Influence of Osmotic Dehydration on Mass Transfer Kinetics and Quality Retention of Ripe Papaya (Carica papaya L) during Drying

The study aimed to investigate the mass transfer kinetics and nutritional quality during osmotic dehydration (OD) and air-drying of papaya. The papaya was osmotically pretreated by different concentrations of sugar solutions (40, 50 and 60 degrees Brix) and osmotic solution temperatures (35, 45 and 55 degrees C). The ratio of fruit to the solution was kept at 1:4 (w/v) and pretreated process duration varied from 0 to 240 min. The present study demonstrated that water loss and the solute gain rate increased with the increasing of osmotic solution temperature, concentration and time. Mass transfer kinetics of osmotically pretreated papaya cubes were investigated based on the Peleg's and Penetration models. The Peleg model showed the best fitted for water loss and solute gain whereas the Penetration model best described the water loss during osmotic dehydration of papaya. Effective diffusivity of water and solute gain was estimated using the analytical solution of Fick's law of diffusion. Average effective diffusivity of water loss and solute gain was obtained in the range from 2.25 x 10(-9) to 4.31 x 10(-9) m(2)/s and 3.01 x 10(-9) to 5.61 x 10(-9) m(2)/s, respectively. Osmotically pretreated samples were dried with a convective method at a temperature of 70 degrees C. The moisture content, water activity and shrinkage of the dried papaya were decreased when the samples pretreated with a higher concentration of the osmotic solution and greater process temperature. The results also indicated that the highest osmotic solution temperature of 55 degrees C with the lowest concentration of 40 degrees Brix resulted in a significant decrease in phenolic content, antioxidant activity, and vitamin C content while higher osmotic solution concentration of 60 degrees Brix and the lowest temperature of the process (35 degrees C) retained maximum bioactive compounds.