Moisture loss kinetics and microstructural changes in eggplant (Solanum melongena L.) during conventional and ultrasonically assisted convective drying

The overall aim of this study was to assess the moisture loss kinetics and the structural changes induced by both conventional and ultrasonically assisted convective drying of eggplant tissue. Three sets of drying experiments (at 40 degrees C and 1 m/s) were carried out: conventional air drying and ultrasonically assisted drying at two different levels of applied ultrasonic power, 45 and 90 W. The microstructure of the dried samples was studied by scanning electron microscopy. The application of ultrasound during the convective drying of eggplant led to a significant reduction of the drying time. The ultrasonic effect was dependent on the power applied, thus, the higher the power, the faster the moisture loss. The microstructure of eggplant endocarp was greatly affected during conventional air drying, probably due to the long drying times. This microstructure was better preserved after the application of a moderate ultrasonic power (45 W), due to the shorter drying time and the mild mechanical effects of ultrasound on the endocarp cells. (C) 2012 The Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.