CONVECTIVE-AIR DRYING KINETICS OF OSMOTICALLY PRETREATED BLUEBERRIES

The second stage convective drying behavior of osmo-dehydrated blueber ries was evaluated in a forced-air cabinet dryer (temperature: 50 degr ees C, relative humidity: 14%, air velocity: 0.6 m/s) with a cross-flo w tray arrangement. Fick's second law of unsteady state diffusion was used to model the air drying kinetics. The results showed that the con vective-air drying of the blueberries occurred in two falling rate per iods. The effective diffusion coefficients, D-eff, during the first fa lling rate period ranged from 1.19 x 10(-10) m(2)/s to 2.14 x 10(-10) m(2)/s and ranged from 4.04 x 10(-11) m(2)/s to 1.32 x 10(-10) m(2)/s during the second falling rate period. Among the pre-treatment conditi ons, the temperature and sucrose concentration during osmotic dehydrat ion significantly (p < 0.05) influenced the air drying time, while the effect of contact time was not significant (p > 0.05).