Investigation of ultrasound-assisted convective drying process on quality characteristics and drying kinetics of zucchini slices

Abstract

In the present investigation, the ultrasound-assisted convective drying process for zucchini slices was studied. In this regard, the effects of convective air velocity (in three levels of 1, 2, and 3 m/s) and ultrasonic pretreatment time (in three levels of 0, 15, and 30 min) on drying kinetic, drying time, and qualitative characteristics of the dried product were investigated. Moreover, the effects of these independent variables on functional groups of dried zucchini slices were also studied using Fourier Transform Infrared spectroscopy (FTIR), and those on the microscopic structure of dried zucchini slices were investigated using Scanning Electron Microscopy (SEM). Based on the results obtained in this study, the ultrasonic pretreatment for 30 min and convective air velocity of 2 m/s are recommended for drying zucchini slices with optimal product quality and short drying time. Compared to untreated samples, less wrinkled tissues and more microscopic channels were observed in pretreated samples especially at 30 min sonication time. In terms of functional groups, there was no difference in the FTIR spectra at different levels of ultrasonic pretreatment time and convective air velocity.