The effect of ultrasound assisted osmotic dehydration as a pre-treatment on the physical and chemical properties of cantaloupe

Abstract

This study was conducted to examine the change in chemical and physical properties of the cantaloupe (Cucumis melo L.) dried at 70°C after pre-treated in osmotic solution (sucrose with 0, 20, 40 and 60°Brix) with and without the aid of ultrasound in order to provide a clear image for the alteration of product quality after being processed. The initial moisture loss and solid gain during the pre-treatment were investigated. Moreover, the experimental data obtained during the drying processes were fitted with six theoretical models to predict the drying kinetics of cantaloupe. The results showed that as the osmotic solution concentration increased and the combination of ultrasound was applied, the more the water loss (from -3.23 to 15%) and solid gain (from -3.39 to 13.06%). In addition, among all the proposed drying models, the Midilli model was found to best appropriate for the drying characteristics of cantaloupe. The ultrasound assisted osmotic dehydration led to the reduction in drying time by approximately 19% in comparison with the value for the untreated ones. The considerable differences in the chemical and physical properties of cantaloupe after pre-treatment with osmotic solution with and without ultrasound were observed. At the same sucrose concentration, sample pre-treated with ultrasound-assisted osmotic rehydration exhibited the same shrinkage degree, same rehydration capacity, higher porosity (up to 20%), lower total phenolic content (2.5 times) and lower 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging activities (up to 13%) than the untreated samples. However, the combination of ultrasound could save the sugar amount used in osmotic solution as well as preserve total phenolic compounds and antioxidant activity to deliver the similar effect in reducing the drying time as compared with the single osmotic dehydration. Keywords: cantaloupe, osmotic, ultrasound, drying kinetics, shrinkage, porosity, rehydration capacity, phenolic content, DPPH.