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Etude des migrations de l'eau et du chlorure de sodium dans des gels alimentaires : influence de la composition du gel et du procédé appliqué

Abstract : Three experimental devices (joined cylinders, dry salting and a drying cell) were used to generate moisture and sodium chloride (NaCl) profiles in gels (gelatin, different starch/gelatin ratios) maintained at constant temperature (10 and 20°C). The moisture and chloride concentrations profiles were measured by a destructive method (slicing: 1 and 5 mm of thickness / analysis of moisture (oven) and chloride (potentiometric titration)). A drying cell was set up in order to generate salt and moisture gradients in salt added gelatin gels maintained at constant temperature and to obtain a large range of moisture fluxes (from 0,00003 to 0,0003 kg water per square meter and per second). For those investigated moisture fluxes, binary diffusion of moisture and chlorides seems to be the predominant phenomenon. Apparent diffusivities were either estimated by applying a direct data treatment method to measured profiles or identified by using a mathematical model taking the retraction of the gel into account. The direct data treatment method does not require any assumption on the D=f(X) relation. It can be applied to profiles with relatively few measurements - approximately 10 - when smoothing the experimental points by using a neural network. The two methods provided similar estimations of apparent moisture and chlorides diffusivities. The values depend neither on the strengh of gelatin gels (Bloom) nor on the anhydrous composition of the gel (ratio starch/gelatin). Apparent chloride diffusitivity is relatively constant and lower than mutual salt-water diffusivity. Apparent moisture diffusitivity decreases with moisture content when measured on gels during dehydration but, increases with decreasing moisture content in the gels during re-hydration. The addition of sodium chloride causes an increase of the apparent moisture diffusivity by a factor 10.
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Submitted on : Monday, June 2, 2008 - 8:00:00 AM
Last modification on : Friday, August 5, 2022 - 2:54:00 PM
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  • HAL Id : pastel-00003704, version 1
  • PRODINRA : 246680


Nourhène Boudhrioua. Etude des migrations de l'eau et du chlorure de sodium dans des gels alimentaires : influence de la composition du gel et du procédé appliqué. Sciences de l'ingénieur [physics]. ENSIA (AgroParisTech), 2004. Français. ⟨NNT : 2004EIAA0136⟩. ⟨pastel-00003704⟩



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