Influence of ohmic heating and vacuum impregnation on the osmotic dehydration kinetics and microstructure of pears (cv. Packham's Triumph)

The effect of ohmic heating (OH) and vacuum impregnation (VI) on the osmotic dehydration kinetics and microstructure of pears was studied. Three different dehydration levels (30, 40 and 50 C) were used, by applying VI or not (OD) and OH (100 V). Dehydrated samples showed that the application of OH during the osmotic treatments had significant effects on the kinetics of water loss and sugar gain as well as on the microstructure of samples. The greatest water loss was observed with the OD-OH. The largest amount of solute gain and the smallest firmness loss were obtained in the VI-OH. In some treatments, the process time was reduced by as much as 40%. The SEM observations showed that cell deformation and cell rupture were significant in the OD-OH than on the VI-OH samples. The increases in the permeability of cell by OH explain the acceleration of mass transference and process time reduction. (C) 2011 Elsevier Ltd. All rights reserved.