In the extraction process of solvent extraction method, the concentration of solvent, material-liquid ratio, extraction temperature and extraction time will directly affect the extraction rate of active ingredients.Cristina Juan et al. extracted ochratoxin A from rice by solvent extraction method and determined the content of OTA by fluorescence detection and liquid chromatography.The study showed that at the optimum material-liquid ratio, extraction temperature and extraction time, the highest content of OTA in the extract was 4.17 ng/g. Monte D. Holt et al. used solvent extraction to extract alkylresorcinol from raw and cooked wheat seeds and showed that the extraction time could be saved by using solvent extraction method.
Ultrasonic extraction uses the strong vibration and cavitation effect of ultrasonic waves to accelerate the release, diffusion and dissolution of substances from plant cells into the solvent, while keeping the structure and biological activity of the extracted substances unchanged. The principle of ultrasonic extraction is mainly a physical process, and is a relatively new extraction method that has been gradually gaining attention in recent years. For most of the components, ultrasonic extraction method can significantly shorten the extraction time, consume less solvent and have high leaching rate than the conventional solvent extraction, so it has high extraction efficiency.
In the mid-1980s, supercritical CO2 extraction was gradually applied to the extraction and separation of active ingredients of plants, and it is a new technology that has been successfully studied and applied. Monica Waldeb.ck et al. used pressurized fluid extraction technique to extract squalene and α-tocopherol from olives, and the results showed that the best extraction effect was achieved when the solvent was ethanol, the extraction temperature was 190°C, and the extraction time was 10 min. The effect of extraction pretreatment and extraction process conditions on the yield was mainly investigated. The experimental study showed that the highest extraction rate was achieved when the particle size was 30 nets, the pressure was 4000-5000 psi, the extraction temperature was 40-50°C, and the CO2 fluid flow rate was 2.0 mL/min.
Microwave-assisted extraction technology (microwave.assistedextraction, MAE) is a new technology that uses microwave energy to improve extraction efficiency. Microwave assisted extraction is the use of microwave heating characteristics of the material in the target components of the selective extraction method, by adjusting the parameters of the microwave, can effectively heat the target components to facilitate the extraction and separation of target components. The principle of microwave-assisted extraction method for plant extraction is that the plant sample absorbs a large amount of energy in the microwave field, while the surrounding solvent absorbs less, thus generating thermal stress inside the cell, the plant cell ruptures due to the thermal stress generated inside, so that the material inside the cell directly contacts the relatively cold extraction solvent, which in turn accelerates the transfer of the target product from the inside of the cell to the extraction solvent, thus enhancing the extraction process. The microwave-assisted extraction method technically uses thermal energy as well as immersion and filtration, but extracts plant extracts much faster than traditional methods, reducing extraction time while avoiding the destruction and degradation of valuable plant extracts.
E. BARZANA et al. used enzyme extraction method to extract carotenoids from Marigold. The effects of feed-liquid ratio, enzyme concentration, enzymatic time and temperature on the extraction rate were mainly investigated, and the results showed that the optimal extraction process was: feed-liquid ratio of 1:4, enzyme concentration of 0.3%, extraction time of 1.5h and temperature of 25°C. Zhang Xiaoqing et al. used the enzyme extraction method to extract the active ingredient-flavonoids from Ginkgo biloba, and found out the optimal process conditions of enzyme concentration, pH, enzyme digestion temperature and time that affect the extraction rate by orthogonal experiment.