Urea Complexation for Docosahexaenoic Acid Enrichment from Crypthecodinium cohnii Oil: Using Water as the Urea Solvent.

Based on the observation that urea, water, and ethyl esters (EE) can form gypsum-like mixtures, this study explored the feasibility of employing water as a solvent for urea in the urea complexation method to enrich n-3 polyunsaturated fatty acids with docosahexaenoic acid (DHA)-containing ethyl esters (DHA- EE) from Crypthecodinium cohnii as the material. Under the conditions of a urea/DHA-EE ratio of 3, a water/DHA-EE ratio of 0.75, a mixing temperature of 65℃, and a cooling temperature of 20℃, a concentrate containing over 90% DHA was achieved. This demonstrated that using water as a solvent for urea, instead of polar organic solvents, is feasible and efficient for enriching DHA in urea complexation process.