Investigation of potato drying kinetics and quality parameters applying ultrasound pre-treatment

Abstract

In this study, the effect of ultrasound pre-treatment on quality parameters (colour, rehydration, pH and degrees Brix) of potato samples was investigated. In addition, the drying kinetics of the potato samples was evaluated and ten different thin-layer mathematical models were fitted to experimental data to select the best model for the drying processes. Two different slices of potato samples (2 and 4 mm) were ultrasound pre-treated for 0, 20 and 40 min before drying. Drying was carried out in a modified oven at 60 and 70 degrees C at an air velocity of 1 m/s. As the ultrasound pre-treatment time applied to the samples increased, the drying time of the product decreased. Drying rate decreased with increasing product slice thickness. When compared to fresh potatoes, a decrease in yellowing values (b*) was observed for the different drying conditions employed. Rehydration ratio values under all conditions ranged from 2.856 to 2.640. Potato samples with a thickness of 4 mm, dried at 60 degrees C without ultra-sound pre-treatment, presented the highest pH value. The potato samples of 2 mm thick-ness, dried at 70 degrees C and treated with ultrasound for 40 min, showed the content of water-soluble solids (degrees Brix) closest to the fresh product. The results showed that the pre-treatment by ultrasound can be used as an alternative method for drying potato with hot air.