3 EXTRACTION METHODS FOR DETERMINATION OF LIPIDS IN FISH-MEAL - EVALUATION OF A HEXANE ISOPROPANOL METHOD AS AN ALTERNATIVE TO CHLOROFORM-BASED METHODS

Three different extraction methods were compared for the determination of lipids in both oxidised and antioxidant-stabilised brown fish meal . The three methods under investigation were those of Smith-Ambrose Kn obl using chloroform/methanol/water, Bligh and Dyer also using chlorof orm/methanol/water but monophasic, and Hara and Radin using hexane/iso propanol. The fat content, determined gravimetrically, was significant ly lower (P < 0.05) when hexane/isopropanol was used for lipid extract ion from both oxidised and antioxidant-stabilised fish meal, than when either of the chloroform systems was used. Determination of lipid cla sses in the lipid extracts using silica gel thin-layer chromatography on Chromarods-SIII, with flame ionisation detection by Iatroscan, sugg ested that the lower lipid recovery by the hexane/isopropanol method m ay be due to a less effective extraction of the more polar lipid class es, including oxidation products, present in brown fish meal.