0 comportamento higroscópico do suco de laranja liofilizado, e aditivado com malto-dextrinas e lactose, e de misturas mecânicas do suco liofilizado com os aditivos secos, foi estudado através da cinética e das isotermas de sorção de água, em diferentes temperaturas. Avaliou-se as características espectrais no visível e ultravioleta, e o teor de vitamina C, de amostras de suco de laranja liofilizado expostas a diferentes umidades relativas e temperaturas. Estudou-se a influência do valor de pH e natureza do tampão sobre a retenção do limoneno emulsionado em soluções de lactose, liofilizadas. A liofilização praticamente não alterou o teor de vitamina C e as características espectrais do suco de laranja, mas aumentou o valor monomolecular da malto-dextrina (dextrose equivalente de 9 a 12%). A lactose liofilizada apresentou-se no estado amorfo. Os teores de umidade de equilíbrio das misturas aditivadas liofilizadas, foram menores que os das misturas mecânicas. Os aditivos reduziram a sorção de umidade em função do tempo. A retenção do limoneno foi influenciada pela sua concentração inicial, sendo que ocorreu a major perda, durante a liofilização na major concentração utilizada. / The higroscopic behavior of freeze-dried orange juice, with added maltodextrins and lactose and mechanical mixtures with this additives was studied through the kinetics and isoterms of water sorption in different temperatures. It was evaluated the spectral characteristics, in the visible and ultraviolet range, and the vitamin C content from samples of freeze-dried orange juice exposed at different relative humidities and temperatures. It was studied the influence of pH and buffer composition, on the limonene retention of freeze-dried emulsions. The spectral characteristics and vitamin C content showed no alterations after liofilization the maltodextrin (9-12 % dextrose equivalent monomolecular value increased. Freezedried lactose was amorphous. The equilibrium humidity content of the samples with additives were reduced when compared with mechanical mixtures. The additives also reduced the rate of water sorption. The limonene retention during freeze-drying was influenced by the initial concentration of the emulsion. The greater concentration studied showed the lower retention value.

MENVSC / Department of Ecology and Resource Management / See the attached abstract below

Ces travaux de thèse visent à trouver des solutions pour minimiser autant que possible la présence de microporosités dans les alliages aéronautiques conventionnels et nouveaux. Ces microporosités résultent notamment de la réaction de l’aluminium liquide, durant la phase de coulée, avec l’hydrogène apportée par la vapeur d’eau contenue dans les réfractaires. La plupart de ces produits sont des bétons hydrauliques à matrice cimentaire alumineuse. Dans une première étape, l’identification physico-chimique et minéralogique des matériaux et des produits élaborés a été réalisée. Le comportement thermo-hydrique de différentes de bétons et de pâtes cimentaires durcies a ensuite été étudié par des essais de reprise d'humidité réalisés dans diverses conditions hygrothermiques, y compris à températures élevées (300°C). On montre ainsi que les variations hydriques dépendent fortement de la nature du liant, en particulier de sa teneur en alumine. Les phénomènes de physisorption et chimisorption sont mobilisés. Parallèlement, le comportement thermique d'une goulotte réfractaire a été modélisé, première étape pour quantifier les transferts de vapeur d’eau au sein des matériaux. Des mesures continues de température et de pression ont été obtenues sur des éprouvettes de pâtes et de bétons diversement conditionnées, placées au contact d’une frette métallique maintenue à 700°C. D’autres mesures ont été faites. Elles ont consisté à immerger des échantillons (pâtes et bétons), préalablement conservés dans différentes conditions hygrothermiques, dans l’aluminium liquide, afin de comparer leur réactivité en termes de relargage d’hydrogène, d’oxygène et de vapeur d’eau / This thesis aims to find solutions to minimize as much as possible the presence of micro-porosities in conventional and new aerospace alloys. These micro-porosities resulting especially from the reaction of the molten aluminum, during the casting phase, with the hydrogen provided by the steam contained in the refractory castables. Most of these castables are composites obtained with hydraulic binders based on aluminous cements. Firstly, a physico-chemical and mineralogical characterization of the basic materials and processed products was performed. Then, the thermo-hydric behavior of different castables and hardened cement pastes (principal source of the physical water and the chemical water) was then studied by moisture pick up tests made in various hygrothermal conditions, including at high temperatures (300 °C). It was shown that the hydric variations amplitudes strongly depend on the binder’s nature, in particular on its alumina content. The phenomena of physisorption and chemisorption are mobilized. Meanwhile, the transient thermal behavior in the time through the thickness of a refractory launder was modeled as a first step to quantify the water vapor transfer in the materials. Continuous measurements of temperature and pressure were obtained on pastes and concretes samples variously packged, placed in contact with a heated metal band maintained at 700 °C. Other measurements were made. They consisted into immersing samples (cement pastes and castables), previously stored in different hygrothermal conditions in liquid aluminum, in order to compare their reactivity in terms of release of hydrogen, oxygen and water vapor

No description available.

Abstract Food sustainability depends significantly on packaging since it helps maintainfood safe and fresh throughout its shelf life, resulting in the least amount ofwaste and the least negative environmental impact. The main objective of thisstudy is to determine the adsorbed and released amount of antimicrobial agents(benzoic acid and thymol) on modified calcium carbonate (MCC) by investigating adsorption isotherm at 25°C and desorption kinetics at both 22°C and5°C of anti-microbial to identify potential solutions to enhance the long-termsustainability of fresh products such as meat. These agents were incorporatedinto specialized food pads to mitigate bacterial growth in food packaging instead of being directly added to the food. Additionally, the study aimed to determine the amount of carbon dioxide generated when MCC, used as an adsorbent in combination with citric acid, comes into contact with the meat liquid,as this has an impact on the growth of aerobic microorganisms.The findings revealed that MCC adsorbed 44% and 55% of the initial quantities of benzoic acid (BA) and thymol, respectively. Furthermore, after 12 seconds from an initial adsorption amount of 19 mg/g, the maximum amount ofthymol released from MCC was measured at 0.120 mg/ml (approximately0.126%). Similarly, for an initial adsorption amount of 15 mg/g, the quantityof BA released was found to be 0.080 mg/ml (approximately 0.106%). TheUV-spectrophotometer was utilized to determine the amounts of adsorbed anddesorbed anti-microbial agents, while Checkmate 3 was used to assess the release of carbon dioxide.Significantly, the utilization of food pads demonstrated a significant enhancement in the release of carbon dioxide. Interestingly, the presence of anti-microbial agents did not have any influence on the generation of carbon dioxide.This research provides valuable insights into the potential application of foodpads and MCC as effective strategies for preserving fresh meat products bycontrolling microbial activity and promoting sustainability. / Sammanfattning Livsmedelshållbarhet beror i hög grad på förpackningar eftersom det hjälpertill att hålla maten säker och fräsch under hela dess hållbarhetstid, vilket resulterar i minskad mängd avfall och mindre negativ miljöpåverkan. Huvudsyftetmed denna studie var att bestämma den adsorberade och frigjorda mängdenantimikrobiella medel (bensoesyra och tymol) på modifierat kalciumkarbonat(MCC) genom att undersöka adsorptionsisoterm vid 25°C och desorptionskinetiken vid både 22°C och 5 °C av antimikrobiellt medel för att identifierapotentiella lösningar för att förbättra den långsiktiga hållbarheten för färskaprodukter som kött. Dessa medel inkorporerades i specialiserade food pad föratt mildra bakterietillväxt i livsmedelsförpackningar istället för att läggas direkt till maten. Dessutom syftade studien till att fastställa mängden koldioxidsom genereras när MCC, som används som adsorbent i kombination med citronsyra, kommer i kontakt med köttvätskan, eftersom detta har en inverkan påtillväxten av aeroba mikroorganismer.Resultaten visade att MCC adsorberade 44 % och 55 % av de initiala mängderna bensoesyra (BA) respektive tymol. Vidare, efter 12 sekunder från eninitial adsorptionsmängd på 19 mg/g, mättes den maximala mängden tymolsom frigjordes från MCC till 0,120 mg/ml (ungefär 0,126%). På liknande sätt,för en initial adsorptionsmängd på 15 mg/g, visade sig mängden frisatt BA vara0,080 mg/ml (ungefär 0,106%). UV-spektrofotometern användes för att bestämma mängderna av adsorberade och desorberade antimikrobiella medel,medan Checkmate 3 användes för att bedöma frisättningen av koldioxid.Betecknande nog visade användningen av food pad betydande förbättring avutsläppet av koldioxid. Intressant nog har närvaron av antimikrobiella medelinte haft någon inverkan på genereringen av koldioxid. Denna forskning gervärdefulla insikter om den potentiella tillämpningen av food pad och MCC someffektiva strategier för att bevara färska köttprodukter genom att kontrolleramikrobiell aktivitet och främja hållbarhet.

Denna avhandling presenterar experimentella studier av polyelektrolytadsorption på motsatt laddade ytor, där substrat av både kiseloxid och blekt barrsulfatmassa har använts. Ett huvudsakligt syfte med denna forskning var att karaktärisera konformationen hos adsorberade skikt av katjonisk polyakrylamid (CPAM) i jämförelse med katjonisk dextran (Cdextran) och relatera denna information till inbindningskapaciteten av kolloidal kiselsyra. Ett andra syfte i denna avhandling var att studera kinetiken för sekventiell adsorption av polyamidamin epiklorhydrin (PAE) och karboxymetyl cellulosa (CMC) på massafibrer och att bestämma adsorptionsisotermer för deponering av polyelektrolyter skikt för skikt på massafibrer. Adsorptionen av CPAM på kiseloxidytor studeras med stagnationspunkts-reflektometri och kvartskristalls-mikrogravimetri för att bestämma adsorptionskinetiken och mättnadsadsorptionens beroende av polyelektrolytens laddningstäthet, pH och NaCl koncentration. Konformationen hos adsorberade skikt av CPAM och Cdextran bestämdes både före och efter sekundär tillsats av kolloidal kiselsyra (CS) och adsorptionen av CS kvantifierades också som funktion av yttäckningen av polyelektrolyt. Resultaten indikerar att laddningstätheten hos CPAM kontrollerar den adsorberade mängden på kiseloxidytor vid låga NaCl koncentrationer. Både adsorptionen av CPAM och Cdextran på kiseloxid visades vara effektiv i NaCl koncentrationer upp till 1 M, vilket indikerar ett signifikant bidrag av icke-jonisk interaktion mellan polyelektrolyterna och kiseloxid. Adsorptionen av CS var högre på föradsorberad CPAM än Cdextran. Konformationen hos de adsorberade skikten efter tillsats av CS sågs expandera signifikant för skikt baserade på CPAM medan skikt av Cdextran vid låga salthalter verkade återta sin konformation efter en temporär expansion. I den andra delen av avhandlingen studerades sekventiell adsorption av PAE och CMC på massafibrer. Adsorptionsisotermer skikt för skikt på avkryllad massa visade att PAE adsorberade i större mängd än CMC, både i hänseende av massa och laddning. Adsorptionen av PAE var signifikant långsammare än CMC och adsorptionstiden till 90% av mättnadsadsorptionen bestämdes till 3 respektive 1 minut. Zetapotentialen för kryll bestämdes för adsorption av de två första polyelektrolytskikten och resultaten tydde på att kryllmaterialet omladdade inom en minut efter tillsatserna av polyelektrolyt. Reflektometriförsök inom sekventiell adsorption av PAE och CMC på kiseloxid antydde att den låga molekylviktsfraktionen av PAE störde uppbyggnaden av polyelektrolyt-multiskikten. / This thesis presents experimental studies of polyelectrolyte adsorption on oppositely charged surfaces, where substrates of both silica and bleached softwood kraft pulp were used. A major aim of this research was to characterise the conformation of adsorbed layers of cationic polyacrylamide (CPAM), in comparison to cationic dextran (Cdextran), and relate this information to the binding capacity of colloidal silica. A second aim in this thesis was to study the kinetics of the sequential adsorption of polyamide epichlorohydrine (PAE) and carboxymethyl cellulose (CMC) on pulp fibres, and to determine the adsorption isotherms for the layer-by-layer deposition of polyelectrolytes on pulp fibres. The adsorption of CPAM on silica surfaces was studied using stagnation point adsorption reflectometry and quartz crystal microgravimetry to determine its adsorption kinetics as well as the dependencies of polyelectrolyte charge densities, pH, and NaCl concentration on saturation adsorption. The conformation of adsorbed layers of CPAM and Cdextran, analysed in terms of amount of water and layer thickness, was determined both before and after the secondary adsorption of colloidal silica (CS), and the adsorption of CS was also quantified as a function of the surface coverage of the polyelectrolyte. Results indicate that the charge density of CPAM controlled the amount of the polyelectrolyte adsorbed on silica surfaces at low NaCl concentrations. The adsorption of both CPAM and Cdextran on silica was shown to be effective at up to 1 M NaCl concentrations, which indicates that non-ionic interactions between the polyelectrolytes and silica contribute significantly. CS adsorption was higher on pre-adsorbed CPAM than on Cdextran. The conformation of the adsorbed layer after CS addition was seen to expand significantly in CPAM-based layers, while the Cdextran layer appeared to restore its conformation after a temporary expansion at low salt concentrations. In the second part of the thesis, the sequential adsorption of PAE and CMC on pulp fibres was determined using the polyelectrolyte titration technique. Layer-by-layer adsorption isotherms derived on fractionated pulp showed that PAE adsorbed in higher amounts than CMC did, both in terms of adsorbed mass and adsorbed charge. The adsorption of PAE was significantly slower compared to CMC, and the adsorption times required to reach 90% of the saturation adsorption were 3 and 1 min, respectively. The zeta potential of pulp fines was determined for the adsorption of the two first polyelectrolyte layers, and data indicated that the fines recharge within one minute after the polyelectrolyte additions. Reflectometry experiments regarding the sequential adsorption of PAE and CMC on silica indicated that the low-molecular-weight fraction of PAE disturbed the formation of polyelectrolyte multilayers. / QC 20101112

M.Tech. (Department of Chemical Engineering, Faculty of Engineering and Technology), Vaal University of Technology. / In the present study, the removal of Ca2+ and Mg2+ from cooling tower water using Amberlite IR120 and Amberjet 1200 was studied by the application of one factor at a time method (OFAT) and response surface modelling (RSM). The effect of operational parameters such as contact time (min), pH, dosage (mL), concentration (mg/L) and temperature (K) were investigated using central composite design. The regeneration of the Amberlite IR120 and Amberjet were also studied. The purpose of the study was to apply OFAT and RSM to investigate and optimize the ion exchange operating parameters. Furthermore, the second-order empirical model that was developed, using the analysis of variance (ANOVA), presented a sufficient correlation to the ion exchange experimental data. The optimal ion exchange operating conditions for Amberlite IR120 and Amberjet 1200 were found to be: contact time was 120 min, dosage of 150mL, initial pH level of 2, concentration of 400mg/L and temperature of 343K. Regeneration of Amberlite IR120 and Amberjet 1200 using 0.5 M NaCl stripping solution initially showed an increase in % Ca2+ and Mg2+ removal, then a decrease in subsequent cycles. The correlation coefficients (R2) of Langmuir, Freudlich and Tempkin isotherms were found to range from 0.92 to 1 and this suggest that experimental data best described the models. However correlation coefficients (R2) for Dubinin–Radushkevich (D-R) model were found to range between 0.5 to 0.8 and this means that experimental data does not fit the model. Thermodynamic functions such as entropy (Δ𝑆𝑜), enthalpy (Δ𝐻𝑜) and change of free energy (Δ𝐺𝑜) were obtained from the gradient and intercepts of straight line graphs. The positive values of ΔG° were found meaning that the adsorption is not spontaneous and positive values of ΔH° were found meaning the endothermic type of adsorption which indicate the chances of physical adsorption.The correlation coefficient (R2) values of pseudo-first-order, pseudo-second-order and intraparticle models were found to range from 0.89 to 1 on both metals as shown in table 4.4. This observation clearly indicates that pseudo-first-order, pseudo-second-order and intraparticle diffusion models best describe the experimental data in the removal Ca2+ and Mg2+ from cooling tower water.

In this research, the adsorptive capacities of kenaf in the forms of chopped whole stalk, chopped core, and bast materials were evaluated for the removal of lead, zinc, and toluene from contaminated synthetic waste streams using traditional adsorption isotherm techniques. The effect of surface oxidation using ozone was observed with respect to the adsorption of metals. Hydraulic conductivity experiments were conducted to evaluate the head loss associated with packing a column with kenaf fibers and to determine the suitability of its use in dynamic packed column systems. B.E.T. surface areas were determined as well. Under increasingly stringent regulatory requirements, even low level organic and inorganic contamination (under 100 ppm) in surface and ground waters must be treated. This study is part of an ongoing multi-year research effort aiming to develop a kenaf-based biosorptive process to improve treatment of contaminated aqueous streams at reduced costs and technical complexity.

Abstract Biodegradable starch-glycerol based films were obtained. The influence of lipid compounds (palmitic, stearic and oleic acid), other polymers (hydroxypropylmethylcellulose and sodium caseinate) and bioactive compounds (¿-tocoferol, D-limonene and orange essential oil) on film properties (oxygen and water vapour barrier, optical, mechanical, nano- and microstructural). Furthermore the effect of storage time on films¿ properties was also considered. Fatty acids addition did not improve the water vapour ability of films except for non-stored saturated fatty acids containing films. X-ray diffraction results showed that cristallinity of films increased with storage time, thus increasing the stiffness and decreasing the gloss of films. Furthermore, crystallinity affected the water sorption capacity of films as function of relative humidity and temperature. Glass transition temperature of starch films varied with saturated fatty acids addition. However, oleic acid did not affect this parameter. The presence of fatty acids promoted the formation of V-type structures, thus indicatin the formation of amylose-lipid complexes that inhibited the developmet of other crystalline structures. The effect of the incorporation of other biopolymers to improve the functionality of starch films was also studied. Hydroxypropylmethylcellulose (HPMC) addition inhibited starch retrogradation. However, obtained films were more permeable, specially in case of oxygen. HPMC addition produced phase separation as it was observed by scanning electron microscopy. On the contrary, sodium caseinate incorporation (NaCas) allowed to obtain homogeneous films and less permeable to oxygen. Obtained films showed less mechanical resistance in comparison with pure starch films but a greater flexibility without increasing the water vapour permeability. Rearrangement of polymers chains during storage reduced the mechanical resistance, the extensibility and the gloss of composite films. Regarding the obtained results, the film including a starch:protein ratio of 50:50 was choosen as the film with the most adequate properties. Composite film (starch:Nacas ratio = 50:50) was studied as a matrix for the incorporation o active compounds (¿-tocopherol, D-limonene and orange essential oil). The effect of ¿-tocopherol addition was compared with the incorporation of oleic acid and their mixture. Lipids addition promoted phase separation between starch and NaCas due to the different interactions between each polymer and the lipids. Furthermore, oleic acid addition increased significantly the oxygen permeability whereas ¿-tocopherol greatly improved the antioxidant capacity of films without affecting the oxygen permeability. D-limonene and orange essential oil incorporation was carried out by forming rapeseed and soy nanoliposomes, which acted as carriers of bioactive components. Nanoliposomes incorporation was performed directly in starch-NaCas dispersions without any homogenization, to avoid nanoliposomes damages. Bioactive compounds addition did not confer antimicrobial capacity to the films (except for soy-orange oil nanoliposomes containing film) probably due to the high stability of nanoliposomes and the low antibacterial activity of D-limonene and orange essential oil. / Se han desarrollado y caracterizado films biodegradables a base de almidón de maíz y glicerol como plastificante, evaluando al mismo tiempo el efecto de la adición de componentes lipídicos (ácido palmítico, esteárico y oleico), otros polímeros (hidroxipropilmetilcelulosa y caseinato de sodio) y compuestos bioactivos (¿-tocoferol, aceite esencial de naranja y D-limoneno) sobre las propiedades de los films (propiedades barrera al vapor de agua y al oxígeno, ópticas, mecánicas, micro y nanoestructurales). Asimismo se evaluó la influencia del tiempo de almacenamiento en las propiedades de los films. La adición de ácidos grasos no mejoró notablemente la permeabilidad al vapor de agua excepto en el caso de los films con ácidos grasos saturados y solo en films no almacenados. Los resultados de difracción de rayos X mostraron que la cristalinidad aumentó con el tiempo de almacenamiento, incrementándose la rigidez, y disminuyendo el brillo de los films. Del mismo modo, la cristalinidad afectó a la capacidad de sorción de agua de los films en función de la humedad relativa y la temperatura. La temperatura de transición vítrea de los films de almidón se vio afectada por la adición de ácidos grasos saturados pero no por la adición de ácido oleico. La presencia de dichos componentes promovió la formación de estructuras cristalinas tipo V, indicando la formación de complejos entre los lípidos y las cadenas de amilosa e inhibiendo la formación de otros tipos de formas cristalinas. Se analizó también el efecto de la incorporación de otros biopolímeros en la posible mejora de la funcionalidad de los films de almidón. En las mezclas con hidroxipropilmetilcelulosa (HPMC), se inhibió la retrogradación del almidón en los films composite, pero se observó un efecto negativo en las propiedades barrera de los mismos, que fueron más permeables, principalmente al oxígeno. La adición de HPMC produjo separación de fases en los films (observada por microscopía electrónica de barrido). Por el contrario, la incorporación de caseinato de sodio (NaCas) permitió formar films homogéneos y menos permeables al oxígeno. Los films presentaron una resistencia mecánica algo menor que los films de almidón puro pero una mayor flexibilidad sin incrementar los valores de permeabilidad al vapor de agua. La reorganización de las cadenas de los polímeros con el tiempo de almacenamiento provocó la disminución de la resistencia mecánica, la deformabilidad y el brillo de los films composite. Atendiendo a los efectos observados, se eligió como formulación más adecuada el film composite formado por almidón y NaCas con un ratio de polímeros del 50:50. El film composite de almidón y NaCas (50:50) se estudió como matriz para la incorporación de compuestos bioactivos como son el ¿-tocoferol y el aceite esencial de naranja o su principal componente, el D-limoneno. El efecto de la adición de ¿-tocoferol se comparó con la influencia de la adición de ácido oleico y también con la adición de ambos compuestos. La adición de lípidos provocó una separación de fases entre el almidón y el NaCas debido a la diferente interacción entre cada polímero y los lípidos. Asimismo la adición de ácido oleico incrementó significativamente la permeabilidad al oxígeno, al contrario que el ¿-tocoferol, que además impartió a los films una elevada capacidad antioxidante. La incorporación de aceite esencial de naranja y D-limoneno se realizó utilizando nanoliposomas de lecitina de soja y lecitina de colza que encapsularon los compuestos activos. La incorporación de nanoliposomas en los films se realizó directamente en las dispersiones acuosas sin posterior homogeneización para evitar su ruptura. La adición de los compuestos bioactivos en forma de nanoliposomas no confirió capacidad antimicrobiana a los films, salvo en el caso de los nanoliposomas de lecitina de soja con aceite esencial, debido probablemente a la dificultad de los compuestos encapsulados para difundir en el film por la gran estabilidad de los liposomas y a la baja actividad antilisteria del D-limoneno y el aceite esencial de naranja. / Jiménez Marco, A. (2013). Propiedades de films de almidón de maíz. Influencia de la incorporación de lípidos, biopolímeros y compuestos bioactivos [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/28214 / Premios Extraordinarios de tesis doctorales

High Performance Liquid Chromatography (HPLC) is a widely used tech-nique both for detecting and purifying substances in academy and in the industry. In order to facilitate the use of, and knowledge in HPLC, character-ization of stationary phases is of utmost importance. Tailor made characteri-zation methods and workflows are steadily increasing the speed and accura-cy in which new separation systems and methods are developed. In the field fundamental separation science and of preparative chromatography there is always the need for faster and more accurate methods of adsorption isotherm determination. Some of that demand are met with the steadily increase of computational power, but the practical aspects on models and methods must also be further developed. These nonlinear characterization methods will not only give models capable of describing the adsorption isotherm but also actual values of local adsorption energies and monolayer saturation capacity of an individual interaction sites etc.The studies presented in this thesis use modern alkali stable stationary phas-es as a model phase, which will give an insight in hybrid materials and their separation mechanism. This thesis will include an update and expansion in using the Elution by Characteristic Points (ECP) method for determination of adsorption isotherms. The precision is even further increased due to the ability to use slope data as well as an increase in usability by assigning a set of guidance rules to be applied when determine adsorption isotherms having inflection points. This thesis will further provide the reader with information about stationary phase characterization and the power of using existing tech-niques; combine them with each other, and also what the expansion of meth-ods can revile in terms of precision and increased usability. A more holistic view of what benefits that comes with combining a non-linear characteriza-tion of a stationary phase with more common linear characterization meth-ods are presented.