Effect of two stage, tray and heat pump assisted-dehumidified drying on drying characteristics and qualities of dried ginger

Desorption isotherms for sliced gingers have been measured. A non-linear regression programme was used to fit four moisture sorption isotherm models to the experimental data. The Modified Halsey and Modified Oswin models gave the best fit for X-e = f(RHe, T) and RHe = f(X-e, T), respectively. Tray and heat pump dehumidified drying incorporated by single and two stage drying were conducted. It was found that the modified Page model was the most effective. The drying constant was fitted to drying air temperature using the Arrhenius model. Effective moisture diffusivities were determined using the drying data. The heat pump dehumidified drying incorporated by the two stage drying could reduce the drying time at 40 degrees C by 59.32% and increase 6-gingerol content by 6%. Quality evaluation by 6-gingerol content, rehydration ratio and Delta E* showed the best quality for dried sliced gingers in the heat pump dehumidified drying incorporated by the two stage drying at 40 degrees C. (C) 2010 The Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.