Desorption isotherms and drying characteristics of carrot using tray and heat pump-assisted dehumidified drying

Abstract

Desorption isotherms of sliced carrots have been measured. A non-linear regression program was applied to the experimental data to fit with any of the four moisture sorption isotherm models. The Modified Chung-Pfost and Modified Henderson showed the best fit to both the function RHe = f (Xe ,T) and Xe = f (RHe , T), respectively. Sliced carrots were pretreated by blanching prior to drying at three temperatures of 40, 50 and 60  C in tray and heat pump-dehumidified dryers. The drying data were fitted to the Modified Page model. The drying constant was related to air temperature using Arrhenius model. Effective moisture diffusivities were determined using the drying data. Heat pump-dehumidified drying and blanching reduced drying times. Quality evaluation by color values, rehydration ratio and β - carotene content showed the best quality for sliced carrots pretreated by blanching and dried at 40 C in the heat pump-dehumidified dryer.