Antioxidant compounds extraction from coffee husks: the influence of solvent type and ultrasound exposure time

Coffee husk can be removed from the grain mainly by two different ways: the wet method and the dry method. Aiming to add value to the by-products of the coffee agroindustry, we analyzed the antioxidant properties of hydroalcoholic extracts of coffee husks obtained from the two different methods. The production of the extract followed a rotational central composite design, varying the ethanol proportion and the ultrasound exposure time in between. The results of the experimental planning were: extract volume yield; total phenolic compound and antioxidant activity expressed by the DPPH and FRAP methods. Mathematical models were constructed using the significant parameters for each response, and its predictive capacity was evaluated through an analysis of variance of the regression. Better results were found in extracts from husk obtained by the dry method using solvent in a proportion of 40-50% (v v -1 ) ethanol to 40-60 min. of ultrasound exposure.