Combination of Urea Complexation and Molecular Distillation to Purify DHA and EPA from Sardine Oil Ethyl Esters

Urea complexation (UC) and the molecular distillation (MD) technique were applied jointly to purify eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) from sardine oil ethyl esters (SOEE). Response surface methodology (RSM) was used to measure the influences of the variables to the responses and the optimal conditions. Regression analysis and variance analysis of the models demonstrated that each multinomial correctly represented the relationships between the responses and the variables. The urea-to-SOEE ratio was much more significant than crystallization temperature in UC, and the quadratic term of rotation speed of swept-surface scrapers was the most significant variable in MD. Optimal UC conditions were 1.9:1 urea-to-SOEE ratio and -1 A degrees C crystallization temperature at which the purity and total recovery of EPA and DHA were 65.6 % and 46.8 %, respectively. The best conditions predicted for MD were 75 A degrees C distillation temperature, 54.8 A degrees C preheat temperature, 4.5 A degrees C condensation temperature, and 307 rpm rotation speed at which the purity of EPA and DHA was 83.5 %. The predicted values were verified to be reasonably close to the experimentally observed values.