Influence of different extraction methods on the compound profiles and functional properties of extracts from solid by-products of the wine industry

This study evaluated the impact of three different extraction methods, agitation, ultrasound, and supercritical fluid extraction (SFE), on the functional properties and bioactive compound profiles of stalks, a by-product of the wine industry. For agitation and ultrasound methods different concentrations of ethanol as solvent were evaluated while for optimization of SFE conditions Response Surface Methodology (RSM) was applied. Supercritical fluid conditions with 270 and 300 bar, 50 and 40 °C and 3 and 2 extraction hours were optimal to obtain high extraction yields and extracts with high antioxidant activity, respectively. The extracts obtained by SPE at high pressures and temperatures (300 bar and 50 °C) showed antihypertensive activity and higher activity against bacteria while those obtained at low pressures and medium temperatures (200 bar and 45 °C) presented higher activity against yeasts. Extracts obtained with the agitation and ultrasound methods were rich in phenolic compounds and showed higher antioxidant activity, while those extracted with supercritical fluids contained higher amounts of lipophilic substances such as terpenoids, fatty acids and oxylipins associated to antihypertensive and antimicrobial activities. The effective recovery of their entire host of bioactive components will increase the overall value of the industry by decreasing the production of agricultural residues.