INFLUENCE OF ULTRASOUND PRETREATMENT ON CONVECTIVE DRYING OF PINEAPPLE

The convective drying is a slow operation. Several techniques has been studied to increase the kinetics of process such as the pretreatments in liquids or the application of high intensity ultrasound during both, pretreatment or convective drying. In this work, the influence of the pretreatment (with distilled water (20 and 40 min at 25 °C) on convective drying (40 °C, 1 m s) of pineapple slices (2.0 cm diameter, 0.5 cm thickness) was studied. The application of ultrasound during pretreatment (55.5 W/L, 40 kHz) or during convective drying (31 kW m; 21.8 kHz) was also addressed. The results showed that the application of ultrasound during the pretreatment and during drying increased water transport and reduced the drying time. The use of ultrasound in the pretreatment or in the convective drying could improve drying processes.