Convective drying of pumpkin: Influence of pretreatment and drying temperature

Abstract

The aim of this research was to study the influence of blanching as a pretreatment on the drying rate, color and rehydration rate of pumpkin slices (Cucurbita maxima) dried in a convective dryer at 50, 60 and 70C. The different pretreatments did not modify drying time. The diffusion coefficient depended on temperature and moisture content, but not on pretreatments. It varied between 1.6 and 2.9 × 10-9 m2/s and activation energy was approximately 35.6 kJ/mol. The rehydration rate of the dried sample, which was found to be influenced by drying temperature but not by the pretreatments, reached about 2 kg water/kg dry solid in about 150 s in boiling water. Color parameters "L" and "b" were influenced by drying temperature and pretreatments. Parameter L varied between 36 and 53 and parameter b varied between 20 and 31. Samples dried at 70C without pretreatments presented color parameter values very similar to those of the fresh sample. © 2008 Wiley Periodicals, Inc.