Table 1.
The mechanism, advantages, disadvantages, and example(s) of extraction methods
| Method | Mechanism | Advantages | Disadvantages | Example(s) |
|---|---|---|---|---|
| Conventional extraction | The law of similarity and inter-miscibility | Simple in principle and easy to operate | Time consuming and large volume of solvent required | Saafi et al. (2009) |
| Ultrasonic-assisted extraction (UAE) | Implosion of cavitation bubbles when ultrasonic is applied causing surface peeling, erosion, and particle breakdown to release more phenolic compounds | Short operation time, low in cost, small volume of solvent required | Heat generated during extraction may cause phenolic compound decomposition | Chemat et al. (2017); Wei et al. (2010) |
| Reflux extraction | Reflux extraction extracts and concentrates the solvent simultaneously. During the extraction process, the solvent in the extraction tank is pumped out into the concentration tank. In the concentration tank, the solvent will be heated until evaporated then condensed and pumped back into the extraction tank. After repeating this process, the extracts in solvent will be accumulated | Short operation time, small volume of solvent required, lower fixed investment | Heating during evaporation process may cause phenolic compound decomposition | Habchi et al. (2021); Kongkiatpaiboon and Gritsanapan (2013); Sultana et al. (2009) |
| Microwave-assisted extraction (MAE) | Using microwave energy to heat solvents containing samples, thereby partitioning phenolic compounds from a sample matrix into the solvent | Short operation time, lower requirement for space, time, and solvent | High energy cost, the heat generated during applying microwave may cause phenolic compound decomposition, require extra consideration of the sample size | Chen et al. (2007); Hao et al. (2002); Hemwimon et al. (2007); Pan et al. (2002) |
| Soxhlet extraction | Soxhlet extraction is a modified analytical extraction method based on reflux extraction using a specific extractor called the Soxhlet extractor, which can be used for distillation purposes | Short operation time, small volume of solvent required, easy to operate, suitable for initial and bulk extraction | Heating during evaporation process may cause phenolic compound decomposition | Alara et al. (2018); Aspé and Fernández (2011); Ouahida et al. (2016) |
| Pressurized liquid extraction (PLE) | Solid sample is packed into a steeled container with extraction solvents then extracted for 5 to 15 min under high temperature and pressure | Shorter operation time, small volume of solvent required, good repeatability | Heating during extraction process may cause phenolic compound decomposition | Ju and Howard (2003); Alonso-Salces et al. (2001) |
| Supercritical fluid extraction (SFE) | Applying supercritical fluid like supercritical carbon dioxide as its solvent for phenolic compound extraction | Low operation temperature, high selectivity, inertness nontoxic | High requirement for co-solvent selection in phenolic compound extraction; high cost | Vatai et al. (2009); Ashfaq et al. (2021); Vuong et al. (2010) |
| Pulsed electric field extraction (PEF) | Applying short, high voltage pulses to destroy membrane structures and release more phenolic compounds into solvents | Short operation time, low operation temperature | The membrane changes are reversible, air bubbles make the process less effective, and the efficiency of the method depends on electric field strength and electrode gap | Liu et al. (2018); Joannes et al. (2015) |
| Enzyme-assisted extraction (EAE) | Enzymes like cellulase can decompose cell membranes which are mainly formed by macromolecules polysaccharides and proteins to increase the content of phenolic compounds released to solvents | Low operation temperature | Long operation time, hard to control, impurities may be also released during extraction | Hai et al. (2016) |