Effect of the Osmotic Pre-Treatment on the Convective Air Drying Kinetics of Pear Var. Blanquilla

Kinetics of air drying of fresh and osmotically pretreated pear slices was analyzed. Osmotic treatments were applied for 0.5, 3, and 48 hours in 50°Brix sucrose solutions at 30°C. Air drying was carried out at 45, 55, and 65°C, 2.2 m/s air rate. Drying curves were modelled through a Fickian equation, obtaining the effective diffusion coefficient in each case. This coefficient was markedly affected by the temperature and by the osmotic pretreatment, ranging between 6.5 × 10− 12 to 5.8 × 10 − 10 m2/s. A significant relationship between the De, and the inverse of the initial solute content of the samples was found. Activation energy of the drying process was similar for fresh and osmotically pretreated samples for 0.5 and 3 hours, but increased considerably when long osmotic treatment time was applied. Total drying time increased in osmodehydrated samples, but process yield, in terms of sample weight loss, increased. These effects were more marked when long osmotic pretreatment times were used.