Microwave, convective, and intermittent microwave–convective drying of pulsed vacuum osmodehydrated pumpkin slices

Abstract

The drying of pumpkin slices (Cucurbita moschata Duch.) by microwave, convective, and intermittent microwave–convective techniques was studied. The samples were pretreated by blanching followed by pulsed vacuum osmotic dehydration. The microwave output power was 780 W. Air temperatures were 30 °C and 60 °C and air velocities were 2.22 and 4.44 m s−1. The final moisture content was set at 0.08 kg [H2O] kg−1 [dry matter]. The drying kinetics were obtained and fitted with the Fick's model and the Page's empirical correlation. Color, water activity, shrinkage, and rehydration were evaluated. Shorter drying times, higher diffusivity and better color quality were obtained by employing microwave. Convective experiments carried out to higher water activity and lower shrinkage. For describing the drying behavior, the better adjustment was reached by the Page's empirical correlation.