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 °Brix) and osmotic solution temperatures (35, 45 and 55 °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 × 10⁻⁹ to 4.31 × 10⁻⁹ m²/s and 3.01 × 10⁻⁹ to 5.61 × 10⁻⁹ m²/s, respectively. Osmotically pretreated samples were dried with a convective method at a temperature of 70 °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 °C with the lowest concentration of 40 °Brix resulted in a significant decrease in phenolic content, antioxidant activity, and vitamin C content while higher osmotic solution concentration of 60 °Brix and the lowest temperature of the process (35 °C) retained maximum bioactive compounds.

The objective of the present study was to evaluate the effect of boiling duration on physicochemical, bioactive compounds, antioxidant activity, color, and texture properties of pumpkin ( Cucurbita maxima). The pumpkin was subjected to boiling for 1, 5, 10, and 20 min at 100 ℃. The physicochemical analyses showed that pH, moisture, and water solubility index were increased, whereas ash content was decreased with increasing the boiling time. Prolong boiling exhibited a detrimental effect on bioactive compounds of pumpkin, and it was found that 20 min of boiling caused about 25.91% ± 2.21% loss of total phenolic content, 14.79% ± 1.03% loss of total carotenoids content, and 18.46% ± 1.34% loss of antioxidant activity. A kinetic study was conducted to quantify the losses occurring in bioactive compounds, antioxidant activity, changes in color, and firmness of pumpkin. The study revealed that the logistic model can predict the variation in bioactive compounds and antioxidant activity with higher R². However, first-order kinetic models were found suitable to predict the changes occurring in bioactive compounds, antioxidant activity, color properties (L*, a*, b*, Chroma), and firmness. The total color changes (ΔE) showed a good fit with zero-order kinetic models (R²= 0.98). The t_1/2 and D-value were calculated for all measured parameters of pumpkin. These findings would be useful in designing thermal processes and related calculations of pumpkin.