# 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
\begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Technique** & **Sample** & **Solvent** & \begin{tabular}{c} **Experimental** \\ **Conditions** \\ \end{tabular} & \begin{tabular}{c} **Polyphenols Concentration** \\ \end{tabular} & **Reference** \\ \hline UAE & Olive pomace & Ethanol:water & 1:30, _w/v_, 50 \({}^{\circ}\)C, 5 & 55.1 mg g\({}^{-1}\) hydroxytyrosol, 381.2 & \\  & & 90:10, _v/o_ & min & mg g\({}^{-1}\) maslinic acid and 29.8 mg & [97] \\ UAE & Olive pomace & Water & 1:50 _w/v_, 30 \({}^{\circ}\)C, 75 & 19.71 \(\pm\) 1.41 mg GAE g\({}^{-1}\) & [98] \\ PLE & Olive pomace & Ethanol:water & 120 \({}^{\circ}\)C, 20 min & 5.8\% extraction yield (8 gr) & [53] \\ PLE & Olive leaves & Ethanol:water123 & 80 \({}^{\circ}\)C, 5 min & 53.15 mg GAE g\({}^{-1}\) & [99] \\  & & 450:50 _v/v_ & 40 \({}^{\circ}\)C, 350 bar, 60 & 0.76 \(\pm\) 0.15 CAE & [92] \\ SFE & Olive pomace & Carbon dioxide & \multicolumn{2}{c}{Pulse duration: 10} & \\  & & & \(\mu\)s, pulse period: & & \\ PEF & Olive leaves & \begin{tabular}{c} Ethanol:water \\ (25\% EtOH) \\ \end{tabular} & \begin{tabular}{c} 1000 \(\mu\)s, electric \\ field 1 kV cm\({}^{-1}\), \\ time: 30 min \\ \end{tabular} & 20.75 mg GAE g\({}^{-1}\) & [86] \\ \hline  & & & \multicolumn{3}{c}{Winery residues} \\ \hline SLE & Grape pomace & Ethanol:water & 1:25 _w/v_, 60 \({}^{\circ}\)C, 2 h & 196.2 \(\pm\) 22.7 mg GAE g\({}^{-1}\) & [58] \\ SLE & Grape pomace & Ethyl acetate & 1:10 _w/v_, 25 \({}^{\circ}\)C, 6 h & 70.5 \(\pm\) 0.03 mg GAE g\({}^{-1}\) & [28] \\ SLE & Grape skins & Ethanol & 0.10:1 _w/v_, 25 \({}^{\circ}\)C, 19 h & 3.22 mg GAE g\({}^{-1}\) & [55] \\ SLE & Grape pomace & Acetone & 1:12.5 _w/v_, 60 \({}^{\circ}\)C, 45 min & 31.25 mg GAE g\({}^{-1}\) & [100] \\ SLE & Wine lees & Methanol/2\% & 1:5 _w/v_, 25 \({}^{\circ}\)C, 60 & \\  & & & & \\  & & & & \\ UAE & Grape skins & Ethanol:water & 1:10 _w/v_, 28 \({}^{\circ}\)C, 9 & \\  & & & 50:50 _v/v_ & min & 80 mg GAE g\({}^{-1}\) & [56] \\  & & & \multicolumn{3}{c}{UAE:} & \\  & & & & \\  & & Ethanol:water & & & \\ UAE combined & \begin{tabular}{c} (ethanol \\ \end{tabular} & \begin{tabular}{c} UAE: 14 _w/v_, 80 \\ \({}^{\circ}\)C, 4 min \\ \end{tabular} & & & & \\  & & & & & \\  & & & & \\  & & & & \\  & & & & \\  & & & & \\ UAE & Grape pomace & Ethanol:water & 1:70 _w/v_, 20 \({}^{\circ}\)C, 60 & 438984 \(\pm\) 4034 ppm GAE & [57] \\  & & & & & \\  & & & & & \\  & & & & \\  & & & & & \\ UAE & Grape seeds, & Ethanol:water & 1:4 _w/v_, 50 \({}^{\circ}\)C, 3 & 188, 89.15, 63.46 mg GAE g\({}^{-1}\) for & \\ UAE & pomace, and & \begin{tabular}{c} (44\% of \\ stems \\ ethanol) \\ \end{tabular} & & & & & \\  & & & & & \\  & & & & \\ UAE & Wine lees & Ethanol 43.9\% & 1:60 _w/v_, 60 \({}^{\circ}\)C, 25 & 58.76 mg GAE g\({}^{-1}\) & [102] \\  & & & & & \\ PLE & Grape pomace & \
\begin{tabular}{c} Ethanol:water \\ 50:50 _v/v_ \\ \end{tabular} & & & & & \\ EAE & Grape seeds & Water, pH 3.55, & Enzyme dosage 20 & \\  & & & & & \\  & & & & \\  & & & & \\  & & & & \\ OH & Grape pomace &
\begin{tabular}{c} Ethanol:water \\ (30\% ethanol) \\ \end{tabular} & 400 V cm\({}^{-1}\), 50 \({}^{\circ}\)C, 60 min & 620 mg GAE 100 g\({}^{-1}\) & [85] \\ \hline \hline \end{tabular}
\end{table} 
Table 3: _Cont._extraction conditions were: ethanol:water 90:10 _v/v_, 50 \({}^{\circ}\)C, 5 min, 1:30 _w/v_ solid-to-liquid ratio, 135.6 W/cm\({}^{2}\) ultrasound intensity, and 60 kHz ultrasound frequency. Additionally, [PERSON] et al. [41] compared conventional (SLE) and non-conventional extraction techniques (UAE and MAE) for the recovery of phenolic compounds from grape skins of sparkling production. As a result, UAE had a major recovery (almost 80 mg GAE g\({}^{-1}\)) at the optimized extraction conditions of ethanol:water 50:50 _v/v_, 1:10 _w/v_ solid-to-liquid ratio, and 9 min of extraction time. To select the extraction technique, several issues must be considered. In addition to extraction yield, capital and operating costs, environmental concerns, operating time, or industrial scaling-up must also be considered.