Kinetics of vacuum drying of pumpkin (Cucurbita maxima):: Modeling with shrinkage

The drying kinetics of pumpkin (Cucurbita maxima) in nature and pre-treated by freezing and blanching was studied by using a vacuum dryer. The experimental runs were driven at pressures of 5-25 kPa and temperatures of 50-70 degrees C. It was observed that the applied pre-treatment influence favorably in the kinetic of drying, however freezing showed greater influence than blanching. It was observed that the best values were obtained. for the highest temperature and lowest pressure for the samples pre-treated by freezing. The experimental curves of drying were adjusted to the diffusional model of Fick for an infinite slab with and without shrinkage. The values of effective diffusivity obtained by considering the samples shrinkage were smaller than those calculated without considering this phenomenon. (c) 2005 Elsevier Ltd. All rights reserved.