Biochemical and organoleptic changes in some frozen commercially important freshwater fish species in Benin metropolis, Edo state, Nigeria

Abstract

This study assessed the biweekly comparative changes in the organoleptic and biochemical composition of Nile Tilapia, Oreochromis niloticus, Electric fish, Malapterurus electricus, African knife fish, Xenomystus nigri and Snake fish, Erpetoichthys calabaricus. The Fish samples were procured live from the Ikpoba River in Benin metropolis, Edo State, Nigeria. They were transported to the laboratory, killed, degutted, washed and frozen. Organoleptic assessment with the aid of questionnaire on the basis of eyes, gills, skin and flesh quality was conducted by five (5) trained panelists. The proximate composition was assessed using changes in Moisture, Ash, Protein and Fat contents. Biochemical indices carried out were changes in pH, Total Volatile Base (TVB), Trimethylamine Acid (TMA), Free Fatty Acid (FFA) and Peroxide Value (PV) levels. The data were subjected to Analysis of variance and the means were tested and compared using Duncan multiple range test at 5% level of significance. Organoleptic assessment revealed that there were no significant (p > 0.05) changes in the fish samples during the course of storage. The proximate changes showed that the percentage moisture content of the fish samples increased and that of crude protein decreased but were not significantly different. Crude fat as well as Ash content decreased significantly (p < 0.05) during the time of storage. In general, pH, PV, TMA, FFA as well as TVB increased significantly (p < 0.05) with increase in storage period but the fish samples were all within the limits of acceptability. The levels of these parameters with respect to storage temperature and time may be exploited to minimize the incidence of fresh fish food poisoning and post-harvest losses.

Keywords: Organoleptic assessment, chemical composition, Oreochromis niloticus, Malapterurus electricus, Xenomystus nigri, Erpetoichthys calabaricus