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Dragon fruit belongs to the family Cactaceae and it includes 2,500 species. Vietnam is the world’s leading producer of dragon fruit. India ranks 9th in production of 26,000 MT. Andhra Pradesh ranks 5th in production of dragon fruit and is around 455 MT. Dragon fruit is emerging as a super crop because of its several health and therapeutic benefits and ease of cultivation even in degraded land. It is rich in potassium, iron, sodium, calcium, fiber and other minerals. It has got significant source of antioxidants. It is believed to be able to lower cholesterol concentration to balance blood sugar, and be able to prevent colon cancer to strengthen kidney functioning and bone strength. It has the ability to promote the growth of probiotics in the intestinal tract. The effect of osmotic solution concentrations (40, 50, 60, 70°Brix), solution temperatures (40, 50, 60, 70°C) and immersion times (30, 60, 90, 120,150, 180, 210, 240 min) on osmotic dehydration of dragon fruit (Hylocereus polyrhizus) slices (square shape, 2×2 cm) were studied at fruit to solution ratio of 1:4. Central composite rotatable deign (CCRD) was used in Response surface methodology (RSM) to optimize the osmotic solution concentration, solution temperature and immersion time during osmotic dehydration by maximizing water loss (WL) and minimizing solid gain (SG). The optimized process parameters were osmotic solution concentration of 65.3°Brix, solution temperature of 56.5°C and immersion time of 240 min with a maximum water loss of 57.93%, minimum solid gain of 8.01% and maximum weight reduction of 50.43%. The optimized dragon fruit slices were dried in a tray dryer at 40 to 70°C. The time required to dry dragon fruit slices till it attains equilibrium moisture content (8% d.b.) were 540, 420, 240 and 180 min. respectively. Drying curves obtained from the experimental data were fitted to different drying models and found that two term, two term exponential and Kaleemullah models were suitable to predict the moisture ratio of osmo-tray dried dragon fruit slices. The effective moisture diffusivity, Deff of osmotically air dried dragon fruit slices ranged from 4.56×10-11 to 1.04×10-10 m2s-1 as drying air temperature increased from 40 to 70°C. The activation energy and the diffusivity constants of the osmo air dried dragon fruit slices were 28 kJ mol-1 K -1 and 2.13×10-6 m2 s-1 during 40 to 70°C tray drying. All biochemical parameters decreased for osmo dehydrated slices except carbohydrates is increased because of the addition of sugar in osmosis process. The colour values - L* and a* of dragon fruit slices increased from 10.79 to 16.41 and 6.68 to 16.48, whereas b* values decreased from 4.88 to 1.67 as drying temperature increased xiii from 40 to 70°C. Dragon fruit slices hardness, cohesiveness, gumminess, chewiness increased whereas springiness decreased and adhesiveness was not found as drying temperature increased from 40 to 70°C. The total mesophiles in intermediate moisture dragon fruit samples (15, 20, 25% d.b.) gradually increased from initial period to final storage period (60 days). Yeast and moulds were not present in intermediate moisture dragon fruit samples (15, 20, 25% d.b.) during 0 to 15 days and later they are formed in 30 to 60 days storage period. Acidophiles were not detected in intermediate moisture dragon fruit samples (15, 20, 25% d.b.) in 0 to 60 days storage period. Keywords: Dragon fruit, Drying models, Osmotic dehydration, Solid gain, Water loss, Weight reduction.