The drying characteristics of “Granny Smith” apple were investigated using a bench-scale fluidised bed drier at different temperatures and using blanching in hot water as pre treatment. Temperatures of fluidisation for non-treated and treated samples were 50, 60, 70 and 80 oC and airflow velocity 3.50 m s-1. The aim of the experiment was to get apples with approximately 9% water content, with good texture, rehydration capability and colour quality. The effect of temperatures and pre-treatment on the quality of dried apple samples was determined on the basis of colour and volume changes and reconstitution characteristics. Th e kinetic equations were estimated using logarithmic model. The results of the estimation have exhibited correspondence to experimental results. As a result of drying of non-treated apple at higher temperatures, drying time shortens, while rehydration properties improve. On the other hand, with the increase of the drying temperature, overall colour changes (ΔE) of non-treated samples increase. The best results, shorter drying time and better rehydration properties, were obtained when samples were pre-treated by blanching in hot water.

fluid bed dryer; Granny Smith apple; drying kinetics; pre-treatment; blanching; rehydration

Published by University of Zagreb, Faculty of Agriculture, Zagreb, CROATIA
Sponsored by Ministry Science and Education of the Republic of Croatia