Nutritive value of fresh and brackish water catfish as a function of size and processing methods

Abstract

Catfish (Clarias gariepinus) of different sizes (small, 30.33–30.83 cm and 191.67–195.00 g; medium, 36.67–37.50 cm and 275.00–303.33 g; large, 41.33–49.67 cm and 536.67–726.00 g) collected from brackish (Igbokoda) and fresh water (Ogbese) bodies was subjected to different treatments (fried, boiled with/without salt solution and roasted). The proximate (ash, fat and protein) and mineral (Ca, Zn, Fe, Mg, P and I) compositions of all the treatments were determined. The highest protein concentrations (on a dry weight basis percent) (Ogbese, 73.25; Igbokoda, 72.52) of fish samples were recorded by boiling with water, while the ones roasted recorded the lowest values of 57.51 and 58.33%, respectively. The iodine level (grams of I per 100 g) in the flesh of fish varied with size, treatment and location; it increased with size, was reduced by some treatments (boiling with either water or NaCl solution), while frying and roasting had the highest level compared with boiling. The lowest iodine concentrations were 93.45 (Ogbese fish boiled with NaCl solution) and 160.94 (Igbokoda fish boiled with either water or NaCl solution). On the whole, Igbokoda brackish water fish (160.94–314.08) had a higher iodine content than Ogbese fresh water fish (93.45–205.06) with the highest concentration in fried and roasted fish samples (205.06, 314.08) in Ogbese and Igbokoda water bodies, respectively. Higher mineral compositions were also found in the brackish water fish (for flesh and serum), and also increased with size and were reduced by some treatments (boiling and frying) in the flesh of fish samples. The fish (catfish) from the brackish water body appeared to be more nutritious than that from the fresh water body. The highest protein values were recorded by boiling with water, while frying and roasting gave the highest iodine value. Moreover, the study revealed that size is a factor to be considered by the population dependent on fish as a source of protein, iodine and other vital elements.