Biochemical factors involved in the resistance of some smoked tropical fish samples to insect attack

Authors: AKINOLA JOHN AKINTOLA, OLUWATOYIN LAWAL

Abstract: The role of mineral elements (ppm), protein and oil content (%), and saponification and free fatty acid values in contributing to resistance against insect infestation was investigated in 4 fish species: Clarias gariepinus, Parachuma obscura, Hydrocynus sp., and Malapterus electricus. Smoked fish samples were purchased from a local market in Ilorin, Kwara State, Nigeria, packaged, and maintained at 4 ^°C for 7 days. They were later brought out to acclimatise, and then observed for 4 months for possible natural insect infestation. Next, crushed samples of each species were analysed using conventional chemical analysis in order to assess the role of some elements and biochemical compounds in inducing resistance. The results showed that insect infestation did not occur after the period of storage (4 months) and chemical analysis showed that 3 samples lacked lead (Pb), a heavy metal not required in trace amounts, but contained other heavy metals required in trace amounts, such as Fe, Mn, Co, and Cu. Protein content in the 4 samples was average (50%), but oil content was low. Hydrocynus sp. and Malapterus electricus had an acid value below 50 mg KOH/g. Additionally, all the samples had high a saponification value (above 500 mL/g). The presence of iron (>=1.5), high protein (%) and saponification values, low oil content, and low acid values of between 35 and 90 were the elements and biochemical constituents that prolonged the shelf life of the fish species studied.

Keywords: Acid value, fish, infestation, mineral content, resistance, shelf life

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