ASSESSMENT OF PHYSICAL AND CHEMICAL CHANGES IN SOME FROZEN FRESH WATER FISHES DURING STORAGE

Abstract

Chemical and physical changes in some fresh water fish species; Clarias gariepinus (Burchell 1822), Oreochromis niloticus (Trewavas 1983) and Heterotis niloticus (Cuvier 1829) were investigated under low temperature (_4°C to-IODC) storage conditions in a deep freezer (Mondial frigor) for 7 weeks (49 days). The fish samples were analyzed for proximate composition at the beginning and at the end of the storage period to determine the nutritive changes in fish muscle. The fish were assessed for quality changes using some organoleptic and chemical methods. The organoleptic assessment was based on changes in texture, odour, skin pigmentation, gill tint, eye shape and skin mucous of the fish species using hedonic scale. Weekly chemical assessment was based on changes in total volatile nitrogen (TVN), crude protein, lipid content, peroxide value and pH. The physical assessment showed that the three species of fish kept well for 35days. However, there was a significant difference (P<0.05) in changes in physical attributes among the different species of fish. The result of chemical evaluation of the stored fish species showed that there were significant difference (P< O.05) in chemical indices among the different species during storage. However, peroxide value in the fish muscle remained undetectable over the period of storage. The study showed that all the indices measured (physical and chemical parameters), except peroxide value, changed significantly with storage.