Abstract
Post-harvest loss of fish is a major factor of economic and protein wastages in the developing countries. In this study, the effects of two common methods of preservation, smoking and freezing on the nutritive value of the African mud catfish, Clarias gariepinus were determined. Live samples of C. gariepinus were obtained from the fish farm of the Department of Environmental Biology and Fisheries, Adekunle Ajasin University, Akungba-Akoko, Ondo State, Nigeria, and were transported to the laboratory of the Department. One portion of the harvested fish was smoked, using a smoking kiln (model: ELC 1600) at 60-70 oC for 24 hours and stored in a polythene bag for further use. Another batch of C. gariepinus was preserved immediately after harvest in the freezer (Haier Thermocool, BD-428A) at less than -0 oC for 20 days. The third batch of the live fish was sacrificed immediately and prepared for biochemical analysis. The proximate compositions of the fish samples were determined according to AOAC (1995). The percentage moisture, protein, lipid, ash, crude fibre and carbohydrate contents obtained in the smoked fish samples were statistically different (P > 0.05) to the fresh fish samples (control). Similarly, there were significant differences in the percentage protein, lipid and crude fibre values in the frozen fish samples when compared to the fresh fish samples but there were no significant changes (P < 0.05) in the moisture, ash and carbohydrate contents of the frozen fish samples in comparison to the control. The proximate values of the frozen fish evoked significant differences in comparison to the smoked samples except in the crude fibre and lipid contents. Phosphorous content was highest in the smoked fish samples and lowest in the fresh fish samples while the values of iron, potassium and vitamin C contents were generally low in all the samples. Smoking demonstrated a better efficient method of fish processing in terms of the retention of protein value and reduction in the moisture content. The information obtained in this study could be useful to fish consumers, processors and nutritionists in the efficient management of fish resources.
Highlights
Fish are highly nutritious and provide animal proteins that consist of all the essential amino acids in relatively high concentrations, low in cholesterol and saturated fats, and are rich in key fatty acids, minerals and vitamins (Murray & Burt, 1991)
Phosphorous content was highest in the smoked fish samples and lowest in the fresh fish samples while the values of iron, potassium and vitamin C contents were generally low in all the samples
The moisture (5.885 ± 0.034), protein (32.728 ± 0.573), crude fibre (1.036 ± 0.119) and carbohydrate (5.169 ± 0.966) contents of smoked fish samples were found to be significantly lower in comparison to the respective values found in fresh fish samples
Summary
Fish are highly nutritious and provide animal proteins that consist of all the essential amino acids in relatively high concentrations, low in cholesterol and saturated fats, and are rich in key fatty acids, minerals and vitamins (Murray & Burt, 1991). Fish has the potential to be considered as a balanced food and can be expected to provide relief from malnutrition (Ogundiran, Adewoye, Ayandiran, & Dahunsi, 2014). It has a high economic value for many countries because it represents the largest share among agribusiness products on the global market (Silva, Silva, Andradel, Veloso, & Santos, 2008). There could be a high risk of heavy metal bioaccumulation, such as, mercury in certain fish species if mercury is released from the air (where it naturally occurs) or through industrial pollution and accumulates in streams and oceans (Smith, 2012; Guedenon, 2012)
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