Convective hot air drying characteristics of selected vegetables

Abstract

The objectives of the present work were to investigate and to model the convective hot air-dryingcharacteristics of carrot, zucchini and eggplant at different drying air temperatures (60, 70 and 80oC). Drying characteristics were determined by the plot of moisture loss of samples versusdrying time in 10 min intervals for each drying air temperatures. The experimental moisture datawere then fitted to selected thin layer drying models available in the literature, namelyHenderson and Pabis, Newton and the two-term models and good agreements betweenexperimental and predicted values of moisture contents were observed (R2>0.98). Resultsshowed that all drying took place in falling rate period for all samples at all drying airtemperatures studied. Increase in drying air temperature from 60 oC to 80 oC resulted in adecrease 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 airtemperature indicated that the most suitable models for carrot, zucchini and eggplant drying weretwo-term, Henderson and Pabis and Newton respectively at 60 oC, two-term, Henderson andPabis and Newton model at 70 oC and two-term, Henderson and Pabis and Newton model at 80oC drying air temperature respectively.