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Advances in Applied Biotechnology Part 7

Tham khảo tài liệu 'advances in applied biotechnology part 7', khoa học tự nhiên, công nghệ sinh học phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | Biological Activities and Effects of Food Processing on Flavonoids as Phenolic Antioxidants 109 Fig. 4. Flavonoid structural elements necessary for biological activity the presence of structural elements promotes the cited activity - the presence of structural elements reduces the cited activity. 110 Advances in Applied Biotechnology 2.3 Extraction of flavonoids Extraction is the most important step in the development of analytical methods for plant extracts analysis. A summary of experimental conditions of the extraction methods is reported in Table 3. Basis unit operations of extraction is often the plant drying and its milling to obtain an homogenous powder and improve the extraction kinetic of the molecules. Methods as sonication heating under reflux extraction with Soxhlet apparatus are the most used Ong 2004 . However these methods are often long and need large volumes of organic solvents with low extraction rates. Molecules we want to extract can be polar non-polar or heat sensitive thus the extraction method must take all these parameters into account. To reduce the use of organic solvents and to improve the extraction rate other methods such as extraction assisted by microwave supercritical extraction accelerated extraction by solvents the pressurized liquid extraction the pressurized extraction by hot water and the pressurized extraction by hot water associated to surfactants were introduced to the phenol extraction from plants. These different techniques were summarized in Table 3. Extraction method Solvents Temperature C Pressure Time Sonication Methanol Ethanol Mix alcohol water Can be heated 1 h Soxhlet extraction Methanol Ethanol Mix alcohol water Depending on the solvent used 3-18 h Microwave extraction Methanol Ethanol Mix alcohol water 80-150 Depending on the extraction container 10-40 Extraction by supercritical fluid Carbon dioxid Mix carbon dioxid Methanol 40-100 250-450 bar 30-100 min Extraction by accelerated solvent Methanol 80-200 100 bar .