Tesis por compendio / [ES] El objetivo de esta tesis doctoral ha sido el diseño y caracterización estructural de estructuras tipo gel basadas de polisacáridos extraídos de biomasa acuática con interés para aplicaciones relacionadas con la alimentación. Las propiedades de los polisacáridos extraídos de algas y plantas acuáticas son adecuadas para producir diferentes estructuras tipo gel basadas en la formación de redes reticuladas, como hidrogeles, aerogeles y emulsion-gels. En la primera parte de esta tesis se investigaron los diferentes mecanismos de gelificación de polisacáridos sulfatados, así como los parámetros que afectan a la estructura y las propiedades funcionales de los hidrogeles obtenidos. En base a los resultados, se evaluó la potencial aplicación de los hidrogeles y aerogeles de agar y k-carragenato para encapsular una proteína alimentaria modelo como la caseína, explorando así el efecto protector contra la hidrólisis enzimática tras digestiones gastrointestinales simuladas. En la segunda parte de esta tesis, se desarrollaron estructuras de aerogeles mediante la valorización de una fuente de biomasa residual infrautilizada, como es el Arundo donax. Con esta biomasa se generaron fracciones celulósicas con diferentes grados de purificación y extractos bioactivos solubles en agua, que posteriormente se utilizaron para producir aerogeles bioactivos híbridos. La estructura altamente porosa y la elevada capacidad de sorción de los aerogeles los convierten en excelentes candidatos para la sustitución de las almohadillas absorbentes para mantener la calidad de los productos cárnicos envasados. Los emulsion-gels son reconocidos por su gran potencial como ingredientes funcionales en la industria alimentaria como modificadores de textura y como sustitutos de grasas sólidas. Además, pueden utilizarse como vehículo para la liberación controlada de compuestos bioactivos liposolubles. Así, en la última parte de esta tesis, se investigó la naturaleza de las interacciones entre los componentes en las formulaciones de emulsion-gels basadas en polisacáridos y se relacionó con su estructura y comportamiento mecánico y reológico. Después de estudiar el mecanismo de gelificación de los emulsion-gels de carragenato, estos sistemas se adaptaron y utilizaron para dos diferentes aplicaciones relevantes para los sectores de alimentación y biomedicina. En primer lugar, se produjeron y evaluaron estructuras gelificadas a partir de emulsion-gels de agar y k-carragenato y aerogeles cargados de aceite como encapsulantes de un bioactivo lipofílico como la curcumina. Los resultados mostraron que el tipo de polisacárido y el estado físico de las redes del gel tenían un impacto en la estructura de los productos de la digestión. Por otro lado, se evaluó el potencial de los emulsion-gels basados en polisacáridos sulfatados (k-carragenato y agar) para la producción de un material capaz de simular tejido graso. Los resultados evidencian que los emulsions-gels de agar son adecuadas para producir materiales que simulan las propiedades dieléctricas para imitar tejidos de bajo y alto contenido en agua. / [CA] L'objectiu d'aquesta tesi doctoral ha sigut, el disseny i caracterització estructural d'estructures tipus gel, basades en polisacàrids extrets de biomassa aquàtica amb interès per a aplicacions relacionades amb l'alimentació. Les propietats dels polisacàrids extrets d'algues i plantes aquàtiques, són adequades per a produir diferents estructures tipus gel basades en la formació de xarxes reticulades, com a hidrogels, aerogels i emulsió-gels. En la primera part d'aquesta tesi es van investigar els diferents mecanismes de gelificació de polisacàrids sulfatats, així com els paràmetres que afecten l'estructura i les propietats funcionals dels hidrogels obtinguts. Sobre la base dels resultats, es va avaluar la potencial aplicació dels hidrogels i aerogels d'agar i k-carraguenina per a encapsular una proteïna alimentària model com la caseïna, explorant així l'efecte protector contra la hidròlisi enzimàtica després de digestions gastrointestinals simulades. A la segona part d'aquesta tesi, es van desenvolupar estructures d' aerogels mitjançant la valorització d'una font de biomassa residual infrautilitzada, com és el Arundo donax. Amb aquesta biomassa es van generar fraccions cel·lulòsiques amb diferents graus de purificació i extractes bioactius solubles en aigua, que posteriorment es van utilitzar per a produir aerogels bioactius híbrids. L'estructura altament porosa i l'elevada capacitat de sorció dels aerogels els converteixen en excel·lents candidats per a la substitució dels coixinets absorbents per a mantenir la qualitat dels productes carnis envasats. Els emulsió-gels són reconeguts pel seu gran potencial com a ingredients funcionals en la indústria alimentària com a modificadors de textura i com a substituts de greixos sòlids. A més, poden utilitzar-se com a vehicle per a l'alliberament controlat de compostos bioactius liposolubles. Així, a l'última part d'aquesta tesi, es va investigar la naturalesa de les interaccions entre els components dins les formulacions d' emulsió-gels basades en polisacàrids i es va relacionar amb la seua estructura i comportament mecànic i reològic. Després d'estudiar el mecanisme de gelificació dels emulsió-gels de carraguenina, aquests sistemes es van adaptar i es van utilitzar per a dues aplicacions diferents, rellevants per als sectors de l' alimentació i la biomedicina. En primer lloc, es van produir i van avaluar estructures gelificades a partir de emulsió-gels d'agar i k-carraguenina i aerogels carregats d'oli com a encapsulants d'un bioactiu lipofílic com la curcumina. Els resultats van mostrar que el tipus de polisacàrid i l'estat físic de les xarxes del gel tenien un impacte en l'estructura dels productes de la digestió. D'altra banda, es va avaluar el potencial dels emulsió-gels basats en polisacàrids sulfatats (k-carraguenina i agar) per a la producció d'un material capaç de simular teixit gras. Els resultats evidencien que els emulsió-gels d'agar són adequats per a produir materials que simulen les propietats dielèctriques podentimitar teixits de baix i alt contingut en aigua. / [EN] The aim of this doctoral thesis was to design and characterize the structure of gel-like structures based on polysaccharides extracted from aquatic biomass, with interest for food-related applications. The properties of polysaccharides extracted from seaweeds and aquatic plants make them suitable to produce a range of gel-like structures based on the formation of interconnected networks, such as hydrogels, aerogels and emulsion-gels. In the first part of this thesis, the different gelation mechanism of sulphated polysaccharides and the parameters affecting the structure and functional properties of the obtained hydrogels were investigated. Based on the results, the potential application of agar and k-carrageenan hydrogels and aerogels to encapsulate a model food protein such as casein was evaluated, thus exploring the protective effect against the enzymatic hydrolysis upon simulated gastrointestinal digestions. In the second part of this thesis, aerogel structures were developed by valorising an underutilized waste biomass source such as Arundo donax. This biomass was used to generate cellulosic fractions with different purification degrees and water-soluble bioactive extracts, which were subsequently used to produce hybrid bioactive aerogels. The highly porous structure and high sorption capacity of aerogels make them excellent candidates for the replacement of absorbent pads to maintain the quality of packaged meat products. Emulsion-gels are recognized for their great potential as functional ingredients in the food industry to modify texture and for solid fat replacement. Moreover, they can be used as a delivery vehicle for the controlled release of fat-soluble bioactive compounds. Thus, in the last part, the nature of interactions between the components in polysaccharide-based emulsion-gel formulations was investigated and related to their structure and mechanical and rheological behavior. After studying the gelation mechanism of carrageenan emulsion-gels, these systems were adapted and used for two different applications relevant to the food and biomedicine sectors. Firstly, oil-filled gel-like structures from agar and k-carrageenan emulsion-gels and oil-filled aerogels were produced and evaluated as carriers of a lipophilic bioactive such as curcumin. The results showed that the polysaccharide type and the physical state of the gel network had an impact on the structure of the digestion products. On the other hand, the potential of emulsion-gels based on sulphated polysaccharides (k-carrageenan and agar) for the production of tissue mimicking phantoms was evaluated. The results evidence that the agar emulsion-gels are suitable to produce materials simulating the dielectric properties to mimic low- and high-water content tissues. / Synchrotron experiments were performed at NCD beamline at ALBA Synchrotron with the collaboration of ALBA staff (2018022638 project). This work was financially supported by the grant RTI2018-094268-B-C22 (MCIU/AEI/FEDER, UE). Part of this work was supported by the COST Action ES1408 European network for algal-bioproducts (EUALGAE). Cynthia Fontes-Candia is recipient of a pre-doctoral grant from CONACYT (MEX/Ref. 306680). The projects RTI2018-094268-B-C22 and RTI2018-094408-J-I00 were funded by MCIN/AEI/10.13039/501100011033 and by “ERDF A way of making Europe”. This work has also received financial support from project PID2019-107663RB-I00 from the Spanish Ministry of Science and Innovation (MICINN). Cynthia Fontes-Candia is recipient of a pre-doctoral grant from CONACYT (MEX/Ref. 306680). Marta Martinez-Sanz is recipient of a Juan de la Cierva (IJCI-2015-23389) contract from the Spanish Ministry of Economy, Industry and Competitiveness. / Fontes Candia, C. (2022). Development and Characterization of Gel-Like Structures from Aquatic Biomass for Food Applications [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/181564 / Compendio

A curcumina é considerada um composto interessante para a indústria de alimentos por apresentar diversas propriedades bioativas e cor amarela intensa, porém sua elevada hidrofobicidade e instabilidade limitam sua aplicação em grande escala. Uma alternativa para a redução de tais problemas consiste na encapsulação deste bioativo em partículas lipídicas sólidas, que, quando estáveis, podem ser aplicadas para a produção de géis carregados com emulsões. Tais sistemas vêm sendo foco de diversas pesquisas por possibilitarem a obtenção de produtos com diferentes propriedades estruturais e sensoriais, a partir da aplicação combinada de diferentes agentes gelificantes e tensoativos. Nesse contexto, o presente projeto de mestrado teve como principais objetivos: a produção, caracterização e estudo da estabilidade de géis carregados com micropartículas lipídicas sólidas (MLS), produzidos com isolado proteico de soja (IPS) comercial, na presença e ausência de polissacarídeos (goma xantana - GX e goma locusta - GL), bem como a avaliação da estabilidade da curcumina encapsulada nos diferentes sistemas. Para o desenvolvimento desse estudo comparativo, três formulações de géis não-carregados, obtidos a frio, foram selecionadas: formulação G1 (15% IPS, 10 mM CaCl2, na ausência de polissacarídeos), formulação G2 (15% IPS, 0,1% GX e 5 mM de CaCl2) e formulação G3 (15% IPS, 0,2% GL e 15 mM CaCl2), todas em pH 7 e pré-aquecidas a 80 °C por 30 minutos. Tais sistemas foram utilizados também para a produção de géis carregados com MLS de estearina de palma, estabilizadas com tween 80 e span 80. Géis carregados e não-carregados foram adequadamente caracterizados a partir de ensaios de perfil de textura, avaliações da capacidade de retenção de água, microscopia eletrônica de varredura, microscopia confocal de varredura a laser e ensaios reológicos de pequena e grande deformação. Os resultados obtidos mostraram que a presença dos diferentes polissacarídeos alterou de formas distintas a organização estrutural dos géis de IPS, porém, em ambos os casos, as interações entre os biopolímeros resultaram no fortalecimento das estruturas formadas. Além disso, foi verificado que, nos géis carregados, as MLS mostraram-se ativas, fortalecendo a estrutura dos diferentes sistemas analisados. Já a partir do estudo da estabilidade da curcumina encapsulada nos diferentes sistemas, verificou-se que, o bioativo encapsulado em MLS em dispersão apresentou elevada estabilidade ao longo dos 60 dias de armazenamento, por outro lado, em géis carregados, a estabilidade da curcumina foi reduzida após 15 dias de estocagem. Esses resultados estão possivelmente relacionados às alterações estruturais dos géis carregados, verificados a partir de análises de perfil de textura e capacidade de retenção de água, que levaram ao colapso dos sistemas entre os dias 30 e 40 de armazenamento, indicando a necessidade de melhorias nas formulações utilizadas. / Curcumin is considered an interesting compound for the food industry, once it presents many bioactive properties and an intense yellow color, however its high hydrophobicity and instability limit its large-scale application. One of the alternatives applied in order to reduce these problems, consists in encapsulating this bioactive in solid lipid particles, which can also be applied for the production of emulsion filled gels. These systems have been frequently studied, once they allow the obtation of products with different structural and sensory properties, through the combined application of different gelling agents and surfactants. In this context, the objectives of this study were: the production, characterization and evaluation of the stability of cold-set emulsion filled gels, produced with comercial soy protein isolate (SPI), at presence and absence of polysaccharides (xanthan gum - XG and locust bean gum - LBG), and also the evaluation of the stability of encapsulated curcumin at the diferente systems. In order to develop this comparative study, three formulations of cold-set unfilled gels were selected: formulation G1 (15% SPI, 10 mM CaCl2, without polysaccharides), formulation G2 (15% SPI, 0,1% XG e 5 mM de CaCl2) and formulation G3 (15% SPI, 0,2% LBG and 15 mM CaCl2), all of them produced at pH 7 and pre-heated at 80 °C for 30 minutes. These systems were also applied for the production of emulsion filled gels thorugh the incorporation of solid lipid microparticles (SLM) of palm stearine, stabilized with tween 80 and span 80. Unfilled and emulsion filled gels were characterized through texture profile analysis, water holding capacity evaluations, scanning electron microscopy, confocal laser scanning microscopy and rheological tests (small and large deformations). The results showed that the presence of the polysaccharides - XG and LBG - altered in different ways the structural organizations of the SPI gels, however, in both cases, the interactions between the biopolymers resulted in the strengthening of the structures. Besides, it was verified that the SLM incorporated at EFG were active, reinforcing the structures of the different systems analyzed. On the other hand, through the evaluation of encapsulated curcumin stability, it was verified that the bioactive encapsulated in SLM dispersions presented high stability throughout the 60 days of storage, on the other hand, in EFG, the stability of curcumin started to decrease after 15 days of storage. These results are probably related to the structural alterations of EFG, verified through texture profile analysis and water holding capacity evaluations, which led to the collapse of the systems after 30-40 days of storage, indicating that, in all cases, formulation improvements are required.

Le projet de la thèse a consisté au développement et à l’évaluation des performances d’une mousse syntactique phénolique pour la réalisation d’un système sandwich multicouche (cœur/peau en matériau composite). Il permet d’assurer la protection thermique, mécanique et au feu en particulier contre l’impact d’un feu torche. Un feu torche peut survenir sur un site pétrochimique suite à l’inflammation d’une fuite de fluides inflammables sous pression pouvant être très dévastateur par son effet abrasif et le flux convectif et radiatif intense. Le travail s’est essentiellement axé sur l’étude de l’efficacité de la mousse syntactique phénolique à partir d’une analyse de la relation microstructure-propriété. Les exigences de mise en œuvre ont imposé une maîtrise de la formulation par une bonne compréhension de la réactivité de la résine, notamment par rapport aux différentes transformations physiques (gélification, vitrification) qui ont lieu pendant le processus de réticulation. Il s’agit alors d’optimiser le dosage des différents composés actifs et additifs vis-à-vis des contraintes de mise en œuvre afin de parvenir à des propriétés optimales du matériau final. L’efficacité de ce dernier dans les conditions normales d’utilisation a été déterminée par une phase d’expérimentation complète sur ses propriétés mécaniques, thermiques et thermomécaniques. Des tests au feu ont permis d’étudier son comportement au feu afin de vérifier ses propriétés protectrices sous l’impact d’une flamme issue d’un feu torche. Enfin, un essai instrumenté capable de reproduire en condition réelle une fuite de gaz de propane à haute pression a été mis au point pour évaluer la performance au feu torche d’un prototype industriel complet. En parallèle, un modèle numérique simplifié a été proposé afin de simuler l’impact d’un tel feu. / This work consisted in the development and the evaluation of a phenolic syntactic foam performance for the production of a multilayer sandwich system (core/skin in composite material). It ensures thermal, mechanical and fire protection, in particular against the impact of a jet fire. A jet fire can occur on a petrochemical site resulting from the combustion of a fuel continuously released under pressure. It can be very devastating for its abrasive effect and intense convective and radiative flux. The work focuses mainly on the study of the effectiveness of the phenolic syntactic foam through the analysis of the relationship microstructure-propriety. The manufacturing process requirements imposed to control the elaboration via a good understanding of the reactivity of the resin, especially in relation to various physical transformations (gelation, vitrification) that take place during the curing mechanisms. That involves optimizing the proportions of the various active compounds and additives depending on the working conditions in order to achieve optimal properties of the final material. The effectiveness of this final material under normal conditions of use was determined by a complete testing phase on its mechanical, thermal and thermomechanical properties. Fire tests were also conducted to investigate the material burning behavior to ensure its protective properties under a jet flame impact. Finally, a large-scale instrumented test, reproducing in real conditions a propane gas leak at high pressure, was developed to evaluate the resistance to a jet fire of a complete industrial prototype. In parallel, a simplified numerical model was also proposed to simulate the impact of such a fire.

Les substituts osseux synthétiques servent au remplacement temporaire des tissus osseux, favorisent la formation, la croissance et la survie de l’os et sont biorésorbables. Aucun matériau monophasé ne remplissant complètement ces exigences, un matériau composite bioinspiré est une alternative possible. L’objectif de cette thèse était par conséquent d’étudier la synthèse et les propriétés de deux composites biocéramiques/biopolymères : des hydrogels physiques de chitosane minéralisés avec de l’apatite, et une hardystonite architecturée imprégnée par des hydrogels physiques de chitosane. Afin d’obtenir le premier matériau, deux approches ont été développées. La première a consisté à fabriquer des hydrogels physiques de chitosane puis à les minéraliser avec de l’apatite ; la formation de microcapillaires se produit avec des conditions de synthèse spécifiques, et les précipités d’apatite ont été trouvés uniquement à la surface des hydrogels. La seconde approche consiste à convertir des suspensions homogènes contenant le phosphate de calcium et le chitosane en hydrogels de chitosane minéralisés par l’apatite. Les suspensions ont été préparées soit avec un mélange simultané, soit avec des mélanges successifs de suspensions phosphates de calcium avec les solutions de chitosane. Des agrégats minéraux plus petits avec une distribution plus uniforme ont été formés avec la méthode des mélanges successifs. Cela est attribué à une meilleure homogénéité, une viscosité plus faible et l’absence de chitosane. De manière générale, trois paramètres influencent les propriétés mécaniques d’hydrogels de chitosane minéralisés : la base utilisée pour la gélification (déterminant la vitesse de gélification : une grande vitesse conserve l’enchevêtrement des chaînes, résultant en une meilleure élasticité) ; la densité de la réticulation physique (cela induit un module de conservation plus important) et la force ionique (qui mène au désenchevêtrement des chaînes de chitosane, donc, à un faible module de conservation). Cette compréhension a permis l’utilisation de ces suspensions de phosphate de calcium-chitosane en tant qu’encre pour l’impression 3D. Les hydrogels de chitosane et les hydrogels minéralisés ne sont pas cytotoxiques. Pour fabriquer le second matériau, une encre pré-céramique a été imprimée en 3D puis frittée pour former une céramique d’hardystonite cristalline. Les scaffolds d’hardystonite ont été imprégnés par la solution de chitosane, converties ensuite en hydrogels physiques de chitosane. A plus forte concentration de chitosane, la viscosité de la solution était plus grande et l’imprégnation de la matrice plus lente. Avec une vitesse de gélification plus importante, qui dépend de la base utilisée pour la gélification, la perte de poids est plus faible pendant la gélification. L’hydrogel de chitosane a partiellement rempli les pores participant au support de charges externes et à la dissipation d’énergie par rupture. / Bone substitutes, an approach to attend social demand for bone healing and reparation, are temporary replacements of bone tissue, promote bone formation and growth and finally are bioresorbed. No single material meets these requirements; an alternative is a bioinspired composite material. The objective of this thesis was thus to study the synthesis and properties of two bioceramics/biopolymer composites: chitosan physical hydrogels mineralized with apatite and hardystonite scaffolds impregnated with chitosan physical hydrogels. To obtain the first material, two strategies were developed. The first one consisted in the fabrication of chitosan physical hydrogels and its subsequent mineralization with apatite; the formation of micro-capillaries occurred under particular synthesis conditions, and apatite precipitates were found only on the surface of hydrogels. The second strategy consisted in a simultaneous conversion of chitosan-calcium phosphate suspensions into chitosan-apatite hydrogels. The suspensions were prepared by sequential or simultaneous mixing of calcium and phosphate suspensions with chitosan solutions. Smaller and more uniformly distributed mineral aggregates were formed following sequential mixing, attributed to higher homogeneity, lower viscosity and no-presence of chitosan. This enabled the use of these chitosan-calcium phosphate suspensions as inks for 3-D printing. In general, three factors impacted the mechanical properties of mineralized chitosan hydrogels: the base used for gelation (determining the gelation rate: a higher rate preserved chain entanglement, resulting in higher elasticity); the density of physical crosslinks (hence a higher storage modulus) and the ionic strength (that led to chitosan chain disentanglements, thus, low storage modulus). Chitosan hydrogels and mineralized hydrogels were not cytotoxic, having no deleterious effects on osteoblasts proliferation. To fabricate the second material, pre-ceramic ink was 3-D printed and then sintered to form crystalline hardystonite ceramic. Hardystonite scaffolds were impregnated with chitosan solution that was, next, converted to chitosan physical hydrogel. At higher chitosan concentration, viscosity of solution was higher and scaffold impregnation was lower. At higher gelation rate, which depend on base used for gelation, lower weight loss during gelation. Chitosan hydrogel partially filled the pores contributing to bearing of external loads and to energy dissipated by fracture.

The structure of 11S cruciferin has been solved; however, how the individual subunits contribute to its physico-chemical and functional properties are not well known. The cruciferin isoforms in Arabidopsis thaliana, CRUA, CRUB, and CRUC, were investigated with respect to their molecular structures and the relationship of structural features to the physico-chemical and functional properties of cruciferin using homology modeling and various analytical techniques. Comparison of these models revealed that hydrophobicity and electrostatic potential distribution on the surface of the CRUC homotrimer had more favorable interfacial, solubility, and thermal properties than those of CRUA or CRUB. Flavor binding and pepsin digestion were associated with hypervariable regions (HVRs) and center core regions, respectively, moreso for CRUA and CRUB homotrimers than for CRUC. Chemical imaging of a single cell area in wild type (WT) and double-knockout seeds (CRUAbc, CRUaBc, and CRUabC) using synchrotron FT-IR microscopy (amide I band, 1650 cm-1, νC=O) showed that seed storage proteins were concentrated in the cell center and protein storage vacuoles, whereas lipids were closer to the cell wall. Secondary structure components of proteins of double-knockout lines did not show major differences. Changes in protein secondary structure components of pepsin-treated CRUabC (CRUC) mutant were minimal, indicating low enzyme accessibility. A three-step chromatographic procedure allowed isolation of the hexameric form of cruciferin with high purity (>95%). Fourier transform infrared (FT-IR) and circular dichroism (CD) spectroscopic analysis of the secondary structure of these proteins revealed cruciferins were folded into higher order secondary structures; 44−50% β-sheets and 7−9% α-helices. The relative subunit ratio was approximately 1:3:6 (CRUA:CRUB:CRUC) in the WT cruciferin. The Tm values of purified cruciferin at pH 7.4 (μ = 0.0) were in the order of WT = CRUA = CRUB < CRUC. The order of surface hydrophobicity as determined by ANS (1-anilinonaphthalene-8-sulfonate) probe binding was CRUA > CRUB = WT >> CRUC. Intrinsic fluorescence studies revealed a compact molecular structure for the CRUC homohexamer compared to the CRUA and CRUB homohexamers. The order of emulsion forming abilities was CRUA = CRUB > WT > CRUC (no emulsion formation) and the order of heat-induced network structure strength was WT > CRUA = CRUB > CRUC (no gel formation). The inability of CRUC to form gels or emulsions may be attributed to its low surface hydrophobicity and molecular compactness. At pH 2.0, CRUC hexamers dissociated into trimers which allowed the formation of an O/W emulsion and heat-induced network structures. Solubility of cruciferin as a function of pH at low ionic strength gave two minima around pH 4 and 7.4 yielding a “W” shape solubility profile deviating from the typical “U” or “V” shape solubility profile of other 11S globulins. The high ionic strength (μ = 0.5) was not favorable for emulsification, heat-induced gel formation, or solubilization for all cruciferins. Furthermore, the CRUA and CRUB homohexamers exhibited rapid pepsinolysis, while the CRUC homohexamer and WT heterohexamer were digested more slowly. Although fairly well conserved regions were found in the primary structure of these three cruciferin subunits, differences were found in the hypervariable regions and extended loop regions resulting in slight differences in 3D structures and interactions that occur during association to form superstructures, such as hexamers. These differences were reflected in the physico-chemical and techno-functional properties of hexamers and trimers composed of each subunit. In silico predictions for certain functionalities were highly correlated with empirical data from laboratory experiments.

The light scattering methods were used for characterization of properties and formation of networks of different dimension, based on N-vinylcaprolactam (VCL). Formation of PVCL microgels in presence of poly(vinyl alcohol) as stabilizer was studied. Size of resulting microgels strongly depends on the temperature and heating rate: interparticle aggregation was observed during slow heating and intraparticle collapse during fast heating. Angular dependence of measured diffusion coefficient on the angle of observation was studied for the microgel in the swollen, shrunken and aggregated states. Thermo-sensitive microgels based on N-vinylcaprolactam and acetoacetoxyethyl methacrylate were prepared under surfactant free conditions. The presence of internal part with low thermo-sensitivity and highly thermo-sensitive outer part of the particle (the core-shell structure of microgel) was deduced from static and dynamic light scattering experiments. Results obtained from combined SLS and DLS show the change of conformation from &amp;quot;swollen&amp;quot; soft sphere to compact shrunken &amp;quot;hard sphere&amp;quot;. Thermo-sensitive microgel based on N-vinylcaprolactam and N-vinylpyrrolidone was used for investigation of the internal modes in microgel dispersion in the wide range of qRg values. Two internal motions and translation diffusion were observed in the asymptotic range. Angular dependence of the normalized diffusion coefficient showed power law behavior in this range. The experimentally determined value of exponent n = 0.96 was in good agreement with the value predicted for ZIMM limit for polymer chains with hydrodynamic interaction. The reduced first cumulant Ã*(q) reached a constant value in the range of large qRg values. Appearance of plateau value indicates ZIMM limit of hydrodynamic interaction but experimental value was much lower than the theoretically predicted plateau value for linear chains in good solution. 3,3?-(ethane-1,1-diyl)bis(1-vinyl-2-pyrrolidone) was used as a cross-linker of VCL in solution by radical polymerization. The network formation was investigated by dynamic light scattering. It was shown, that monitoring of the light scattered intensity in all cases is quite sensitive to detect the gelation threshold even in the presence of very low amount of cross-linker. The power law of time correlation function at the gel point is a sufficient but not a necessary condition for critical gelation. The exponent calculated from power law depends on cross-linker concentration and can be attributed to the degree of branching. Critical exponents obtained at the gel point by DLS and rheology for hydrogel system based on VCL and hydroxyethyl methacrylate were compared. The theoretically predicted equality of exponents from these methods was found as not valid at least for this studied system.

Research activities towards the self-assembly of small organic molecules building blocks which lead to form supramolecular gel has increased extensively during the past two decades. The fundamental investigations of the morphological properties and the mechanical properties of these supramolecular gels are crucial for understanding gelation processes. Most supramolecular gelators were discovered by serendipity, but nowadays ratiional design of new gelators has become somewh at feasible. As a consequence, an increasing number of multi stimuli-responsive and functional molecular gels are reported, offering great prospects with myriads of applications includ ing drug delivery and smart materials as shown in scheme 1. Scheme 1 Part 2: Synthesis of semiconductor nanocrystals In the last two decades, the synthetic development of semiconductor col loidal nanocrystals has been extended from the adjustment of their size, shape, and composition of the particles at the molecular level. Such adjustments of nanocrystals at the molecula r level might open different fields of applications in materials and biological sciences. I n this chapter, the concept of the shape contr ol synthesis of colloidal nanocrystals with a narrow size distribution, and the synthesis of composition dependent alloy type mat erials are described (Scheme 2). Scheme 2 Chapter 2: Synthesis of luminescent semiconductor nanocrystals Part 1: Cadmium deoxycholate: a new and efficient precursor for high ly luminescent CdSe nanocrystals This part demonstrates the sy nthesis of Cadmium deoxycholate (CdDCh2), an efficient Cd-precursor for the synthesis of high quality, monodisperse, multi color emittting CdSe Scheme 3 nanocrystals, while maintaining their high photoluminescent quantum efficiency (Scheme 3). The high thermal stability of CdDCh2 (decomposition temperature: 332 °C) was utilized to achieve high injection and growth temperatures (∼300 °C) for the syntheesis of red emitting nanocrystals with a sharp f ull width at half maximum (FWHM) and multiple excitonic absorption features. We believe that CdDCh2 can be useful for the prreparation of other nanomaterials such as CdS, CdTe and CdSe@CdS core-shell QDs. Part 2: Ligand mediated exccited state carrier relaxation dynamics of Cd1-xZnxSe1-ySy NCs derived from bile salts Bile salts of Cadmium and Zinc provide a convenient and inexpensive single step synthetic route for highly photoluminescent and stable semiconductor nanocrystals (NCs). The high thermal stabilities of Cadmium and Zinc deoxycholates (CdDCh2 and ZnDCh2) allowed us to fine-tune the synthesis of the NCs at high temperatures while maintaining the monodispersity, crystallinity and reproducibility (Scheme 4). Organic capping agent induced lattice strain affects the excited Scheme 4 state relaxation processes of the NCs. The analysis of photoluminescence decay profiles revealed that the average lifettime decreased with the increasing lattice strain of the NCs. A kinetic stochastic model of photoexcited carrier relaxation dynamics of NCs was employed to estimate the values of the radiative recombination rates, the photoluminescence quenching rates and the non-radiative recombination rates of the NCs. These data showed that the non-radiative relaxation rates and the numbeer of surface trap states increased with the incrreasing lattice strain of the NCs. Such types of NCs can have great potential in nonlinear optics, photocatalysis and solar cells. Chapter 3: Synthesis of organic-inorganic hybrid materials Part 1: Hierarchical self-assembly of photoluminescent CdS nanoparticles into bile acid derived organogel: morphological and photophysical properties In this part a strategy towards integrating photoluminescent semiconductor nanoparticles into a bio-surfactant derived organoggel has been reported. A facially amphiphilic bile thiol was used for capping CdS nanoparticless (NPs) which were embedded in a gel derived from a new bile acid organogelator in order to furnish a soft hybrid material (Scheme 5). The presence of CdS NPs in a well-ordered 1D array on the organogel network was confirmed using microscopic Scheme 5 techniques. Photophysical stuudies of the gel–NP hybrid revealed resolved excitation and emission characteristics. Time resolved spectroscopic studies showed that the average lifetime value of the CdS NPs increased in the gel state compared to the sol phase. A kinetic model was utilized to obtain quantitative information about the different decay pathways of the photoexcited NPs in the sol and gel states. Part 2: A novel strategy towards designing a CdSe quantum dot–metallohydrogel composite material This section describes an efficiient method to disperse hydrophobic CdSe quaantum dots (QDs) in an aqueous phase using cetyltriimethylammonium bromide (CTAB) micelles without any surface ligand exchange. The water soluble QDs were then embedded in the 3D self-assembled fibrillar networks (SAFINs) of a hydrogel showing homogeneous dispersibility as eviidenced by Scheme 6 optical and electron microscopico techniques (Scheme 6). The photophyssical studies of the hydrogel–QD from composite are reported for the first time. These composite materials may have potential applications in biology, optoelectronics, sensors, non-linear optics and materials science. Part 3: Photophysical aspectts of self-assembled CdSe QD-organogel hyybrid and its thermoresponsive properties A luminescent hybrid gel was constructed by incorporating CdSe quantuum dots (QDs) in a facially amphiphilic bile acid derived dimeric urea organogel throough non-covalent interaction between ligands capped on QDs surface and hydrophobic pockets of the gel (Scheme 7). The optical transparency of the hybrid materials and the dirrectionalities of the QDs in the gel medium were confirmed by photophysical and microscopic studies. The detailed excited state dynamics of the QD–organogel hybrid has been reported for the first time with the help of lifetime analysis and a kinetic decay model, and thee data revealed that the average lifetime of the QDs decreased in the gel medium. The reversible thermoresponsive behavior of the QD doped organogel was investigated by steady-state fluorescence spectroscopy. W e believe that the results obtained herein provides a route to develop a thermoresponsive system for practical application, especially because of the spatial assembly between soft organic scaffolds and colloidal QDs. Scheme 7 Part 4: In-situ formation of luminescent CdSe QDs in a metallohydrogel: a strategy towards synthesis, isolation, storage and re-dispersion of the QDs A one step, in-situ, room temperature synthesis of yellow luminesce nt CdSe QD was achieved in a metallohydrog el derived from a facially amphiphilic bile salt, resulting in a QD-gel hybrid (Scheme 8). T he ordered self-assembly and homogeneous distribution of the CdSe QDs in the hydrogel network was observed from optical and electro n micrographs. The different excited state behav iors of the hybrid were revealed for the fir st time using time resolved spectroscopy. Ad ditionally, we described the successful isolation of the photoluminescent CdSe QDs from the gel followed by their re-dispersion in an organic solvent using suitable capping ligands. Scheme 8 Chapter 4: Facially a mphiphilic bile acid derived meta llohydrogel: an efficient template for th e enantioselective Diels-Alder reactio n An enantioselective Diels-Ald er reaction mediated by a facially amphiphilic bile acid derived metallogel scaffold has been a chieved (Scheme 9). Different hydrophobic domains present in Scheme 9 the gel appear to facilitate the enantioselective reaction. Various spectro scopic and electron microscopic techniques were employed to understand the possible reasons for the stereoselectivity in the gel. Subsequently, different counter anion s dependent rate accelerations and induced enantioselectivity in the ZnCh2 gel were studied in detail. These preliminary results of the non-covalent based supramolecular heterogeneous catalysis offer new possibilities for using metallogels as nanoreactors for different stereoselective reactions.

Dans le lait on peut distinguer les protéines sériques et les caséines. Les protéines sériques sont des protéines globulaires qui se trouvent dans le sérum du lait et elles sont connues pour leurs propriétés fonctionnelles exceptionnelles. Quand une solution de protéines sériques est chauffée, elles perdent leur structure native et peuvent s'agréger. Elles forment des agrégats de différentes formes, tailles et densités : des cylindres, des agrégats fractals, des microgels et des agrégats fibrillaires. De l'autre côté, les caséines sont organisées dans des micelles de caséine d'un rayon environ 100-200 nm stabilisées par du phosphate de calcium colloïdal.Au cours de ce travail, nous avons cherché à comprendre comment les agrégats de protéines sériques pouvaient être utilisés en mélange avec les micelles de caséine pour obtenir et contrôler la texture de produits laitiers. Dans un premier temps, nous avons étudié le processus de « cold gelation » induit par ajout de calcium et/ou acidification d'agrégats et de microgels de protéines sériques seuls. Dans une deuxième partie, nous nous sommes intéressés à la fonctionnalité des agrégats dans les mélanges plus complexes avec les autres protéines laitières et en présence de minéraux. L'addition de petites quantités d'agrégats fractals dans des suspensions de micelles diminuait leur température critique de gélification, augmentait le module élastique et diminuait la synérèse des gels.Les agrégats de protéines sériques peuvent être utilisés pour modifier la viscosité des mélanges, comme gélifiant ou pour enrichir la teneur en protéine du milieu sans en augmenter la viscosité. / The proteins of milk can be divided into whey proteins and caseins. Whey proteins are compact globular proteins that are found in the aqueous phase of milk. They are well-known for their exceptional functional properties. Upon heating, individual whey proteins denature and aggregate, forming aggregates of different morphologies and sizes, such as strands, fractal aggregates, microgels and fibrillar aggregates, depending on the heating conditions. On the other hand, the caseins in milk are organized in complex protein units with a diameter of 100-200 nm called casein micelles stabilized by colloidal calcium phosphate (CCP).The current work is an endeavor to understand how whey protein aggregates might be used in mixtures with other dairy proteins, such as casein micelles, in order to get a particular texture in a dairy product. We first extended the understanding of so-called “cold gelation” of pure WPI aggregates induced by calcium and acidification and then studied how the aggregates work in more complex mixtures of proteins and minerals. Interestingly, addition of small amounts of fractal aggregates to suspensions of casein micelles has been demonstrated to decrease the critical gelation temperature, increase the elastic modulus and decrease the syneresis of the gels.The aggregates are to be used to modify the viscosity of dairy products, as a gelling agent and for protein enrichment. The properties of strands, fractal aggregates and microgels have been studied and compared. WPI aggregates might be considered as “clean label” texturizing ingredients that do not require approval from the European Food Safety Authority (EFSA).

The consumption of omega-3 fatty acids and phytosterol promotes the reduction of cholesterol and triacylglycerol levels. However, such compounds are susceptible to oxidation, which hampers their application. First, the aim of this work was to encapsulate echium oil (Echium plantagineum L.), source of omega-3 fatty acids, with hydrophilic phenolic compounds (sinapic acid and rutin) by double emulsion followed by complex coacervation in order to evaluate the best hydrophilic phenolic compound. In this case, sinapic acid showed better performance as antioxidant. Then, the second objective of this work was to study the microencapsulation of echium oil by complex coacervation using gelatin-arabic gum and gelatin-cashew gum as wall materials and sinapic acid and transglutaminase as crosslinkers. In this step, it was possible to observe that sinapic acid, besides to be an antioxidant, could also act as crosslinker. So, the third objective was to study the effect of sinapic acid in echium microparticles obtained by emulsion followed by spray or freeze drying using arabic gum as carrier agent in order to compare different encapsulation techniques. In addition to these methods, the fourth objective was to compare these techniques already mentioned to the combination of microfluidic devices and ionic gelation in order to encapsulate echium oil. In this case, sinapic acid and quercetin were also incoporated in the microcapsules. All the microcapsules/ microparticles obtained in the mentioned different techniques presented characteristics feasible for application and also promoted the protection of the oil. However, the encapsulation by complex coacervation and the addition of sinapic acid as crosslinkers was the method choosen for the coencapsulation of echium oil and phytosterols since presented the better results. Moreover, the treatment GA075 (microcapsule with gelatin-arabic gum as wall materials and 0.075g sinapic acid/ g gelatin) promoted the better protection to the encapsulated compounds. In this way, this treatment was applied into yogurt and compared to the one with the compounds nonencapsulated and the yogurt control. The yogurt containing microcapsules, presented a pH range from 3.89-4.17 and titratable acidity range from 0.798-0.826%, with good sensorial acceptance. It was possible to apply the microcapsules in yogurt, without compromising the rheological properties and physicochemical stability of the product, obtaining a functional product rich in omega-3 fatty acids, phytosterols and phenolic compound. / O consumo de ácidos graxos ômega-3 e fitosterol promove a redução dos níveis de colesterol e triacilglicerol. No entanto, esses compostos são susceptíveis à oxidação, o que dificulta sua aplicação. Primeiramente, o objetivo deste trabalho foi encapsular o óleo de echium (Echium plantagineum L.), fonte de ácidos graxos ômega-3, com compostos fenólicos hidrofílicos (ácido sinápico e rutina) por emulsão dupla seguida de coacervação complexa com intuito de avaliar o melhor composto fenólico hidrofílico. Neste caso, o ácido sinápico apresentou melhor desempenho como antioxidante. Em seguida, o segundo objetivo deste trabalho foi estudar a microencapsulação do óleo de echium por coacervação complexa utilizando as combinações gelatina-goma arábica e gelatina-goma de caju como materiais de parede e ácido sinápico e transglutaminase como agentes de reticulação. Nesta etapa, foi possível observar que o ácido sinápico, além de ser um antioxidante, também pode atuar como agente de reticulação. Assim, o terceiro objetivo foi estudar o efeito do ácido sinápico em micropartículas de óleo de echium obtidas por emulsão seguida de atomização ou liofilização utilizando goma arábica como agente carreador, com a finalidade de comparar diferentes técnicas de encapsulação. Além desses métodos, o quarto objetivo foi comparar essas técnicas já mencionadas com a combinação de dispositivos microfluídicos e gelificação iônica utilizando o óleo de echium como composto bioativo. Neste caso, o ácido sinápico e a quercetina também foram incorporados nas microcápsulas. Todas as microcápsulas/ micropartículas obtidas pelas diferentes técnicas mencionadas apresentaram características viáveis para aplicação e também promoveram a proteção do óleo. No entanto, a encapsulação por coacervação complexa e a adição de ácido sinápico como reticulante foi o método escolhido para a coencapsulação de óleo de echium e fitosteróis, uma vez que apresentou melhor resultado. Além disso, o tratamento GA075 (microcápsula com gelatina-goma arábica como materiais de parede e 0,075g de ácido sinápico/ g gelatina) promoveu a melhor proteção aos compostos encapsulados. Desta forma, este tratamento foi aplicado em iogurte e comparado com o mesmo adicionado dos compostos não encapsulados e o iogurte controle. O iogurte contendo microcápsulas apresentou faixa de pH de 3,89-4,17 e acidez titulável de 0,798-0,826 %, com boa aceitação sensorial. Foi possível a aplicação das microcápsulas no iogurte, sem comprometer as propriedades reológicas e a estabilidade físico-química do produto, obtendo um produto funcional rico em ácidos graxos ômega-3, fitosteróis e compostos fenólicos.

A curcumina é considerada um composto interessante para a indústria de alimentos por apresentar diversas propriedades bioativas e cor amarela intensa, porém sua elevada hidrofobicidade e instabilidade limitam sua aplicação em grande escala. Uma alternativa para a redução de tais problemas consiste na encapsulação deste bioativo em partículas lipídicas sólidas, que, quando estáveis, podem ser aplicadas para a produção de géis carregados com emulsões. Tais sistemas vêm sendo foco de diversas pesquisas por possibilitarem a obtenção de produtos com diferentes propriedades estruturais e sensoriais, a partir da aplicação combinada de diferentes agentes gelificantes e tensoativos. Nesse contexto, o presente projeto de mestrado teve como principais objetivos: a produção, caracterização e estudo da estabilidade de géis carregados com micropartículas lipídicas sólidas (MLS), produzidos com isolado proteico de soja (IPS) comercial, na presença e ausência de polissacarídeos (goma xantana - GX e goma locusta - GL), bem como a avaliação da estabilidade da curcumina encapsulada nos diferentes sistemas. Para o desenvolvimento desse estudo comparativo, três formulações de géis não-carregados, obtidos a frio, foram selecionadas: formulação G1 (15% IPS, 10 mM CaCl2, na ausência de polissacarídeos), formulação G2 (15% IPS, 0,1% GX e 5 mM de CaCl2) e formulação G3 (15% IPS, 0,2% GL e 15 mM CaCl2), todas em pH 7 e pré-aquecidas a 80 °C por 30 minutos. Tais sistemas foram utilizados também para a produção de géis carregados com MLS de estearina de palma, estabilizadas com tween 80 e span 80. Géis carregados e não-carregados foram adequadamente caracterizados a partir de ensaios de perfil de textura, avaliações da capacidade de retenção de água, microscopia eletrônica de varredura, microscopia confocal de varredura a laser e ensaios reológicos de pequena e grande deformação. Os resultados obtidos mostraram que a presença dos diferentes polissacarídeos alterou de formas distintas a organização estrutural dos géis de IPS, porém, em ambos os casos, as interações entre os biopolímeros resultaram no fortalecimento das estruturas formadas. Além disso, foi verificado que, nos géis carregados, as MLS mostraram-se ativas, fortalecendo a estrutura dos diferentes sistemas analisados. Já a partir do estudo da estabilidade da curcumina encapsulada nos diferentes sistemas, verificou-se que, o bioativo encapsulado em MLS em dispersão apresentou elevada estabilidade ao longo dos 60 dias de armazenamento, por outro lado, em géis carregados, a estabilidade da curcumina foi reduzida após 15 dias de estocagem. Esses resultados estão possivelmente relacionados às alterações estruturais dos géis carregados, verificados a partir de análises de perfil de textura e capacidade de retenção de água, que levaram ao colapso dos sistemas entre os dias 30 e 40 de armazenamento, indicando a necessidade de melhorias nas formulações utilizadas. / Curcumin is considered an interesting compound for the food industry, once it presents many bioactive properties and an intense yellow color, however its high hydrophobicity and instability limit its large-scale application. One of the alternatives applied in order to reduce these problems, consists in encapsulating this bioactive in solid lipid particles, which can also be applied for the production of emulsion filled gels. These systems have been frequently studied, once they allow the obtation of products with different structural and sensory properties, through the combined application of different gelling agents and surfactants. In this context, the objectives of this study were: the production, characterization and evaluation of the stability of cold-set emulsion filled gels, produced with comercial soy protein isolate (SPI), at presence and absence of polysaccharides (xanthan gum - XG and locust bean gum - LBG), and also the evaluation of the stability of encapsulated curcumin at the diferente systems. In order to develop this comparative study, three formulations of cold-set unfilled gels were selected: formulation G1 (15% SPI, 10 mM CaCl2, without polysaccharides), formulation G2 (15% SPI, 0,1% XG e 5 mM de CaCl2) and formulation G3 (15% SPI, 0,2% LBG and 15 mM CaCl2), all of them produced at pH 7 and pre-heated at 80 °C for 30 minutes. These systems were also applied for the production of emulsion filled gels thorugh the incorporation of solid lipid microparticles (SLM) of palm stearine, stabilized with tween 80 and span 80. Unfilled and emulsion filled gels were characterized through texture profile analysis, water holding capacity evaluations, scanning electron microscopy, confocal laser scanning microscopy and rheological tests (small and large deformations). The results showed that the presence of the polysaccharides - XG and LBG - altered in different ways the structural organizations of the SPI gels, however, in both cases, the interactions between the biopolymers resulted in the strengthening of the structures. Besides, it was verified that the SLM incorporated at EFG were active, reinforcing the structures of the different systems analyzed. On the other hand, through the evaluation of encapsulated curcumin stability, it was verified that the bioactive encapsulated in SLM dispersions presented high stability throughout the 60 days of storage, on the other hand, in EFG, the stability of curcumin started to decrease after 15 days of storage. These results are probably related to the structural alterations of EFG, verified through texture profile analysis and water holding capacity evaluations, which led to the collapse of the systems after 30-40 days of storage, indicating that, in all cases, formulation improvements are required.