Mass transport properties of watermelon tissue in osmotic solutions and effect of osmotic dehydration on frozen watermelon quality

Mass transfer during osmotic dehydration of watermelon has been studied. The analytical solution of Fick's law for unsteady state mass transfer in cylindrical configuration has been used to calculate the effective diffusion coefficients over a range of temperature (5, 35, 55 degrees C) and concentration (40-60% wt/wt) of osmotic solution. The effective diffusion coefficient was modelled as a function of concentration and temperature of osmotic solution by an Arrhenius type equation. A high degree of correlation was observed between predicted and experimental values of the effective diffusion coefficient. Effective diffusion coefficient values increased when (a) solute concentration increased and (b) temperature of osmotic solution increased. The mass transfer was higher for osmotic solutes when the molecular weight of the carbohydrate was lower. The effect of the selected osmotic solute was also evaluated on the quality of frozen watermelon tissue. Pre-treated watermelon samples exhibited significantly improved quality and sensory characteristics, such as intense red color, good flavor, consistent texture, increased lycopene content, and stabilization during subsequent frozen storage.