Determination of vacuum and air drying characteristics of celeriac slices

Abstract

Celeriac slices (Apium graveolens L. var. rapaceum) weighing 100 g with moisture of 14.39 on a dry basis (kg[H2O].kg-1[DM]) were dried using vacuum drying. Drying was continued until leaf moisture fell to 0.1 on a dry basis (kg[H2O].kg-1[DM]). Six different pressures (0.1, 3, 7, 10, 13 and 17 kPa) and three different temperatures (55, 65, and 75°C) were used in the vacuum drying process. Air drying experiments were carried out at three different temperatures, 55, 65, and 75°C. In this study, measured values were compared with predicted values obtained from Page’s semi-empirical equation. The drying periods lasted 70-300 and 220-340 minutes for vacuum and air drying, respectively. Energy consumption was 1.01-2.00 and 0.84 -1.07 kWh for vacuum and air drying, respectively. Vacuum drying at 0.1 kPa and 75°C provided the optimal results with respect to drying period, colour, and energy consumption.