Study of the Drying Kinetics of “Granny Smith” Apple in Fluid Bed Dryer

Th e drying characteristics of “Granny Smith” apple were investigated using a bench-scale fl uidised bed drier at diff erent temperatures and using blanching in hot water as pre-treatment. Temperatures of fl uidisation for non-treated and treated samples were 50, 60, 70 and 80 oC and airfl ow velocity 3.50 m s-1. Th e aim of the experiment was to get apples with approximately 9% water content, with good texture, rehydration capability and colour quality. Th e eff ect 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. Th e 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. Th e best results, shorter drying time and better rehydration properties, were obtained when samples were pre-treated by blanching in hot water.