Isothermal dehydration of thin films of water and sugar solutions.
The process of quasi-isothermal dehydration of thin films of pure water and aqueous sugar solutions is investigated with a dual experimental and theoretical approach. A nanoporous paper disk with a homogeneous internal structure was used as a substrate. This experimental set-up makes it possible to gather thermodynamic data under well-defined conditions, develop a numerical model, and extract needed information about the dehydration process, in particular the water activity. It is found that the temperature evolution of the pure water film is not strictly isothermal during the drying process, possibly due to the influence of water diffusion through the cellulose web of the substrate. The role of sugar is clearly detectable and its influence on the dehydration process can be identified. At the end of the drying process, trehalose molecules slow down the diffusion of water molecules through the substrate in a more pronounced way than do the glucose molecules.
Centre de Recherche sur la Matière Divisée, University of Orleans and CNRS, rue de la Férollerie 1B, 45071 Orléans Cedex 2, France.
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Heyd
Centre de Recherche sur la Matière Divisée, University of Orleans and CNRS, rue de la Férollerie 1B, 45071 Orléans Cedex 2, France.
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Rampino
Laboratory of Physical and Macromolecular Chemistry, University of Trieste, Via Giorgieri 1, 34127 Trieste, Italy.
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Bellich
Laboratory of Physical and Macromolecular Chemistry, University of Trieste, Via Giorgieri 1, 34127 Trieste, Italy.
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Elisei
Laboratory of Physical and Macromolecular Chemistry, University of Trieste, Via Giorgieri 1, 34127 Trieste, Italy.
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Cesàro
Centre de Recherche sur la Matière Divisée, University of Orleans and CNRS, rue de la Férollerie 1B, 45071 Orléans Cedex 2, France.
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Saboungi
D002482:Cellulose / Q000737:chemistry*; D003681:Dehydration; D004058:Diffusion; D005947:Glucose / Q000737:chemistry*; D012996:Solutions; D013696:Temperature; D013816:Thermodynamics; D014199:Trehalose / Q000737:chemistry*; D014867:Water / Q000737:chemistry*
D012996:Solutions; D014867:Water; D002482:Cellulose; D014199:Trehalose; D005947:Glucose