Qualitative Changes of Cold Smoked Clarias gariepinus at Ambient and Cold Storage Conditions

Fish is a highly perishable product and major causes of spoilage are autolysis, bacterial decomposition and oxidative rancidity in fatty fishes. One of the cheapest form of fish preservation is smoking. Although deteriorative changes occur after smoking, the need to further freeze to extend the shelf life of the fish product is therefore expedient. Deteriorative changes and shelf-life of cold smoked Clarias gariepinus were studied at ambient temperature and under cold storage temperature of -250c for a period of twelve weeks. The organoleptic analysis, chemical analysis: peroxide value (P.V); free fatty acids (FFA) and total volatile base (TVB) and bacterial count/flora isolation were studied to determine the rate of spoilage. A total of sixty (60) live samples of Clarias gariepinus, average weight 200-300 g and cold smoked for 18 hours at a temperature of 300C were used for this experiment.

significant differences (P<0.05) were found in proximate composition values of fresh, cold smoked and fish stored for twelve weeks. The chemical assessment and bacteriological parameters also differed significantly. Higher values were recorded for all measured parameters at ambient temperature as compared to cold storage temperature of -250c. There was an increase in the crude protein (C.P) level due to loss of moisture during smoking. Fat content increased as a result of gradual oxidative rancidity of poly unsaturated fatty acids from zero weeks of initially smoked Clarias gariepinus to the 12th week. Total Volatile Base-Nitrogen values, Peroxide values (PV), Free Fatty Acid and Bacterial count values also increased.

Seven (7) species of bacteria were identified from the cold stored cold smoked fish while nine (9) species were identified at the ambient stored smoked fish, this showed that spoilage condition is faster in ambient storage rather than in the cold storage. There was significant difference (P<0.05) in the number of bacteria isolated under ambient condition (9 species) and cold storage (6 species) cold smoked Clarias gariepinus. Based on this, there is need for further cold storage of cold smoked Clarias gariepinus in order to increase its shelf-life.