Mackerel processing waste comprising skins, viscera, and muscle tissue was evaluated for concentrating PUFA by urea complexation. Fish oil was extracted using either chloroform/methanol (2∶1, vol/vol) or hexane/isopropanol (3∶2, vol/vol). The yield of oil, as well as iodine, peroxide, and acid values, was determined for fresh fish oil extracts, and oil samples were storel at −70°C in the presence of 100 ppm α‐tocopherol. PUFA concentrates were prepared from saponified fish oil. The mean oil yields were 9.18±2.3, 9.2%±2.4, and 38.1±3% for viscera, muscle, and skin, respectively. The mean baseline iodine value was 134±5, which increased to 296±7 after urea complexation. It was possible to concentrate PUFA from mackerel processing waste. The type of tissue used did not affect the amount of PUFA concentrated. Mackerel skin was most desirable because of its high oil content.

n-3 PUFA (omega-3 polyunsaturated fatty acid) concentrate from mackerel oil enriched in EPA (eicosapentaenoic acid) and DHA (docosahexaenoic acid) was used to esterify isomers of CLA (conjuated linoleic acid) to produce acylglycerols (glycerides). Catalysis was potentiated by immobilized lipases from the yeast Candida antarctica and the mould Mucor miehei. C. antarctica lipase showed higher reactivity and much faster initial rate of incorporation of CLA into acylglycerols than its M. miehei counterpart. Synthesis with molecular sieves also achieved a better rate of incorporation of fatty acids into acylglycerols than using vacuum or systems without water removal. Esterification achieved at 40 degrees C with C. antarctica lipase was significantly different from that achieved at 60 or 50 degrees C. However, there was no significant (P<0.05) difference between esterification at 50 degrees C and 60 degrees C. The molar ratio of glycerol to fatty acid was found to influence the initial rate of incorporation, with the lower ratios showing higher initial rates compared with the higher ratios. The present study shows that direct esterification is an effective mechanism for producing acylglycerols from fatty acids in a controlled system.