3.2. Optimization of extraction
A lot of methods have been applied for the extraction of fatty acids, such as soxhlet extraction [34,35], supercritical fluid extraction [36,37] and ultrasonication extraction [28,35]. Though most of the conventional methods are in common with soxhlet extraction, they are time-consuming and require large amount of solvent. Supercritical fluid extraction is very popular in recent years because it is non-toxic and environmental friendly. However, the system is complicated and expensive. Recent study indicated that extraction yields of supercritical CO
extraction was the lowest compared with other methods [36]..