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Steam-jet granulation is a process used in the dairy industry to produce instant agglomerated milk powder. The agglomerate growth process includes wetting of the particle surface, collisions of sticking particles and consolidation of the agglomerates by drying. The aim of this study was to evaluate the influence of the raw material properties (initial particle size and humidity) and processing conditions (liquid/solid ratio and post-drying conditions) on the growth mechanisms and agglomerates properties. Skim milk powders were granulated using steam-jet granulation pilot and characterized via the in-size distribution, water content, structure, thermodynamical and functional properties. The water content and the post-drying time were identified as key process parameters to control in order to obtain instant agglomerated milk powders

The most frequently used technique for dehydration of dairy products is spray drying. This is an effective method to preserve biological products as it does not involve prolong exposure of materials to severe heat treatment. Due to the variety and complexity of the concentrates to be dried, a more rigorous understanding of spray-drying based on physico-chemical and thermodynamic properties is necessary. At the same time, the current state of the art did not allow easy determination of the parameters of spray-drying of dairy products prior to drying, except from performing several complex and expensive experiments with pilot-scale spray-dryer. Nevertheless, recent advances in the understanding of product behavior toward water transfer with the development of a desorption method makes it possible to give several answers to the following question: What is the best strategy to anticipate the behavior of concentrate toward drying and to improve the process, the economy and the quality of the dairy powders?The strategical approach can be developed on the knowledge of the thermodynamic parameters of the spray dryer coupled to physico-chemical characteristics of the concentrate. The software SD2P® (Spray Drying Parameters Simulation & Determination) developed by Schuck et al. (2009) is a way, among others, to predict the value of these parameters when they are not known. The combined results provide more precise determination of spray-drying parameters (including inlet/outlet air temperature, mass/powder flow rate, powder temperature, etc.), powder state during spray-drying (stickiness) and the cost of spray-drying with respect to weather conditions. Several cases will be presented to show the interest of this strategy in order to anticipate the spray-drying parameters and the powder behavior.

Spray drying is an efficient unit operation applied in food drying that demands a high amount of energy compared to vacuum evaporation and membrane filtration. The objective of this work was to present a mathematical model-like basis for the construction of mass and energy balances. For this purpose, two lab-scale single spray dryers in milk drying with different evaporative capacities have been used as example. The values of the absolute humidity, mass and energy losses, energetic specific consumption (ESC), and the efficiency of the process were obtained by calculations developed in this work. The mathematical model was valid for the evaluation of mass and energy losses, and it allowed us to compare the efficiencies of spray dryers with different designs. From this model, it is possible to compare different drying processes and dryers.

Casein micelles (CMs) are natural supramolecular aggregates present in milk. Their structure is highly sensitive to acidification. In contrast, CMs reticulated with transglutaminase (CMs-Tg) are much more stable than CMs at acidic pH. Cyanidin-3-O-glucoside (C3G) is a water-soluble molecule of flavonoids subgroup. It shows several beneficial effects: free radical scavenging activity and prevention of cardiovascular disease. However, the low pH stability of C3G limits its applications as bioactive molecules. Its stability can be improved by binding C3G to others molecules. In this way, the objective of the present work is to investigate the interaction between CMs-Tg and C3G under acidic (pH 2.0) and neutral (pH 7.0) conditions. CMs were reticulated with Tg and then aliquoted at pH 7.0 and 2.0. ζ (Z-potential) and size of the particles of CMs-Tg were determined by dynamic light scattering (DLS). Fluorescence quenching spectroscopy was used to determine the binding interaction between CMs-Tg and C3G. Results obtained by DLS show that the average diameter of CMs-Tg was 160 ± 7 nm at pH 7.0 (similar to CMs control sample), whereas it was of 145 ± 1 nm at pH 2.0. ζ (Z-potential) of CMs-Tg was slightly more negative than of CMs (-22 mV versus -19 mV) due to the reduction of the number of positive charges on CMs consecutive to the reaction of reticulation. No difference of size and ζ was observed in the presence of C3G. Results obtained by fluorescence spectroscopy suggested that C3G quenched CMs-Tg fluorescence in a static mode with a strong binding constant of 106 M-1 at pH 7.0 and 2.0. The reticulation doesn’t affect the binding properties of CMs for C3G at pH 7.0. The various natures of interactions, obtained by thermodynamic analysis, are also considered and discussed within the present work.

The optimisation of dairy unit operations involving heat transfer requires the control of fouling and aggregation phenomena following the denaturation of thermosensitive proteins, in particular β-lactoglobulin (β-lg). This study intends to give a better view of the influence of whey components (whey proteins, lactose, and minerals such as calcium) on β-lg denaturation through a combined kinetic and thermodynamic approach. β-lg denaturation in model solutions of increasing complexity (pure β-lg solution, whey protein solution, and two model wheys differing in mineral content) was characterised at temperatures ranging from 64.5 to 98 °C by following the evolution of soluble β-lg concentration with HPLC. It was demonstrated that whatever the model solution composition, a two-step mechanism (unfolding followed by aggregation) of 1.5-order kinetics could be adopted to describe β-lg denaturation reaction, as the temperature dependence of the denaturation reaction rate was properly fitted by Arrhenius equation. The dependency of kinetic and thermodynamic parameters on solution composition indicated that the presence of whey proteins enhanced β-lg aggregation, whereas lactose showed a small protective effect against β-lg unfolding. Additionally, minerals, especially calcium, tended to stabilise β-lg native state while increasing β-lg aggregation rates. However, at high mineral content, calcium influence could be hindered or even reversed, presumably owing to a lower bioavailability due to complexation with anions such as inorganic phosphates.

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Em 2014, a produção global de leite foi 892 milhões de toneladas, tendo um aumento de 3,3% comparado a 2013. Devido à perecibilidade do leite, boa parte da produção é destinada à fabricação de produtos lácteos desidratados. Em 2014, aproximadamente 50 milhões de toneladas de leite foram destinados à produção de leite em pó integral (The World Dairy Situation, 2015). Na fabricação deste tipo de produto algumas técnicas podem ser aplicadas como “roller drying” (secagem em tambor), mas majoritariamente o “spray-drying” (secagem por atomização). Na secagem em tambor, o produto é seco por contato direto com a parede aquecida do rolo de aço inoxidável. Eles são indicados para secagem de alimentos com elevada viscosidade. Tem eficiência energética entre 300 a 1000 KWh.ton-1 de água removida, fácil operação e manutenção (WALSTRA, WOUTERS, GEURTS, 2006). Por outro lado, alguns produtos com elevados teores de açúcar podem ficar aderidos ao rolo ou apresentar sabor cozido devido ao contato direto com a superfície aquecida (JUMING, FENG, SHEN, 2003). Apesar das vantagens de ambas as técnicas, a secagem por atomização é a mais utilizada pelas indústrias de laticínios para fabricação de produtos em pó. O consumo energético deste sistema é aproximadamente um décimo do consumo da liofilização 1000 a 2000 kWh·ton-1 de água removida) e, contrariamente a técnica de secagem em tambor, os produtos não alcançam altas temperaturas durante a evaporação da água. Entretanto, essa ainda é uma das operações unitárias de maior custo energético da indústria de laticínios (SCHUCK et al., 2013; GHARSALLAOUI et al., 2007) e, por essa razão, a otimização dos parâmetros de secagem é a melhor estratégia para diminuir os gastos na produção.

In the study presented here, we investigated the interaction at pH 5.5 between folic acid (FA) and lactoferrin (LF), a positively charged protein. We found a binding constant Ka of 10(5) M(-1) and a high stoichiometry of 10 mol of FA/mol of LF. The size and charge of the complexes formed evolved during titration experiments. Increasing the ionic strength to 50 mM completely abolished the isothermal titration calorimetry (ITC) signal, suggesting the predominance of electrostatic interactions in the exothermic binding obtained. We developed a theoretical model that explains the complex triphasic ITC profile. Our results revealed a two-step mechanism: FA/LF interaction followed by self-association of the complexes thus formed. We suggest that 10 FA molecules bind to LF to form saturated reactive complexes (FA10/LF) that further self-associate into aggregates with a finite size of around 15 nm. There is thus a critical saturation degree of the protein, above which the self-association can take place. We present here the first results that provide comprehensive details of the thermodynamics of FA/LF complexation-association. Given the high stoichiometry, allowing a load of 55 mg of FA/g of LF, we suggest that FA/LF aggregates would be an effective vehicle for FA in fortified drinks.

This thesis reflects efforts toward an accurate understanding of the atomic scale structure of chalcogenide glasses. These compounds have an impact on electronics, optoelectronics and memory devices. I resorted to the most advanced first-principles molecular dynamics simulations such as the standard Car-Parrinello method as well as its second generation version. In the first part of this thesis we provide a detailed study of the topological changes undergone under pressure by glassy GeSe2 and by glassy GeSe4. Structural transition and bonding features are described and compared to the results of neutron and X-ray diffraction experiments. Furthermore, in the case of glassy GeTe4 we demonstrated that the inclusion of van der Waals forces leads to substantial improvements in the description of the structure. In the second part of this thesis, we established the atomic-scale organization of a promising candidate for phase change memory applications, glassy Ge4Sb6Te3.; Ce travail de thèse s’inscrit dans le cadre d'études théoriques ayant pour but l’établissement de la structure des chalcogénures binaires et ternaires sous différentes conditions thermodynamiques. Des techniques de modélisation numérique ab-initio ont été employées. En particulier, nous avons utilisé la dynamique moléculaire par premiers principes selon l’approche de Car et Parrinello ainsi que sa version dite "deuxième génération". La première partie est consacrée à l’étude des chalcogénures binaires, notamment les verres GeSe2 et GeSe4 sous pression ainsi qu'à l’étude des effets des forces de van der Waals et des fonctionnelles d’échange et corrélation DFT sur la structure de l’amorphe GeTe4. Dans la deuxième partie, l’intérêt a été porté à l’étude d'un matériau à changement de phase récemment proposé par les expérimentateurs comme un bon candidat pour le stockage de données, le ternaire Ga4Sb6Te3.

Serão apresentados métodos científicos e resultados tecnológicos para a realização de balanços de energia e de massa, e do calculo do tempo de retenção de uma particula no evaporador. Dando Ênfase na importância da instrumentação para o melhor controle da operação unitaria.

This study is focused on thermodynamic and mechanical properties of dense polymers solutions and related soft matter systems and conformational and rheological properties of hyperbranched polymers. Studies of hyperbranched polymers shows that they are substantially different from their linear analogs. By using simulation methods we could reach the information not available by experimental methods and hopefully obtain valuable information from both industrial and scientific points of view.This study is treating this problem by means of computer simulations where as a result we can see a hollow center for high generation numbers and a rather compact outer shell. This tendency expands to dynamical behavior. Lack of chain entanglements in hyperbranched polymers make them not very tough materials in a comparison with linear chains. Another point is a decrease of mobility caused by large amount of branch points. Viscosity loses its simple dependence on the mass as for the case of linear chains.; Ce travail était centré sur les propriétés thermodynamiques et mécaniques des polymères denses et sur leurs liens avec les systèmes de la matière molle et l'étude des propriétés de conformation et les propriétés rhéologiques des polymères hyperbranchés. L'étude de polymères hyperbranchés montre qu'ils sont substantiellement différents de leurs analogues linéaires. En utilisant des méthodes de simulation, nous pouvons obtenir des informations inaccessibles par des méthodes expérimentales et heureusement obtenir de précieuses informations du point de vue industriel et scientifique. Cette étude traite le problème par des simulations et comme expliqué dans le manuscrit, nous avons observé un centre de faible densité pour un grand nombre de générations et une enveloppe extérieure plutôt compacte. Cette tendance se retrouve également pour les propriétés dynamiques. Le manque d’enchevêtrement dans les polymères hyperbranchés fait d'eux des matériaux moins résistant que ceux composés de chaînes linéraires. La viscosité perd sa simple dépendance à la masse dans le cas d'une chaîne linéaire.

International audience; We obtained osmotic pressure data of lysozyme solutions, describing their physical states over a wide concentration range, using osmotic stress for pressures between 0.05 bar and about 40 bar and volume fractions between 0.01 and 0.61. The osmotic pressure vs. volume fraction data consist of a dilute, gas-phase regime, a transition regime with a high-compressibility plateau, and a concentrated regime where the system is nearly incompressible. The first two regimes are shifted towards a higher protein volume fraction upon decreasing the strength or the range of electrostatic interactions. We describe this shift and the overall shape of the experimental data in these two regimes through a model accounting for a steric repulsion, a short-range van der Waals attraction and a screened electrostatic repulsion. The transition is caused by crystallization, as shown by small-angle X-ray scattering. We verified that our data points correspond to thermodynamic equilibria, and thus that they consist of the reference experimental counterpart of a thermodynamic equation of state. © the Owner Societies 2016.