# Recovery of Polyphenols from Agri-Food By-Products: The Olive Oil and Winery Industries Cases
## 3 Polyphenols from Wine Production Wastes: Source and Applications  
Wine production is one important agricultural activity, _Vitis vinifera_ being the most cultivated species for wine production. Wine production regions are mainly located in Europe (Italy, Spain, France, Germany, and Portugal) and America (USA, Argentina, and Chile), but also in Australia and South Africa [7]. During vinification, only 30-40% of the phenolic compounds are extracted [8], and the process generates different types of waste and by-products such as grape pomace, grape stems, wine lees, and wastewater. One ton of grapes generates approximately 0.13 t of pomace, 0.03 t of stems, 0.06 t of lees, and 1.65 m\({}^{3}\) of wastewater [7; 27]. Although the residues of wine production are mainly produced in the harvest period, they are distributed throughout the year causing environmental problems if they are not properly disposed of. These residues, which have commonly been considered a problem, are rich in bioactive compounds with potential uses as food additives, nutraceuticalals, and/or cosmeceuticals [7]. The main phenolic compounds identified in wine production waste are shown in Table 2.  
At present, the valorization of winery by-products is mainly represented by their use as soil fertilizers, production of biomass, and animal feeding. Nevertheless, some compounds present in winery by-products are phytotoxic and show antimicrobial effects during composting, which affect their use for this purpose. Regarding its use in animal feed, certain components, such as condensed tannins, negatively affect the digestibility of animals [31; 32]. Therefore, its valorization as a source of bioactive compounds for application in the pharmaceutical, cosmetic, and food industries is a smart alternative [31]. The main types of wastes generated in the winery industry are grape pomace, grape steams, \begin{table}
\begin{tabular}{c c c} \hline \hline
**Sample** & **Identified Phenolic Compounds** & **Concentration** & **Reference** \\ \hline \multirow{8}{*}{Grape pomaces} & \(p\)-hydroxybenzoic acid & 6.03–50.9 mg kg\({}^{-1}\) dw & \\  & Protocatechuric acid & 4.34–57.4 mg kg\({}^{-1}\) dw & \\  & Gallic acid & 149–987 mg kg\({}^{-1}\) dw & \\  & Ellagic acid & 196–1040 mg kg\({}^{-1}\) dw & \\  & Vanillic acid & 97.5–302 mg kg\({}^{-1}\) dw & \\  & Syringic acid & 24.1–660 mg kg\({}^{-1}\) dw & \\  & \(p\)-coumaric acid & 2.85–77.4 mg kg\({}^{-1}\) dw & \\  & Chlorogenic acid & 4.51–102 mg kg\({}^{-1}\) dw & \\  & Caffe acid & 75.1–82.8 mg kg\({}^{-1}\) dw & \\  & Resveratrol & 6.10–78.0 mg kg\({}^{-1}\) dw & \\  & Quercetin & 547–848 mg kg\({}^{-1}\) dw & \\  & Rutin & 8.11–569 mg kg\({}^{-1}\) dw & \\  & Kaemferol & 454–553 mg kg\({}^{-1}\) dw & \\  & Catechin & 403–3711 mg kg\({}^{-1}\) dw & \\ \hline \multirow{8}{*}{Grape stems} & Gallic acid & 70.4–469 mg kg\({}^{-1}\) dw & \\  & (+)-Catechin & 385–1858 mg kg\({}^{-1}\) dw & \\  & (+)-Epicatechin & 12.3–189 mg kg\({}^{-1}\) dw & \\  & Procyanidin B3 & 138–993 mg kg\({}^{-1}\) dw & \\  & Procyanidin B2 & 36.0–165 mg kg\({}^{-1}\) dw & \\  & Epicatechin gallate & 34.2–130 mg kg\({}^{-1}\) dw & \\  & trans-Cafaric acid & 5.1–274 mg kg\({}^{-1}\) dw & \\  & trans-Resveratrol & 74.0–266 mg kg\({}^{-1}\) dw & \\  & 3-Viniferin & 167–499 mg kg\({}^{-1}\) dw & \\ \hline \multirow{8}{*}{Wine lees} & (+)-Catechin & 43.1–50.1 mg L\({}^{-1}\) & \\  & (-)-Epicatechin & 7.7–517.1 mg L\({}^{-1}\) & \\  & Procyanidin B1 & 15.3–46.8 mg L\({}^{-1}\) & \\  & Procyanidin B2 & 19.4–29.7 mg L\({}^{-1}\) & \\  & Myricetin & 1.3–1.8 mg L\({}^{-1}\) & \\  & Quercetin & 4.2 mg L\({}^{-1}\) & \\  & Gallic acid & 8.1–35.9 mg L\({}^{-1}\) & \\  & trans-cafaric acid & 21.2–23.3 mg L\({}^{-1}\) & \\  & trans-coutaric acid & 1.3–9.6 mg L\({}^{-1}\) & \\  & Caffe acid & 0.7 mg L\({}^{-1}\) & \\  & \(p\)-coumaric acid & 0.6–0.9 mg L\({}^{-1}\) & \\  & Ferulic acid & 0.2–0.9 mg L\({}^{-1}\) & \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Phenolic compounds in winery wastes. wine lees, and wine processing wastewater.