ULTRASOUND PRE-TREATMENT APPROACH: CONVECTIVE DRYING OF CARROT

Abstract

In this study, carrot samples that have different slice thicknesses (2 and 4 mm) were dried by applying ultrasound pre-treatment at different time periods (0, 20 and 40 min) and the changes in colour, rehydration, pH and °Brix values were examined. Besides, microstructures of dried samples under different conditions were observed through scanning electron microscopy images. Drying was carried out in a modified oven at temperatures of 60 and 70 °C with an air velocity of 1 m/s. A decrease in b*(green/red) values was observed due to the effect of drying. The highest rehydration ratio (6.930) was found in 2 mm thick carrot samples, which were dried at 60 °C and treated with ultrasound for 40 minutes. It was observed that pH and °Brix values changed from 6.705 to 6.120 and from 68.70 to 6.80, respectively. An increase in the change of product structure was observed as a consequence of the increasing duration of ultrasound pre-treatment. It was emphasized that ultrasound technology might be the appropriate method for drying the carrot sample.