STRUCTURAL CHANGE KINETICS IN OSMOTIC DEHYDRATION OF APPLE TISSUE

摘要

Volume changes which occurred in apple slices (1 cm thick) throughout (7 h)rnosmotic dehydration with 65% w/w sucrose solution at 30, 40 and 50 oC have beenrnanalyzed. Osmotic treatments were carried out at atmospheric pressure (OD) and byrnapplying a vacuum pulse at the beginning of the process (PVOD). Sample volumernchanges were related with those of each one of the phases (solid matrix, fruit liquidrnphase and gas phase) which can be considered in an idealized porous fruit structure. Thernvolume of the fruit liquid phase and its change throughout process were estimated fromrnsample composition (water and soluble solids) before and after treatment. Changes inrnthe volume of fruit solid matrix can be considered negligible due to its small initialrnvolume. So, the changes in the gas phase volume in each case can be estimated from thernvolume balances. Volumes of water lost and solute gained greatly contributed tornexplaining sample volume loss. The higher the solute gains, the smaller the samplernvolume loss. Nevertheless, in porous fruits, changes in the gas phase volume also playrnan important role, even when a great part of the initial gas is removed by applying arnvacuum pulse. Changes in the sample porosity occurred in line with dehydration.