Osmotic Dehydration of Jamun Fruit in Molasses: Pretreatment, Process Optimization, Mass Transfer Studies, and Bioactive Retention

This study aims to develop an intermediate moisture whole Jamun ( Syzygium cumini ) fruit by sequentially employing microwave pretreatment, osmotic dehydration, and air drying. Molasses, a by‐product from the sugarcane industry, was used as the osmotic medium. The significant factors affecting osmotic dehydration were screened using Plackett‐Burman design. The response surface modeling coupled with numerical optimization suggested the optimum osmotic dehydration conditions as 45°C, 70% molasses, and 6% NaCl concentration. The Peleg model was found to best describe the mass transfer properties among various other well‐fitted models. The effective diffusivity of water and solids was 5.14 × 10 −9 and 9.4 × 10 −10 m 2 /s, respectively, when calculated using Crank's analytical solution for Fick's second law of diffusion. The microwave pretreatments were conducted at 40%, 60%, and 80% power (100% = 700 W) for 30, 45, and 60 s. Based on water loss, solid gain, and nutrient retention, 30 s pretreatment at 60% power was found to be optimum. The integrated processing time for Jamun fruits to reach a water activity of 0.6 was 0.5 min of microwave pretreatment, 300 min of osmotic dehydration, and 60 min of air drying at 60°C in a convectional hot‐air oven. There was an 8.2%, 7.0%, and 6.4% increase in total polyphenols, total flavonoids, and antioxidant capacity of these Jamun fruits when compared to whole air‐dried fruits.