Temperature and pressure effects on supercritical carbon dioxide extraction of n-3 fatty acids from red seaweed

Lipids were extracted with supercritical carbon dioxide (SC-CO2) from a subtropical red seaweed (Hypnea charoides) within the temperature range 40–50°C and the pressure range 24.1–37.9 MPa. In general, the extraction rates of algal lipids increased with pressure and temperature except when the pressure was at 24.1 MPa. The combined effect of pressure and temperature on the solubility of individual n-3 fatty acids in the SC-CO2 varied with its carbon chain length. The concentrations of C18, C20 and C22 n-3 fatty acids, extracted under different pressure and temperature conditions, were significantly different (p<0.05). Proportions of total polyunsaturated fatty acids increased significantly (p<0.05) and proportions of total saturated fatty acids decreased significantly (p<0.05) with increasing pressure as shown by the saturated/unsaturated and saturated/polyunsaturated ratios.