DRYING OF ONION - EFFECTS OF PRETREATMENT ON MOISTURE TRANSPORT

This study investigated the drying of osmosed and fresh onions. Onion slices (0.8 x 0.8 x 0.15 cm) soaked in sodium chloride solutions (10 a nd 15% w/w) for 60 min at 22 degrees C were submitted to air drying. T he experimental kinetics data obtained were employed to determine effe ctive diffusivity, using a mass transfer model based on Fick's law of diffusion applied to thin slabs. The results show those samples soaked in the 10% NaCl solution had faster drying rates and larger moisture diffusion coefficients. The drying time of onions can be reduced to le ss than half by introducing an hour of osmotic dehydration in a salt s olution. The dried previously osmosed samples presented a more natural coloration than the untreated ones did.