INFLUENCE OF FROZEN PERIOD ON THE PROXIMATE COMPOSITION AND MICROBIOLOGICAL QUALITY OF NILE TILAPIA FISH (<i>OREOCHROMIS NILOTICUS</i>)

Abstract

ABSTRACT The rationale of the study was to investigate the influence of frozen period on quality of fish fillet. The proximate composition and microbiological analyses were carried out at 15 days interval on tilapia fish fillets during frozen storage. It was found that the protein, moisture and ash contents decreased significantly (P < 0.05) during the entire storage period. However, the fat content increased from 0.37 ± 0.01 to 0.56 ± 0.01 g/100 g of fillet. The total volatile bases nitrogen and pH values also increased significantly The total bacterial load in fresh fillets was reduced from 2.57 × 106 to 8.2 × 105 cfu/g after 90 days of frozen storage. The total coliforms decreased from 460 to 23 MPN/g and the fecal coliforms decreased from 23 MPN/g to undetectable level, respectively. Thus, a significant quality loss was observed for tilapia during storage. However, the present frozen conditions retained the fish material under acceptable microbiological conditions for human consumption. PRACTICAL APPLICATIONS The main challenge that fish industries face in developing countries like Ethiopia is to comply with consumer expectations, particularly on product quality. The quality of fresh fish is one of the key factors that govern the shelf life of the final product at low temperature preservation. The Ethiopian fish production and marketing enterprise is vested with the responsibility of inland fisheries processing and marketing. The enterprise, without any scientific basis, labeled the frozen tilapia fish shelf life to be 9 months. Therefore, the aim of this study was to investigate the low-temperature (−18C) preservation technique practiced by the enterprise in order to evaluate the influence of frozen period on quality of a fish fillet. The results on changes in proximate composition and microbial load of Nile tilapia fish fillet enabled to determine the frozen period of a fish fillet that can be fit for human consumption devoid of deterioration. The results can also be used for further investigation and detailed research is required to help commercial processors beyond 90 days of frozen storage.