ABSTRACT
The aim of this study was to obtain the equilibrium moisture content of grape (variety ‘Tannat’) pomace through desorption isotherms, to evaluate the drying kinetics, determine the coefficient of effective diffusivity and physico-chemically characterize the grape pomace and the product obtained after drying. The desorption isotherms were determined at 50, 60 and 70 ºC and the experimental data were fitted using the GAB model (Gugghenheim, Anderson and de Boer). Drying was evaluated using a 22 factorial experimental design with three center points and effective diffusivity was obtained through the diffusion model of Fick’s second law. The grape pomace was characterized regarding the contents of moisture, protein, carbohydrates, lipids, ash and dietary crude fiber. The obtained isotherms showed sigmoid shape and the experimental data fitted well to the GAB model. The drying curves showed only a decreasing rate period. The effective diffusivity values were within the range for organic materials. Dry grape pomace showed high contents of protein and fiber and can be used in the development of new products, in order to increase the nutritional content and add value to this byproduct.
Key words:
byproducts; isotherms; proteins; fibers
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(1) Blower sends air to the device; (2) psychrometer reads inlet air conditions; (3) electric panel that informs drying temperature, dry bulb temperature and wet bulb temperature and controls the drying air speed; (4) anemometer that checks air speed; (5) scale attached to the dryer constantly monitoring sample mass; (6) sample placed on a metal tray with perforated bottom inside the tunnel
