Phenolic compounds recovery from grape skin using conventional and non-conventional extraction methods

The aim of this work was to recover phenolic compounds from grape skin from sparkling production in the Brazilian semi-arid region, using conventional and non-conventional extraction methods Firstly, the effect of solid:liquid ratio (1:3-1:17) and ethanol concentration (8-92%) on the phenolic content and antioxidant capacity of grape skin extracts obtained by mechanical agitation were evaluated. Solid:liquid ratio of 1:10 and 50% ethanol were chosen as the most adequate conditions for phenolic compounds recovery. Then, in the selected conditions, extraction kinetics using ultrasound-assisted and microwave-assisted extractions were determined for comparison. Ultrasound-assisted extraction showed the best performance, resulting in an extract with a phenolic content twice higher than the obtained by mechanical agitation, in a very shorter time (9 min). Regarding phenolic profile, malvidin-3-O-glucoside was the main compound found in the extracts, followed by quercetin, rutin, catechin and epicatechin.