## 5 Methods of Extraction of Bioactive Substances from Grape and Winery By-Products
### Supercritical Fluid Extraction (SFE)  
[PERSON] et al. (2008) analyzed the effect of extraction methods on antioxidant potential in GPE, comparing conventional SLE, Soxhlet, and SFE with CO\({}_{2}\) and CO\({}_{2}\) with ethanol as a co-solvent. The results showed that the addition of a co-solvent such as 15% ethanol enhances yield and antioxidant activity due to proportional changes in the characteristics of the solvent mixture. However, the antioxidant activity and total phenolic yield (TPC) of the extracts obtained were significantly lower than those achieved using other extraction methods. SFE was best for non-polar compounds such as fatty acids and was able to extract important compounds not detected in conventional extracts [62]. SFE is a new technique for extracting target analyzers from solid matrices using supercritical fluids. A supercritical fluid is a substance above critical temperature and pressure, located at a borderline between liquid and gas, exhibiting high solubilizing power, high effusivity, low viscosity, and low marginal surface tension, allowing rapid mass transfer and efficient extraction. SFE is an environmentally sustainable alternative to conventional solvent extraction as it avoids toxic solvents and is fast, automated, and selective [63]. The goal of SFE is to use non-toxic organic solvents, minimize pollution, achieve quick extraction periods, and be extremely selective. SFE is faster, automated, more selective, and less harmful to the environment than traditional solvent extraction. Coordinated solvent density must be attained and excessive use of hazardous solvents must be avoided. Furthermore, the breakdown of active chemicals is restricted throughout the extraction process due to the lack of light and air [64].  
Also, [PERSON] et al. (2013) aimed to evaluate the use of different extraction methods, including supercritical fluid extraction (SFE), using CO\({}_{2}\) and CO\({}_{2}\) with co-solvents, to obtain extracts from Merlot and Syrah grape pomace. The study compared the global extraction yield and antibacterial activity of the extracts. Although SFE yielded lower amounts of extract, it effectively inhibited the growth of various microorganisms, particularly Gram-positive bacteria, demonstrating its potential as an efficient method for obtaining antimicrobial compounds from grape pomace [65]. [PERSON] et al. (2014) focused on optimizing a supercritical fluid extraction method that employs a liquid trap instead of a solid trap for polyphenol extraction from grape marc. The research aimed to maximize extraction efficiency while avoiding organic solvents. The study optimized key variables, including CO\({}_{2}\) modifier content and extraction time, achieving successful extraction of polyphenols with significant biological activity, highlighting the potential for profitable use of grape marc as a source of bioactive compounds [66]. [PERSON] et al. (2020) investigated the supercritical extraction of anthocyanins from grape pomace, utilizing ethyl alcohol as a co-solvent. The study aimed to maximize anthocyanin yield while evaluating the effects of extraction time on yield and total antioxidant capacity (TAC). The results indicated effective extraction of anthocyanins, with the total monomeric anthocyanin content (TMAC) recorded at 1932.1 mg/kg dry matter. While the yield was lower than traditional methods, the research emphasized the need for further optimization to enhance economic viability and extraction efficiency for anthocyanin materials [67].