Using Chemical Composition and Antioxidant Activity in Evaluation of Enological By-Products According to Type, Vinification Style, Season, and Grape Variety.

Large quantities of oenological by-products, rich in potentially extracted antioxidant compounds, are generated annually in the winemaking industry. With the purpose of their revalorization, different types of by-products (grape pomace, lees, and grape seed meal) from the winemaking industry from three vinification typologies (red, rosè, and white) and four varieties (Tempranillo, Syrah, Airén, and Zalema) in two grape growing seasons (2022 and 2023) were considered. Attention was focused on the content of protein, individual phenolic compounds (anthocyanins, flavonols, hydroxycinnamic acid derivatives, hydroxybenzoic acids, monomeric flavan-3-ols, and procyanidins), and antioxidant activity (DPPH, ABTS, and cyclic voltammetry). The data obtained showed considerable amounts of protein (around 30%) in red lees and a high concentration of phenolic compounds in the by-products, especially anthocyanins and flavonols in the by-products derived from rosè vinifications and flavan-3-ols, procyanidins, and hydroxybenzoic acids in red grape by-products. The antioxidant activity was different between the by-products. Specifically, the electrochemical behavior evaluated by cyclic voltammetry showed some significant differences. Finally, a linear discriminant analysis based on chemical and antioxidant data allowed for differentiating the samples depending on the type of by-product, type of vinification, and variety.