Ultrasound-assisted extraction of anthocyanins and total phenolic compounds in Vitis vinifera L. 'Tempranillo' winemaking lees

Winemaking lees (WL) are the less exploited by-products from the winemaking industry. This by-product is generated after the fermentation of grape must and its composition is variable, although it is mainly made up of lysed yeasts, tartaric acid, colloids, polyphenols and ashes. Of all the compounds that can be found in lees, polyphenols exhibit particularly powerful bioactive properties and their extraction for their reuse in different matrices could be a matter of particular interest. Ultrasound-assisted extraction (UAE) has been used to extract both total anthocyanins (TA) and total phenolic compounds (TPC) from lees from Vitis vinifera L. 'Tempranillo' vinification. The optimization of six extraction variables (% methanol, pH, temperature, amplitude, cycle and ratio solvent:mass) was performed using a Box-Behnken design (BBD) where TA and TPC were considered independent variables. The UAE method that has been developed in this research could be a new rapid and efficient method to extract TPC and, coupled to chromatographic methodologies, identify up to fourteen different anthocyanins from WL. The objective of this study is to determine WL polyphenolic content and its potential for further uses in other procedures aiming to create value from vinification waste.