Supercritical fluid extraction of carotenoids and chlorophylls a, b and c, from a wild strain of Scenedesmus obliquus for use in food processing

Faster and more selective extraction methods are urged to recover food-grade pigments and antioxidants from microalgae – which do not resort to food-incompatible and environment-unfriendly solvents. Hence, this study ascertained the influence of pressure, temperature, CO2 flow rate and a polar co-solvent upon the yields of carotenoids and chlorophylls in supercritical fluid extraction of Scenedesmus obliquus biomass. The highest carotenoid yield was attained at 250 bar and 60 °C. The yields of chlorophylls, when using plain CO2, increased slightly with pressure, but decreased with temperature and CO2 flow rate; the highest yield of chlorophyll a   was at 4.3gCO2min-1, whereas ethanol as co-solvent increased all yields except that of chlorophyll c. The highest ratio of total carotenoids to chlorophyll a was reached at 250 bar and 60 °C. A remarkable selectivity was observed under these operating conditions, which may enable easy separation and purification of the aforementioned pigments.

► Extraction of high added-value additives from microalgae for food formulation is of strong interest. ► Supercritical fluid extraction is more suitable than common liquid extraction, but still expensive. ► Optimization of operation conditions is a must for economically feasible processes.