Modeling convective thin-layer drying of carrot slices and quality parameters

Abstract

The influence of thin layer convective dehydration parameters on drying kinetics parameters, chemical composition, and color parameters of carrot slices were investigated, and corresponding mathematical models were developed. In the carrot slices, convective dehydration process hot air temperature and the sample slice thickness were varied, while measured, calculated, and modeled responses were: time of dehydration, effective moisture diffusivity, the energy of activation, proteins and cellulose contents, lightness, redness, and yellowness. The obtained results showed that varied convective dehydration process parameters statistically significantly affected all investigated responses except activation energy. The most efficient drying model with the minimum thickness (3 mm) and the maximum drying temperature (70 ?C) had the shortest drying time (231 min). This model had the minimum resistance to mass transfer (the minimum effective moisture diffusivity, 2.04?10-08 - 7.12?10-08 [m2s-1]), and the average maximum energy of activation (31.31 kJmol-1). As far as the carrot slices' chemical composition and color parameters were concerned, the model with the maximum thickness (9 mm) and the minimum drying temperature (35 ?C) was the optimal one. This model had the longest dehydration time (934 min), the maximum resistance to the mass transfer (8.87?10-08 [m2s-1]), the minimum total protein content (5.26 %), and the darkest color (49.70). The highest protein content (7.91%) was found for the samples subjected to the highest drying temperatures and the lowest carrot slice thickness. In contrast, the process of convective dehydration had led to the lighter, reddish, and yellowish carrot slices. All developed mathematical models were statistically significant.