Effect of ultrasound assisted vacuum osmotic dehydration on the mass transfer kinetics and qualities of orange slices

Abstract

This research aimed to explore the effects of combined ultrasound and vacuum assisted osmotic dehydration on the mass transfer kinetics and qualities of fresh-cut orange slices. The experiments were carried out under four different conditions, i.e., osmotic dehydration (OD), vacuum osmotic dehydration (VOD), ultrasound assisted osmotic dehydration (UOD) and ultrasound assisted vacuum osmotic dehydration (UVOD). Aqueous solutions of the four osmotic agents – sucrose, xylitol, sorbitol, and maltitol at a concentration of 50°Brix were used in each condition. The results showed that UVOD had the highest (p < 0.05) water loss (WL) and solid gain (SG). The high regression coefficient (R2 > 0.99) and low χ2 and RMSE values revealed the applicability of Peleg model for fitting mass transfer of orange slice during osmotic dehydration. Low-field nuclear magnetic resonance (LF-NMR) spectra revealed the water distribution in orange cells. Electronic nose data indicated that osmotic dehydration did not significantly (p > 0.05) change the flavor of orange slices. Fourier transform infrared (FTIR) spectra indicated osmotic dehydration could preserve internal chemical composition of orange slice. Scanning electron microscope (SEM) images illustrated the mechanisms of VOD, UOD and UVOD. The results of mass transfer kinetics and qualities showed that sugar alcohols were good alternative osmotic agents to sucrose. Although UVOD led to the largest loss of vitamin C due to its highest WL, UVOD exhibited better hardness and could combine the advantages of VOD and UOD in water activity and color, respectively.