Effect of Ultrasound-Assisted Osmotic Dehydration Pre-Treatment on Tray Drying of Musk Melon Cubes

This study investigated the effect of ultrasound-assisted osmotic dehydration as a pre-treatment before tray-drying of Muskmelon (Cucumis melo). The effects were measured in terms of water loss and solute gain during osmosis, convective drying time, shrinkage, colour change, rehydration ratio, texture, and microstructure. At first, muskmelon cubes of side 2 cm and weight 10 ± 0.05 g were immersed in a sucrose solution of 30°Brix, maintaining a fruit-to-solution ratio of 1:10. Then, the sucrose solution containing samples were subjected to ultrasonication for 30 min. The osmotic dehydration was further carried out for 150 min with agitation at 150 rpm. In order to optimize the ultrasound power for the studied parameters, the power of magnitude 162.5, 325, 487.5, and 650 W were applied. All different powers of ultrasound significantly influenced the studied parameters to some extent. The influence was less at low power and continuously increased with an increase in the magnitude of power. Ultrasound-assisted osmotic dehydration resulted in higher water loss and lower solute gain during osmosis. It significantly reduced the tray drying time, decreased the colour change, reduced shrinkage, and improved the rehydration ability of dried muskmelon. Ultrasound-assisted osmotic dehydration at 325 W ultrasound power resulted in the texture of rehydrated muskmelon closer to fresh muskmelon. However, the higher power of ultrasound (487.5 & 650 W) resulted in a softer texture. The microstructure analysis of dried muskmelon revealed the formation of microscopic channels. The increase in ultrasound power resulted in an increased number of microchannels. Hence, ultrasound-assisted osmotic dehydration pre-treatment followed by tray drying can ensure the availability of efficiently dried good quality muskmelon, which can be consumed after rehydration as an alternative of fresh muskmelon, even during the off-season.

Graphical Abstract