Ultrasound Assisted Osmotic Dehydration as Pretreatment for Hot-air Drying of Carrot

Abstract

Ultrasound assisted osmotic dehydration (UOD) combined hot-air drying (AD) process was investigated in this study. The influences of operation parameters such as ultrasonic energy density and solution concentration on weight reduction ratio (WRR) were discussed. The effects of UOD on the following AD of carrot slices were also studied. The results showed that ultrasonic energy density and solution concentration have positive and significant effects on WRR. Osmosis dehydration (OD) pretreatment without ultrasound assistance before AD has negative effects on the total processing time and the effective moisture diffusivity. Yet when ultrasound is applied, the increase of ultrasonic energy density could shorten dehydration time of the following AD process and total processing time. UOD prior to AD has positive effects on improving carotenoid content of product and reducing process energy cost. So it's definitely concluded that UOD pretreatment is an effective and complementary method for traditional AD process.