Effect of ultrasound on mass transfer kinetics and phenolic compounds of apple cubes during osmotic dehydration

This study investigated the impacts of ultrasound-assisted osmotic dehydration (UOD) with different frequency (40 kHz, 80 kHz, 40 + 80 kHz) and intensity (25 W/L, 50 W/L, 75 W/L) on the kinetics of mass transfer, phenolic losses and the antioxidant properties of apple cubes (8 mm). The mass transfer efficiency of solid gain (SG) was greater under dual-frequency (beta = 0.413) than 40 kHz (beta = 0.707) and 80 kHz (beta = 0.793) under the same intensity. Moreover, the mass transfer efficiency of SG under 75 W/L 40 kHz UOD was higher than that of 25 W/L and 50 W/L UOD based on beta values. Notably, the loss of phenolic content under 75 W/L UOD (18.9 %) was substantially higher than that of the 25 W/L UOD treatment (1.2-1.8 %). A UOD treatment of 50 W/L and 40 + 80 kHz is recommended to optimize mass transfer efficiency and phenolic retention of dehydrated apple cubes.