## 5 Methods of Extraction of Bioactive Substances from Grape and Winery By-Products
### Solid-Liquid Extraction (SLE)  
Solid-liquid extraction (SLE) is based on the selective solubility of one or more of the components of the solid in the liquid solvent. There are many ways to perform the SLE process. The \"shake filter\" approach based on stirring is one of the most popular. In addition, there are many other methods for extracting solids from liquids, including heating (Soxhlet). Soxhlet extraction involves repeatedly washing the matrix with a new solvent, which increases the analyte's potential solubility because a heated solvent is used. These are the primary benefits of this method over traditional maceration, which allows for cost savings in terms of time, energy, and subsequent financial inputs. On a medium or large scale, Soxhlet extraction can be transformed from a batch process to a continuous process on a huge scale [49]. To extract a component from a solid, there are two fundamental processes. These include mixing the solid with the solvent and separating the liquid from the solid phase. However, there are also some intermediate stages concerning the solubilization of the compounds, the movement of the solution from the inside of the solid mass to the surface, \begin{table}
\begin{tabular}{l l l} \hline
**Chemical Compositions** & **Representative Bioactive Constituents** & **References** \\ (**Content in g/100 g)** & **(Content in g/100 g)** & **(Content in g/100 g)** \\ \hline \multirow{4}{*}{Phenolic Acids (0.5–0.9 g/100 g) and & Gallic acid (0.03–0.05 g/100 g), p-hydroxybenzoic acid & \\  & (0.01–0.02 g/100 g), syringic acid (0.1–0.2 g/100 g), & \\  & & caffe acid (0.0005–0.001 g/100 g), p-coumaric acid & [24; 42; 47] \\  & (0.02–0.04 g/100 g), ferulic acid (0.002–0.03 g/100 g), & \\  & resveratrol (0.03–0.05 g/100 g) & \\ \hline \multirow{4}{*}{Flavonoids (0.05–0.1 g/100 g) and & Catechin (0.03–0.04 g/100 g), epicatechin & \\  & (0.01–0.02 g/100 g), quercetin (0.01–0.02 g/100 g), & \\  & & anthocyanins (malvidin–3-O-glucose & [2; 29; 31; 47] \\  & 0.005–0.006 g/100 g) & \\ \hline Vitamin E (0.02–0.05 g/100 g) and & \(\alpha\)-tocopherol (0.02–0.05 g/100 g), & \\  & (0.02–0.05 g/100 g) & \\ \hline Unsaturated Fatty Acids (UFA) & Linoleic acid (30–35 g/100 g), oleic acid (10–12 g/100 g), & [41; 46; 47] \\ (30–35 g/100 g) & alpha-linolenic acid (12–13 g/100 g) & [41; 46; 47] \\ \hline \multirow{2}{*}{Bioactive Polar Lipids (0.5–1.5 g/100 g)} & Phospholipids (0.5–1.5 g/100 g), & [46; 47] \\  & glycolipids (0.3–1.0 g/100 g) & \\ \hline \end{tabular}
\end{table} 
Table 1: Chemical composition and bioactive constituents of grape by-products. and finally, the movement of the extracted compounds from the inner surface of the solid to the volume of the solution. Finally, changes in concentration gradients, diffusion coefficients, or the boundary layer might increase the extraction efficiency, depending on the sample's properties and the molecules being targeted. The extraction technique, solvent type, temperature, extraction duration, particle size, and matrix composition can all affect these characteristics [50]. [PERSON] et al. (2011) focused on optimizing traditional organic solvent extraction for Pinot Noir seeds, investigating various extraction times and solid-liquid ratios. The results indicated that the seeds contained high levels of total polyphenols (73.66 mg GAE/g dry weight) and flavonoids (30.90 mg CE/g dry weight), with an optimal extraction time of approximately 19 h. This study also found a significant correlation between the concentration of polyphenols and their antioxidant capacity, suggesting that careful manipulation of extraction parameters can enhance yield and efficacy [51]. [PERSON] et al. (2007) examined the influence of temperature, particle size, and solid-liquid ratios on the extraction kinetics of total polyphenols from grape seeds. The findings indicated that extraction yields were positively influenced by increased temperature and smaller particle sizes, with most polyphenols being extracted within 200 min.