Pretreatments for melon drying implementing ultrasound and vacuum

The aim of this work was to evaluate the use of ultrasound, osmotic dehydration and vacuum as a pretreatment on melon drying and product quality. The pretreatment consisted in four processing conditions, using vacuum and/or ultrasound and a control sample with no application of ultrasound and vacuum. Melon samples were immersed in a liquid medium (distilled water or sucrose solution) and pretreated for 10, 20 and 30 min. The drying process was conducted in a fixed bed dryer at 60 degrees C and air velocity of 2 m/s. The dried pretreated samples with ultrasound and with a combination of ultrasound and vacuum presented faster drying rates. Evaluation of the final product was performed by means of total carotenoid content, texture, color and sensorial test. Dried melon pretreated using ultrasound and vacuum combined obtained higher total carotenoids content, softer texture and total color difference similar to the untreated dried fruit. Sensory evaluation showed that this pretreated sample had good acceptance and no significant difference from the dried untreated melon. Therefore, the use of ultrasound or a combination of ultrasound and vacuum as a pretreatment could improve the efficiency of melon drying, being an alternative to traditional drying and suitable to an industrial context. (C) 2016 Elsevier Ltd. All rights reserved.