Green Extraction of Nutritional and Antioxidant Valuable Compounds from Wine By-Products
During the wine production process, more than a thousand tons per year of wastes and by-products are produced in wine-growing countries. These materials have a large number of valuable compounds with a high nutritional value and biological properties that should be recovered for producing wine in a more sustainable way. Among these compounds, polyphenols are present in large quantity and variety, and they are valuable because their daily consumption is associated with antioxidant, antiallergenic, anti-inflammatory, antimicrobial, antithrombotic, and cardioprotective properties. Conventional solid–liquid extraction (SLE) has been the main way used to extract these compounds. However, in many cases, this involves the use of contaminant solvents and high temperatures, with the subsequent degradation of thermolabile compounds. Thus, the use of new green technologies that can partially or totally replace conventional methodologies is being investigated for reducing the use of solvents, as well as the temperature and the treatment time. In the different sections of this chapter, the application of conventional (SLE) and innovative (pulsed electric fields, pulsed ohmic heating, high voltage electrical discharges, ultrasound-assisted extraction, supercritical fluid extraction, pressurized hot water, microwave-assisted extraction, extraction with β-cyclodextrins, and high pressure/high temperature) extraction processes on the different wine industry wastes and by-products (e.g., pomace, skins, seeds, wine lees, leaves, and vine shoots) is discussed for obtaining valuable products, particularly polyphenols. It was concluded that the type of waste or by-product, the pretreatment applied, the extraction technique, and the solvent used will notably influence the composition and quality of the extracts. In addition, the possible applications of the extracted compounds are also mentioned.