Optimised Recovery of Phenolic Compounds from Graciano Grape Pomace by Ultrasound-Assisted Extraction: Implications for Enology and Viticulture

Abstract

Solid-liquid extraction with mechanical agitation is a common technique for recovering bioactive compounds from grape pomace (GP). This study aimed to optimise the extraction of phenolic compounds from Graciano GP by evaluating the effects of drying method (oven and freeze-drying), solvent type (water, hydroalcoholic solution and methanol), and ultrasound extraction time (15 and 30 min). The extracts were characterised by measuring colour parameters via spectrophotometry, quantifying total phenols and total anthocyanins using enzymatic methods, and analysing phenolic composition by HPLC-DAD. The optimal conditions were freeze-drying at -85 °C, extraction with 100% methanol, and 30 min of ultrasound treatment, which maximised the recovery of phenolic compounds. The resulting extracts represent a rich source of bioactive compounds with potential interest for the food industry. Their composition also suggests promising potential perspectives for future applications in winemaking (particularly as potential natural alternatives to SO2) and in viticulture (as potential bioestimulant), which remain to be experimentally validated in real wine and plant models.