One-Step Concentration of Highly Unsaturated Fatty Acids from Tuna Oil by Low-Temperature Crystallization

Highly unsaturated fatty acids (HUFA), including eicosapentaenoic acid (EPA, 20:5n‐3), docosapentaenoic acid (DPA, 22:5n‐3 and 22:5n‐6) and docosahexaenoic acid (DHA, 22:6n‐3), play an important role in human health and nutrition. In this study, concentration of HUFA in free fatty acids (FFA) form by low‐temperature crystallization was investigated. For this purpose, tuna oil (7.1% EPA, 26.8% DHA) was first converted into corresponding FFA. Subsequently, crystallization conditions of various solvent types, the ratio of FFA to acetonitrile, operation temperature and crystallization time were optimized at a small scale of 2 g tuna oil fatty acids. Taking purity and yield into account, the optimum conditions were a 1:10 ratio of FFA to acetonitrile (w/v), ?60 °C, and 1 h. The optimal conditions resulted in concentrations of EPA, DHA and HUFA of 15.1, 58.4 and 79.6%, respectively, with corresponding yields of 61.5, 61.8 and 60.7%, respectively. Crystallization was carried out under the optimal conditions at a large scale of 200 g tuna oil FFA, and a similar concentration result was achieved. After evaporating away the solvent, the residual amount of acetonitrile met the US Pharmacopoeia requirement of <410 ppm. The process for enrichment of HUFA is readily scalable, effective and time‐saving.