Study of the drying kinetics by hot air of grape marc

Abstract

The drying kinetic of grape marc (Vitis vinifera L.) to different temperatures and its influence on the antioxidant activity of the extracts obtained was determined. The experiments were carried out in a lab dryer to three air temperatures (40, 50 y 60ºC) and a constant air velocity. The extraction of poliphenols was developed to 55 ºC, 100 rpm, ratio solute-solvent 1:10 (m/v) during 4h, employing an ethanol-water mixture in a proportion of 1:1 (v/v) as solvent. The drying kinetic may be satisfactorily described by means of a theoretical model, derived from the Fick´s law, and the empirical model of Peleg. Effective difusivities corresponding to each drying period were determine from the theoretical model. The antioxidant activity of the extracts decreased significatively to 60ºC respect to the remaining temperatures of drying researched.