Abstract
The aim of this study was to evaluate the oil and bioactive contents of grape waste by both conventional and microwave-assisted extraction (MAE) methods. Other controlled factors included the segment solvent used (n- hexane-methanol, n-hexane-ethanol), the solid/solvent ratios (1 : 5, 1 : 10, 1 : 20 g/mL) and in MAE, the microwave powers (40 W, 240 W and 440 W). The extracts were analysed for the contents of fatty oil, lipid hydroperoxide content (LP), total phenolic content (TPC), total flavonoid content (TFC), and antioxidant capacity. The optimal conditions for the grape oil recovery were at 240 W, using n-hexane-ethanol solvent, and the ratio of 1 : 10 by using the MAE method. At the same ratio conditions, the highest contents of LP and TPC were 0.032 mM (at 440 W) and 43.657 mg gallic acid (AG)/dry weight (at 240 W). At 440 W and ratio of 1: 10, TFC peaked the highest point at 37.862 mg quercetin/g dry weight. The results indicated that grape waste is a valuable input for a wide range of applications in nutraceutical and food industries, offering an additional economic by-product for the grape processing.
