Air drying characteristics and moisture diffusivity of carrots

The effects of air temperature on drying kinetics of carrot cubes were investigated. Convective drying characteristics of carrot cubes in a spout-fluidized bed were evaluated through the effect of air temperature on drying kinetics. Drying was carried out at 60, 70,80 and 90 C and the falling drying rate data were used to calculate the effective diffusion coefficients from the Fick's equation. Four mathematical models available in the literature were fitted to the experimental data. The Two-term model is given better prediction than the Henderson and Pabis, Page and Lewis model and satisfactorily described drying characteristics of carrot cubes. Two different models were applied to describe moisture diffusivity in carrots. Both consider the changes in temperature and moisture content of carrots during drying as well as account for or neglect the material shrinkage which was the parameter diversifying the models. It was confirmed that shrinkage should be accounted for to attain reliable values of effective moisture diffusivity in carrots. It was observed that if shrinkage phenomena are not taken into consideration during modeling of drying kinetics, then the effective moisture diffusivity in carrots is underestimated at the initial phase of drying and is overestimated at the final drying phase. (C) 2009 Elsevier B.V. All rights reserved.