Mass transfer dehydration mechanisms

The above picture of the mechanism of osmotic dehydration suggests that the plasma lemma resistance to mass transfer affects the process to only a small extent. The process will be rather dependent on the internal resistance to osmotic flow and apoplast dewatering and, to some extent, on external resistance to mass transfer. 

The models based on the irreversible process thermodynamics show that the cell membrane (plasma lemma) represents the major resistance to mass transfer. This is contradicted by findings of Raoult-Wack et al. [46-48], who showed that membranes are not necessary for osmotic dehydration and merely diffusive properties of the material are responsible for high water flux with only marginal sugar penetration. These authors suggest the following mechanism. 

The role of intercellular space and capillary flow in osmotic dehydration was well documented by Hto et al. [51-53]. On this basis the nondiffusional mass transfer model was developed incorporating hydrodynamic mechanism (HDM). Studies done by the same group [19,54] showed that long time of osmotic process is needed to obtain a fully developed water and sugar concentration profiles. A model based on the advancing disturbance front (ADF) was proposed that allows prediction of sample concentration during osmotic dehydration. 

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