Abstract
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.
Highlights
Papaya (Carica papaya L) belongs to the family of Caricaceae, low-cost climacteric-type fruits widely grown in tropical and sub-tropical regions [1,2]
This pattern of water loss and solute gain may be due to the immersion time progressed; the water migrated from the sample to solution and solute from solution to sample which decreased the concentration gradient between the solution and the solid content of papaya
The rate of water loss and solute gain increased with the increase of osmotic solution concentration, time and temperature
Summary
Papaya (Carica papaya L) belongs to the family of Caricaceae, low-cost climacteric-type fruits widely grown in tropical and sub-tropical regions [1,2]. Papaya is a good source of β-carotene, lycopene, provitamin-A vitamin C, iron, calcium, protein, carbohydrates, phosphorous and associated antioxidant activity [1]. This fruit is perishable due to the presence of higher water content (80%–90%) [2]. In every year the post-harvest losses of papaya in Bangladesh are approximately 40% to 50% [3]. Due to the lack of post-harvest and processing technology, lots of fresh and ripe fruits are damaged every year. There is increased interest in processing of the fruits to prevent this situation.
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