ABSTRACT
Information on the chemical composition of fish is vital, as the nutritional and medicinal value of fish products depends on their proteins, lipids, minerals and vitamins content. This study was aimed at investigating the effects of oven drying and smoke drying on the nutritional composition of captured Clarias gariepinus (Burchell, 1822) and Tilapia zilli (Gervais, 1848) from Ikpoba Reservoir, Benin City, Edo State.
Samples of C. gariepinus and T. zilli were collected from February to September 2018 from Ikpoba Reservoir with the assistance of fishermen at the landing sites using fishing traps, cast and gill nets of various mesh sizes. Routine measurements of standard length, total length and body weight were taken and the fish samples were divided into three batches. Batch I had fresh fish samples, Batch II samples were oven-dried while Batch III samples were locally smoked-dried. The proximate composition (moisture, fat, ash, protein and non-fat extract) and mineral content (sodium, potassium, calcium, magnesium, iron and zinc) of C. gariepinus and T. zilli were determined using the standard methods of the Association of Official Analytical Chemists (AOAC).
Results showed that oven drying and smoke drying had effect on the proximate and mineral composition of the two fish species. High moisture content was recorded in fresh samples of C. gariepinus (71.12%) and T. zilli (76.41%), while smoked samples recorded the least values of 5.03% and 5.56% respectively. The mean percentage fat was highest (6.85%) in fresh samples of C. gariepinus and lowest (0.61%) in smoked samples of T. zilli. Protein content of C. gariepinus (16.87%) and T. zilli (16.25%) in oven-dried samples were higher than the values recorded in fresh (15.51% and 13.41%) and smoked (14.95% and 11.98%) samples. Ash content was highest (6.41% and 6.54%) in smoked samples and lowest (1.91% and 4.48%) in fresh samples of C. gariepinus and T. zilli. Non-fat extract (69.25% and 75.69%) content in smoked samples were higher than the values recorded in oven-dried (63.29% and 65.69%) and fresh (6.86% and 13.96%) samples. The order of mineral content in C. gariepinus was sodium > potassium > calcium > iron > magnesium > zinc, and in T. zilli iron > potassium > sodium > calcium > zinc > magnesium was recorded. Highest content of sodium, potassium and magnesium were recorded in smoked samples, while oven-dried samples recorded highest content of calcium, iron and zinc in both C. gariepinus and T. zilli. In this study, C. gariepinus and T. zilli from Ikpoba Reservoir are of good nutritional quality based on their protein content, and their consumption (fresh and oven dried) as a first choice protein for humans is recommended. Furthermore, the oven dried samples presented the best form of the fish for human consumption. It is therefore recommended that the traditional method of smoke drying should be discouraged and the local fish farmers provided with oven dryers for use in fish processing.
