Application of pressurized liquid extraction to grape by-products as a circular economy model to provide phenolic compounds enriched ingredient

The aim of this study was to valorise wine-making by-products optimizing the recovery of phenolic compounds from Cannonau grape pomaces using Pressurized Liquid Extraction (PLE). To achieve these goals, PLE experiments were performed by a Response Surface Methodology (RSM) based on a Central Composite Design 23 model to address the polar compound extraction. The selected independent variables were: temperature, composition of extractant solvent (% ethanol) and extraction time. The response variables were extraction yield and recovery of phenolic compounds. Phytochemical profile of PLE extracts was analysed by high-performance liquid chromatography coupled to a time-of-flight mass analyser (HPLC-ESI-TOF-MS) in order to address the individual phenolic extraction effectiveness. Hence, the optimum values to maximize phenolics extraction were 130 °C, 55% ethanol and 22 min. Extraction results obtained by using PLE system was compared with that obtained with conventional solid-liquid extraction. The proposed experimental model has proven to be a valuable alternative method to optimize extraction of bioactive compounds from wine-making by-products.