Pressurized liquid extraction as an innovative high-yield greener technique for phenolic compounds recovery from grape pomace

Grape pomace (GP) is the solid organic material remaining after grape industrialization in the production of wines and juices. It comprises skin, seeds, and residues of pulp or must. This by-product, still considered underused, is rich in bioactive compounds, especially phenolics, being attractive for pharmaceutical and food markets. Phenolic compounds have bioactive properties such as antioxidant, anti-inflammatory, antitumoral, antihyperglycemic, antiaging, and vasodilating. Among many emerging techniques applied to recover these phytochemicals from grape pomace, pressurized liquid extraction (PLE) has stood out for advantages such as green solvents, higher extraction yields, selectivity, and a high level of automation. This review addresses the most recent updates of PLE and its application to obtain phenolic extracts from GP. Different PLE methods have been optimized for that purpose with an implementation of the technique regarding apparatus and automation and the application of greener solvents, such as hot water and natural deep eutectic solvent (NADES). Accelerated solvent extraction (ASE) is an emerging PLE technique that has been highlighted by demanding less time and manual operation. Moreover, since it is performed quickly, it allows the application of high temperatures to thermosensitive molecules, such as phenolics. Using ASE and green solvents, it increases the yield of phenolic and enhances extract bioavailability from GP. Choline chloride/urea and choline chloride/oxalic acid diluted in water showed to be suitable NADESs for PLE applications. However, the high viscosity of NADESs is still a barrier to this technique.