Fatty acids composition in South African fresh water fish as indicators of food quality for human consumption
ABSTRACT Lipid classes and fatty acid composition (nutritive quality) of three commercially important fresh water fish species Oreochromis Mossambicus (Mozambique Tilapia), Clarias Gariepinus (Sharptooth Catfish) and Cyprinus Carpio (Carp) obtained from an aquaculture, different river systems and fish markets in South Africa were investigated. Fish fillets were prepared in the laboratory and used as representative samples for extraction of lipids through the Folch extraction method (using chloroform methanol at the ratio of 2:1). The structural separation of esterified fatty acids from fish lipids was conducted using gas chromatograph. Identification of fatty acids (FAs) composition was done by comparing the retention times of samples with the ones for all FAs standards and by spiking with commercially available fatty acids standards. Total lipid content of Tilapia fish was higher than that of Cat and Carp fish. Palmitic acid (16:0) was found to be the most abundant fatty acid (18.24 to 21.84 %) in all analysed fish species. Appreciable quantities of essential polyunsaturated fatty acids such as docosahexaenoic acid DHA (22:6 n-3, 3.92 to 6.16%), eicosapentaenoic acid EPA (20:5 n-3, 1.91 to 2.92 %) and Arachidonic acid (20:4 n-6, 7.19 to 8.50 %) were also found. EPA + DHA values were much higher on Tilapia fish lipid fractions in comparison with other fish lipid fractions. Observations showed that fish species from Gauteng province were the richest in lipid fractions as compared to those from other provinces. Of all fish species, cultured fish were found to be highly characterised by high levels of FAs as compared to the fish species collected from the river systems. This could be attributed to the FAs composition of their diet. The study points out that all fish species under study contain appreciable levels of n-3 polyunsaturated fatty acids and would therefore be suitable for highly unsaturated low-fat diets.