Nutritional quality of fish oil extracted from selected freshwater fish species

Abstract

There is increased consumer awareness of the nutritional importance of fish oil consumption in recent time, however there is paucity of information on the quality of oil obtained from freshwater fishes available in this study area. Nutritional quality of fish oil extracted from 9kg each of Chrysichthys nigrodigitatus, Synodontis membranaceous and Clarias gariepinus were investigated with the aim of providing baseline information on the nutritional quality of oil in the fish available around the study area. Wet rendering, soxhlet extraction and microwave assisted extraction methods were used. Data collected were subjected to appropriate statistical analysis using SPSS 6.0. version. S. membranaceous have the largest oil yield while C. nigrodigitatus have the lowest oil yield; wet rendering oil extraction method gave the highest oil yield. The physical quality characteristics of S. membranaceous was the best with the lowest melting point (28.73 ±0.39°C), specific gravity (0.11± 0.01) and refractive index (1.14 ±0.01) while C. gariepinus oil had the poorest physical quality characteristics. Oil of C. nigrodigitatus have better chemical qualities than the rest having the lowest saponification value (9.81±0.01 mg KOH/g), iodine value (1.59±0.01 gl/100g), acid value (1.12±0.01 mgKOH/g) and free fatty acid (0.56±0.01%) while C. gariepinus oil was the poorest. C. nigrodigitatus also have the highest polyunsaturated fatty acid (PUFA) (18.75), highest Ʃn-3 FA (23.45), highest DHA (Docosahexaenoic acid) (4.93), highest eicosapentaenoic acid EPA+DHA (7.8). The oils chemical qualities are in the order of C. nigrodigitatus> S. membranaceous> C. gariepinus and are of good quality. Oil obtained from C. nigrodigitatus is therefore recommended due to its good chemical qualities using wet rendering oil extraction method. Information provided in this study will guide industrialists and nutritionists on the best extraction method and fish that will give highest oil yield and best oil quality in the study area.