Microbiological and Chemical Changes of Nile Tilapia (&lt;em&gt;Oreochromis niloticus&lt;/em&gt; L.) Fillet during Ice Storage: Effect of Age and Sex

Alemu Lema Abelti

doi:10.19026/ajfst.5.3093

Abstract

Fish is one of the most highly perishable food products. The aim of this study was to investigate microbiological and chemical changes of Nile tilapia fillet during ice storage. Nile tilapia samples were collected from Lake Zeway, Ethiopia. The fillet was stored at 0°C for 30 days on ice. Total plate count, total and fecal coliform, total volatile base nitrogen and pH was measured at the interval of four days. Regardless of age and sex, Total plate count varied between 4 to 11.74 log cfu/g. Total coliform counts fluctuated between 1100 MPN/g. However fecal coliform changed between 23 to <3 MPN/g. Total volatile base- Nitrogen has increased from 7.5 to 42.0 mg N/100 g. Similarly, pH has increased from 6.1 to 7.6 during the ice storage period. The eventual increase observed in mean total plate count could be due to multiplication of organisms favored at the storage condition. The increased total coliforms may be attributed to fillet quality and temperature fluctuations. The increment in TVB-N during ice storage is associated with activity of micro-organisms during later stages of deterioration. The increase in pH values is due to the formation of basic decomposition products. Finally, Post mortem change of Nile tilapia fillet was noticed and bacterial metabolites like Total volatile base-nitrogen, Total plate count and pH were invariably increased throughout the storage time indicating that they are good parameters to predict shelf life.

Highlights

Fish is one of the most highly perishable food products
It is a general term which includes the measurement of trimethylamine, dimethylamine, ammonia and other volatile basic nitrogenous compounds associated with seafood spoilage
Hernández et al (2009) had reported the total aerobic mesophilic bacteria load of 11.2 log CFU/g for meagre stored on ice for 18th day of storage

Summary

Introduction

Quality deterioration of fresh fish rapidly occurs and limits the shelf life of the product. Most of the methods that have been used to estimate the quality of fresh fish measure or evaluate parameters that change, disappear or formed during deterioration of fish. These methods may be divided into several groups such as microbiological and chemical methods (Huss, 1995). Total plate count is good indicator of the sensory quality or expected shelf life of the product (Olafsdottir et al, 2006; Koutsoumanis and Nychas, 2000). TVB-N is good indicators for assessment of the freshness measurement of quality in such as ray fish (Ocaño-Higuera et al, 2011), Cazon fish (OcañoHiguera et al, 2009), industrial fish for meal and silage (Olafsdottir et al, 1997), Anchovies (Pons et al, 2006), Pacific saury (Sallam et al, 2007), Galda and Balda (Ali et al, 2010), Haddock and cod (Olafsdottir et al, 2006), Yellow grouper (Li et al, 2011), African cat fish (Adoga et al, 2010), Nile perch (Okeyo et al, 2009) and Nile Tilapia (Liu et al, 2010)

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