Convective hot airdrying characteristics of selected vegetables

Abstract

The objectives of the present work were to investigate and to model the convective hot air-drying characteristics of carrot, zucchini and eggplant at different drying air temperatures (60, 70 and 80 oC). Drying characteristics were determined by the plot of moisture loss of samples versus drying time in 10 min intervals for each drying air temperatures. The experimental moisture data were then fitted to selected thin layer drying models available in the literature, namely Henderson and Pabis, Newton and the two-term models and good agreements between experimental and predicted values of moisture contents were observed (R2>0.98). Results showed that all drying took place in falling rate period for all samples at all drying air temperatures studied. Increase in drying air temperature from 60 oC to 80 oC resulted in a decrease of total drying time 35%, 45% and 50% for carrot, zucchini and eggplant respectively. Drying rate constants (a, b, k, k0 and k1) increased with the increasing drying air temperature. Comparison between experimental and predicted values of moisture content versus drying air temperature indicated that the most suitable models for carrot, zucchini and eggplant drying were two-term, Henderson and Pabis and Newton respectively at 60 oC, two-term, Henderson and Pabis and Newton model at 70 oC and two-term, Henderson and Pabis and Newton model at 80 oC drying air temperature respectively.