Innovative processes for the extraction of bioactive compounds from winery wastes and by-products

Grape processing by-products (pomace, stalks, vine shoots, and lees) represent a cheap and rich source of bioactive compounds, including polyphenols, anthocyanins, tannins, and vitamins, with high commercial relevance for their potential applications in food, feed, cosmetic, and pharmaceutical sectors. Recovery of these compounds is a key point to improve the sustainability of wine production and create economic and social benefits. Conventional solid-liquid extraction (SLE) methods offer a simple approach to recover these compounds from winery by-products, but they are typically time and energy-consuming and may require the use of large amounts of organic solvents, which are often toxic and harmful, relatively high temperature, thus causing loss of thermolabile compounds, and lead to low extraction yields and selectivity (purity). Hence, the utilization of low energy-demanding, more sustainable, and “green” alternative extraction processes has been recently proposed. This chapter aims to provide an overview of the most advanced technologies (pulsed electric fields, high voltage electrical discharges, ultrasounds, microwaves, super- and subcritical fluids) applied to either assist or as an alternative to SLE for the valorization of grape processing by-products. In particular, the basic principles and the impact of processing parameters of the above-mentioned innovative technologies, alone or in a comparative way, on extraction yields, selectivity, and environmental sustainability is critically discussed.