Polyphenols from Winery by-products: Conventional versus Unconventional Extraction Methodologies

A large number of studies have already demonstrated that winery by-products (WBPs) are a valuable source of natural antioxidants, especially due to their phenolic content. These residues can be reused as new ingredients in the food, cosmetic, and pharmaceutical industries. For that reason, a scientific foundation for the comprehension of extraction methods’ efficiency is essential for starting the reuse of these by-products on a large scale. Numerous phenolic compounds extraction techniques under different conditions are currently being investigated. There has been a growing scientific interest in these phytochemicals, driven by the adoption of more eco-friendly extraction techniques that facilitate higher extraction yields. To extract the phenolic compounds present in WBPs, conventional methods as well as nonconventional extraction methods can be employed. The first ones, which have been used for a very long period, include Soxhlet extraction, maceration, reflux extraction, and others. Nonconventional methods, widely recognized as eco-friendly methods, such as ultrasound-assisted extraction (UAE), microwave-assisted extraction (MAE), accelerated solvent extraction (ASE), and supercritical extraction (SE), among others, provide higher extraction yields and high-quality extracts. This chapter will explore the extraction methodologies of phenolic compounds from WBPs produced by the wine industry, with a focus on both conventional and unconventional techniques. Additionally, the grape varieties mentioned in this review are suitable for production in Portugal under Designation of Origin (DO) and Geographical Indication (GI) classifications.