Enhanced osmotic dehydration of watermelon rind using honey–sucrose solutions: A study on pre-treatment efficacy and mass transfer kinetics

Abstract

This study investigates the osmotic dehydration process of watermelon rind using a solution composed of honey and sucrose. The impact of the ratio of rind-to-solution and temperature on the process is illustrated. Pre-treatments such as blanching, microwaves, and ultrasonication were utilized. Ultrasonication reduces the time needed for osmosis in a sample, resulting in increased fluid loss and solute uptake; therefore, it was selected as the method to investigate the kinetics and modelling of mass transfer. The effective diffusivities for water loss (ranging from 3.02 × 10−5 to 4.21 × 10−4 m2 s−1) and solid gain (ranging from 1.94 × 10−6 to 3.21 × 10−6 m2 s−1) were shown to increase with process variables such as temperature and the rind-to-solution ratio. The activation energy decreased as the process temperature increased, ranging from 3.723 to 0.928 kJ mol−1 for water loss and from 1.733 to 0.903 kJ mol−1 for solid gain, respectively. The sample treated with microwaves exhibited the maximum dehydration coefficient, rendering it appropriate for producing dehydrated products. Five empirical models were utilized, with the power law model (R 2 = 0.983) and the Magee model (R 2 = 0.950) being the most suitable for water loss data and solid gain, respectively.

Keywords

• watermelon rind
• osmotic dehydration
• pre-treatments
• effective diffusivities
• activation energy
• overall dehydration coefficient