STUDIES ON THE EFFECT OF SURFACTANT, BLANCHING AND OSMOTIC PRETREATMENTS ON THE CONVECTIVE DRYING OF POTATOES

Moisture removal from solids is an integral part of food processing. To approach the drying process of a given product it is necessary to have a knowledge of the drying kinetics. However, foodstuffs are often subjected to certain chemical and physical treatments, such as surfactant impregnation, osmotic dehydration or blanching, prior to convective drying. The drying behavior of potatoes was monitored within an experimental air tunnel dryer, with the mechanism of internal moisture migration being identified as diffusion. This was subsequently evaluated on the basis of the liquid diffusion theory. Experimental data revealed osmotic concentration as a favorable process. A 29±2% reduction in diffusion coefficient was observed following osmotic dehydration with a salt/sugar solution, however, this provided a 63±3% reduction in drying time. Structural modifications were induced by blanching, with this rendering a 10±1 and 27±2% lowering of the moisture transfer rate during drying at 30 and 60C, respectively.