Drying kinetics of grape seeds
2008
Roberts, John S. | Kidd, David R. | Padilla-Zakour, Olga
Drying of grape seeds representing waste products from white wine processing (Riesling), red wine processing (Cab Franc), and juice processing (Concord) was studied at 40, 50, and 60°C and constant air velocity of 1.5m/s. Equilibrium moisture content had a significant effect on the normalized drying curve and was determined for each grape seed at each drying temperature. Effective moisture diffusivity ranged between 1.57 and 3.96x10⁻¹⁰ m²/s for Riesling seeds, 2.93-5.91x10⁻¹⁰ m²/s for Concord seeds, and 3.89-8.03x10⁻¹⁰ m²/s for Cab Franc seeds. The temperature dependence of the effective diffusivity followed an Arrhenius relationship, and the activation energies were 40.14kJ/mol for Riesling seeds, 30.45kJ/mol for Concord seeds, and 31.47kJ/mol for Cab Franc seeds. Three thin-layer models were used to predict the drying curves: Page model, Lewis model, and the Henderson-Pabis model. All three models were found to produce accurate predictions compared to the mass average moisture loss for each grape seed variety (percent error less than 10%), and the Lewis model was shown to be an excellent model for predicting all three grape seed varieties (percent error less than 5%).
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