Osmo-convective drying behavior of blueberries

The kinetics of moisture loss and solids gain during osmotic dehydration of blueberries under different conditions of temperature (37--60°C), concentration of the sucrose solution (47--70°Brix) and contact time between fruit and sucrose solution (0.5--5.5 h) were studied, and modeled based on Fick's law of unsteady state diffusion. The rates of moisture loss and solids gain were also related to temperature and sucrose concentration.The second stage convective drying behavior of osmo-dehydrated blueberries was evaluated in a forced air cabinet dryer (temperature: 50°C, relative humidity: 14%, air velocity: 0.6 m/s) with a cross-flow tray arrangement. Osmotic dehydration pre-treatments included different combinations of temperature, sucrose concentration and contact time. Fick's second law of unsteady state diffusion was used to model the air drying kinetics.The quality of two-stage osmo-convective dried blueberries with respect to color, texture and rehydration ratio was evaluated. The parameters analyzed for color were the total color difference (DeltaE) and, the (a/b) ratio as the indicator for the red-blue color. The texture analysis included evaluation of the hardness, chewiness and stickiness of the osmo-convective dried blueberries. (Abstract shortened by UMI.