mudando a distribuição do tamanho das gotas. É importante conhecer a distribuição de tamanho de gota da fase dispersa da emulsão a fim de projetar as unidades de separação e prever as quedas de pressão ao longo do escoamento. O objetivo do presente trabalho é o estudo do processo de quebra de gotas em capilares retos e válvulas agulha a fim de prever o tamanho das gotas resultantes em função das condições de escoamento. O principal desafio é entender como os diferentes parâmetros operacionais de escoamento afetam o processo de quebra. Duas bancadas experimentais foram utilizadas para o estudo do processo. Na primeira, foi realizada uma análise paramétrica de formação de emulsões em um escoamento laminar através de capilares retos. Os experimentos foram realizados utilizando duas seringas conectadas através de um capilar. A emulsão óleo-emágua foi forçada a uma passagem de ida e vinda através do capilar. O diâmetro médio de gota e a superfície específica da fase dispersa foram obtidos em função da vazão de injeção, taxa de cisalhamento, tempo de residência e trabalho dissipado na parede do capilar. Como esperado, o diâmetro médio da fase dispersa diminui com o aumento do tempo de cisalhamento atingindo um valor assintótico e possui uma grande dependência com a taxa de cisalhamento na parede do capilar. Na segunda bancada, foi realizada uma análise paramétrica de um escoamento turbulento de emulsão óleo-em-água através de uma válvula agulha. Os experimentos foram realizados utilizando uma bomba helicoidal para controlar a vazão através da válvula. O diâmetro médio de gota e a superfície específica da fase dispersa a montante e a jusante da válvula foram obtidos em função da queda de pressão, vazão e taxa de dissipação de energia na válvula. O diâmetro médio da fase dispersa diminui e a superfície específica aumenta com o aumento da queda de pressão na válvula agulha até atingir um valor assintótico. / [en] Oil production decreases and water production increases as time goes by in the life of a hydrocarbon reservoir. The mixture of oil and water is usually produced as an emulsion. Emulsion formation starts in the two-phase flow inside the reservoir. The emulsion structure changes as it flows through pipes, pumps and valves up to the surface facilities. During all stages, large drops of the dispersed phase break up leading to smaller drops. It is important to know the droplet size distribution of the dispersed phase in order to design separation units and predict the pressure drop along the flow. The aim of the this work is to study the droplets break-up process that takes place in capillaries and in a needle valve in order to make predictions of the size of the resulting droplets that emerge from this process. The main challenge is to understand how the different operating flow parameters affect the break up process. In order to achieve this goal, two laboratory scale experimental set-ups have been used. In the first experiment, we conducted a parametric analysis of oil-water emulsion formation in laminar flow through straight capillaries. The experiments were carried out using two syringe pumps connected by a double-hubbed capillary pipe. The oil-water emulsion is forced back and forth through the pipe. The mean diameter and the specific surface area of the dispersed phase were obtained as a function of flow rate, shear rate, residence time and rate of energy dissipation at the capillary wall. As expected, keeping all other variables fixed, the dispersed phase mean diameter decreases with the shearing time, reaching an asymptotic value, which was a strong function of the shear rate at the capillary wall. Secondly, we conducted a parametric analysis of turbulent oil-in-water emulsion flow through a needle valve. The experiments were carried out using a helicoidal pump to control the flow rate through the needle valve. The mean diameter and the specific surface area of the dispersed phase upstream and downstream of the valve were obtained as a function of the pressure drop in the valve, flow rate, and rate energy dissipation of the flow. The dispersed phase mean diameter falls and the specific surface area rises with the pressure drop in the valve until reaching an asymptotic value.