Transport Mechanisms in Osmotic Dehydration: The Role of the Structure

2003 ◽  
Vol 9 (3) ◽  
pp. 179-186 ◽  
Author(s):  
A. Chiralt ◽  
P. Fito
Keyword(s):  
Mass Transfer ◽  
Mass Transport ◽  
Atmospheric Pressure ◽  
Osmotic Dehydration ◽  
External Solution ◽  
Bulk Flow ◽  
Solute Diffusion ◽  
Structural Level ◽  
Intercellular Spaces ◽  
Water Release

Osmotic dehydration promotes water release from a cellular material immersed in a concentrated solution, while a simultaneous external solute uptake happens. Mass transfer occurs during this operation through different mechanisms to a different extent depending on process variables. The action of the different mechanisms, balanced by controlling those variables, makes possible to achieve a specific dewateringsolute uptake ratio in the final product. Mechanisms involved in mass transfer during osmodehydration of cellular tissues depend on the structural level of the tissue. The external broken cells can be easily impregnated by the external solution, and in the intercellular spaces, bulk flow of solution, water and solute diffusion occur. The bulk flow is promoted due to capillary pressure in processes carried out at atmospheric pressure. Nevertheless, when vacuum is applied to the system, capillary impregnation is promoted and when the atmospheric pressure is restored, pores are extensively flooded with the external solution and depending on the applied compression ratio. Mass transport in the intercellular spaces is mainly responsible for solute gain. At cellular level, cell wall and membranes act as non-selective and selective barriers respectively to mass transport and the transmembrane flux is responsible for most of the cell-to-cell water transport during osmotic dehydration of tissues.

scholarly journals Mathematical modelling of the osmotic dehydration of physalis

2018 ◽  
Vol 21 (0) ◽  
Author(s):  
Fernanda Rosa Assis ◽  
Rui Manuel Santos Costa de Morais ◽  
Alcina Maria Miranda Bernardo de Morais
Keyword(s):  
Mass Transfer ◽  
Atmospheric Pressure ◽  
Osmotic Dehydration ◽  
Mass Ratio ◽  
Promising Alternative ◽  
Sucrose Solutions ◽  
Mass Transfer Kinetics ◽  
Osmotic Agent ◽  
Effective Diffusivities ◽  
Best Fit

Abstract Physalis was osmotically dehydrated with 60 °Bx sucrose or sorbitol solutions at 60 °C and with a mass ratio of sample to solution of 1:4, at atmospheric pressure or under vacuum at 150 mbar. The Crank’s, Peleg’s and Page’s models were tested to describe the mass transfer kinetics for water loss (WL) and solids gain (SG). The effective diffusivities of both water and solute were around 10-11 m2 s-1 under all conditions. Peleg’s model presented the best fit. The use of sorbitol as the osmotic agent resulted in an increase in the WL rate. In experiments with sucrose solutions, a higher WL was obtained under vacuum than at atmospheric pressure. The SG was particularly low during osmotic dehydration. Thus, the use of sorbitol as the osmotic agent was shown to be a promising alternative to sucrose.

Effect of Blanching and Vacuum Pulse Application on Osmotic Dehydration of Pear

2003 ◽  
Vol 9 (5) ◽  
pp. 321-328 ◽  
Author(s):  
M. Chafer ◽  
C. Gonzalez-Martinez ◽  
B. Fernandez ◽  
L. Perez ◽  
A. Chiralt
Keyword(s):  
Water Loss ◽  
Atmospheric Pressure ◽  
Transfer Rate ◽  
Osmotic Dehydration ◽  
Mass Transfer Rate ◽  
Structural Response ◽  
External Solution ◽  
Gas Release ◽  
Volume Compression ◽  
Pre Treatment

Osmotic dehydration of pear cylinders (var. blanquilla) was studied by analysing the effect of blanching pre-treatment and the application of a vacuum pulse on the kinetics and yield of the process and on product quality (colour and mechanical behaviour). Fresh and stem-blanched samples were treated with 65 Brix sucrose at atmospheric pressure and by applying a vacuum pulse (50 mbar for 5 min). The influence of the sugar gain and water loss fluxes, and the tissue structural response to the vacuum pulse, on the total mass and volume losses of the samples has been discussed. Blanching implied an increase in the mass transfer rate in pear tissue. Vacuum pulse in blanched samples resulted in more volume compression than sample impregnation with the external solution due to the sample softening by thermal effect and to the partial gas release during its thermal expansion. This provoked the greatest volume losses and a reductionof the ratio of sugar gain to water loss, where the highest values reached were for non-blanched samples submitted to vacuum pulse. Mechanical changes induced by treatments were similar inall cases, but colour hue and chrome were better preserved in samples treated by PVOD. Nevertheless, this treatment implied a transparency gain due to the sample gas release and so, samples become darker.

scholarly journals Vacuum-Assisted Osmotic Dehydration of Autumn Olive Berries: Modeling of Mass Transfer Kinetics and Quality Assessment

Foods ◽  
2021 ◽  
Vol 10 (10) ◽  
pp. 2286
Author(s):  
Mohamed Ghellam ◽  
Oscar Zannou ◽  
Charis M. Galanakis ◽  
Turki M. S. Aldawoud ◽  
Salam A. Ibrahim ◽  
...  
Keyword(s):  
Mass Transfer ◽  
Water Loss ◽  
Atmospheric Pressure ◽  
Sucrose Solution ◽  
Osmotic Dehydration ◽  
Vacuum System ◽  
Pressure System ◽  
Solid Gain ◽  
Autumn Olive ◽  
Mass Transfer Kinetics

Autumn olive fruits were osmo-dehydrated in sucrose solution at 70 °C under vacuum and atmospheric pressure. The mass transfer kinetics data were applied to the models of Azuara, Crank, Page, and Peleg. The Peleg model was the best-fitted model to predict the water loss and solid gain of both treatments. The vacuum application decreased the effective diffusivities from 2.19 × 10−10 to 1.55 × 10−10 m2·s−1 for water loss and from 0.72 × 10−10 to 0.62 × 10−10 m2·s−1 for sugar gain. During the osmotic dehydration processes, the water activity decreased and stabilized after 5 h, while the bulk densities increased from 1.04 × 103 to 1.26 × 103 kg/m3. Titratable acidity gradually reduced from 1.14 to 0.31% in the atmospheric pressure system and from 1.14 to 0.51% in the vacuum system. pH increased significantly in both systems. Good retention of lycopene was observed even after 10 h of treatments. For the color parameters, the lightness decreased and stabilized after 30 min. In comparison, the redness and yellowness increased in the first 30 min and gradually decreased towards the initial levels in the fresh fruit.

scholarly journals Osmotic dehydration of carrot in sugar beet molasses: Mass transfer kinetics

2010 ◽  
pp. 47-55
Author(s):  
Gordana Koprivica ◽  
Nevena Misljenovic ◽  
Ljubinko Levic ◽  
Lidija Jevric ◽  
Bojana Filipcev
Keyword(s):  
Mass Transfer ◽  
Sugar Beet ◽  
Atmospheric Pressure ◽  
Immersion Time ◽  
Osmotic Dehydration ◽  
Maximal Effect ◽  
Beet Molasses ◽  
Working Temperature ◽  
Sugar Beet Molasses ◽  
Mass Transfer Kinetics

The osmotic dehydration process of carrot in sugar beet molasses solutions (40, 60 and 80%), at three temperatures (45, 55 and 65?C) and atmospheric pressure, was studied. The main aim was to investigate the effects of immersion time, working temperature and molasses concentration on mass transfer kinetics during osmotic dehydration. The most important kinetic parameters were determined after 20, 40, 60, 90, 120, 180, 240 and 300 min of dehydration. Diffusion of water and solute was the most intensive during the first hour of the process and the maximal effect was observed during the first 3 hours of immersion. During the next two hours of dehydration, the process stagnated, which implied that the dehydration time can be limited to 3 hours.

Laboratory Experiments of Mass Transfer in the London Clay

1988 ◽  
Vol 127 ◽  
Author(s):  
P. J. Bourke ◽  
D. Gilling ◽  
N. L. Jefferies ◽  
D. A. Lever ◽  
T. R. Lineham
Keyword(s):  
Mass Transfer ◽  
Porous Media ◽  
Radioactive Waste ◽  
Mass Transport ◽  
Mathematical Models ◽  
Laboratory Experiments ◽  
Naturally Occurring ◽  
Diffusion And Convection ◽  
Waste Repository ◽  
London Clay

ABSTRACTAqueous phase mass transfer through the rocks surrounding a radioactive waste repository will take place by diffusion and convection. This paper presents a comprehensive set of measurements of the mass transfer characteristics for a single, naturally occurring, clay. These data have been compared with the results predicted by mathematical models of mass transport in porous media, in order to build confidence in these models.

Mass Transfer Modeling and Shrinkage Consideration during Osmotic Dehydration of Fruits and Vegetables

2011 ◽  
Vol 27 (4) ◽  
pp. 331-356 ◽  
Author(s):  
Hilaire Nahimana ◽  
Min Zhang ◽  
Arun S. Mujumdar ◽  
Zhansheng Ding
Keyword(s):  
Mass Transfer ◽  
Fruits And Vegetables ◽  
Osmotic Dehydration ◽  
Mass Transfer Modeling
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