# Recovery of Polyphenols from Agri-Food By-Products: The Olive Oil and Winery Industries Cases
## 5 From Agri-Food Wastes to Polyphenols: Processing Techniques
### Extraction Processes
NF is adequate to selectively recover and concentrate low-molecular-weight polyphenols. Finally, RO is used for purification purposes [6]. Membrane separation processes have shown to be a suitable stage of pre-treatment for polyphenol recovery in olive mill [20; 44; 49; 51; 106; 114; 115; 116; 117; 118; 119; 120; 121] and winery [36; 61; 108; 110; 122; 123; 124; 125] residues. However, more studies are needed for the optimization and implementation of these technologies at an industrial level, for solid and liquid wastes. Examples of the application of different membrane techniques for the recovery of polyphenols from the olive mill and winery wastes are presented in Table 4. \begin{table}
\begin{tabular}{c c c c} \hline
**Technique** & **Sample** & **Membrane** & **Polyphenols Concentration** & **Reference** \\ \hline \multicolumn{4}{c}{Olive Mill Residues} \\ \hline \multirow{4}{*}{MF, UF and NF} & Olive mill & Permapore EOV 1046 (MF), & 2456 to 5284 \(\mu\)g mL\({}^{-1}\) (MF) & \multirow{4}{*}{[44]} \\  & wastewater & (UF) and PERMAPORE AEN & 1404 to 3065 \(\mu\)g mL\({}^{-1}\) (UF) & \\  & & 1812 BS (NF) & 373 to 1583 \(\mu\)g mL\({}^{-1}\) (NF) & \\ \cline{3-4}  & Olive mill & Microlab 130 S (MF) and & \multirow{3}{*}{7.2 g L\({}^{-1}\) of hydroxytyrosol} & \\  & wastewater & 18 PCI (UF) & & \\ \cline{3-4}  & & Becpod P550 (MF) and PES & 250, 250 and 430 mg in the NF & \\ \cline{3-4}  & MF, UF and NF & Wastewater & spiral membrane from 100 kDa & \\ \cline{3-4}  & & and 3–5 Da MWCO & & \\ \cline{3-4}  & NF and RO & Olive pomace & NF270 (NF), NF90 (NF) and & \\ \cline{3-4}  & & BW30 (RO) & & \\ \cline{3-4}  & Green leaves, dried & \multirow{3}{*}{Tubular ceramic membranes in } & \multirow{3}{*}{244.15, 57.63 and 289.93 mg g\({}^{-1}\)} & \\ \cline{3-4}  & leaves, and pitted & & & \\ \cline{3-4}  & olive pulp & & PES (UF, NF and RO) & \\ \cline{3-4}  & Olive mill & \multirow{3}{*}{Tubular ceramic zirconia } & \multirow{3}{*}{378, 98, and 190 g GAE L\({}^{-1}\) for olive mill wastewater, olive leaf extract and grape marc extract, respectively} & \\ \cline{3-4}  & & & & \\ \cline{3-4}  & & & & \\ \cline{3-4}  & & & & \\ \end{tabular}
\end{table} 
Table 4: Membrane techniques for polyphenols recovery from the olive mill and winery wastes. Figure 8: Membrane separation scheme. For instance, [PERSON] et al. [113] proposed a design of a purification plant for the recovery of polyphenols from olive mill wastewater, grape marc, and olive leaves. The proposed process was based on an integration of UF (tubular ceramic zirconia membrane), NF (spiral wound polymeric membrane), and RO (spiral wound polymeric membrane) techniques, and a final adsorption step. As a result, they obtained 378, 98, and 190 g GAE L\({}^{-1}\) for olive mill wastewater, olive leaf extract, and grape marc extract, respectively. Additionally, [PERSON] et al. [122], evaluated MF for the recovery of polyphenols from second reaching wine lees, with or without previous water addition to the effluent. MF was in total recirculation mode (V0.2 and MFP5, flat-sheet membranes) and in concentration mode (Plasma membrane-associated membranes (PAM) hollow fiber). After MF experiments, a sequential design of UF (ETNA01 PP and ETNA10 PP membranes) and NF (NF270 membrane) was employed in order to fractionate polyphenols and polysaccharides from wine lees [123]. MF led to obtaining a limpid permeate rich in polyphenols. UF has proven to be effective to separate the polysaccharides of the polyphenols, and NF membrane presented polyphenols rejections higher than 92%, achieving concentrated solutions with high antioxidant activity.