A study of the composition of fish liver and body oil triglycerides

Silver-ion high-performance liquid chromatography (Ag⁺-HPLC) was used to study the range and variations in molecular species of triglycerides from industrial, retail and laboratory extracted fish oils. These were contrasted with a typical plant oil. Selected fish oils were fractionated and the fatty acid distribution of the fractions determined by gas-liquid chromatography. Fish oils gave a characteristic Ag⁺-HPLC profile, typified by sharp, intense peaks at the start of the chromatogram and broad, multiple nongaussian peaks for the late eluting components. Triglycerides ranging from those that were wholly saturated to those containing 16 double bonds were isolated. Cod (Gadus spp.), saithe (Pollachius virens) and monkfish (Squatina squatina) liver oils gave similar triglyceride profiles. Mackerel (Scomber scombrus), capelin (Mallotus villosus) and herring (Clupea harengus) body oils gave characteristic triglyceride profiles which were associated with high concentrations of 20∶1 and 22∶1 fatty acids. Only small amounts of these particular triglycerides were observed for menhaden (Brevoortia spp.), South African anchovy (Engraulis capensis) and Indian sardine (Sardinella longiceps) oils, all of which contained minor amounts of these acids. The latter oils contained highly unsaturated triglycerides, whereas only traces of these were noted for the former. Chromatography with Ag⁺-HPLC can be used for the rapid screening of fish oils and for selecting those oils rich in polyunsaturated acids that may be suitable for enrichment. Cottonseed oil gave well-defined and discrete peaks. Similar peaks were observed in the chromatogram of Omega-combination, a mixture of primrose and fish oils. Thus, fish, plant and a mixture of these oils can be readily distinguished.