MICROBIAL QUALITY OF FROZEN FISH SOLD IN UMUAHIA METROPOLIS

ABSTRACT

Microbial quality of frozen fishes obtained from three different markets were carried out using standard methods. The total viable count ranged from 1.2x104cfu/g to 1.9 x104cfu/g for Ndoro market, 1.4 x104cfu/g to 1.8 x104cfu/g for Orieugba and 1.2 x104cfu/g to 2.0 x104cfu/g for Ubani. Total fungi count showed their percentage occurrence of 6.6.7% (Ubani), 55.6% (Ndoro) and 55.6% (Orieugba). The bacteria isolated from fish samples were Staphylococcus, Proteus, Salmonella, Micrococcus, and E.coli specie, while fungi isolated were Aspergillus, Penicillum, and Yeasts. The study showed that the frozen fish samples were heavily contaminated which may be as result of poor sanitary practices employed by the vendors. This is of public health concern as these organisms are known causes of foodborne diseases.

TABLE OF CONTENTS

Title page                                                                                                                    i

Certification                                                                                                                ii

Dedication                                                                                                                  iii

Acknowledgements                                                                                                    iv

Table of contents                                                                                                        v

List of tables                                                                                                               vi

Abstract                                                                                                                      vii

CHAPTER ONE

1.0       INTRODUCTION                                                                                          1

1.2       Aims and objectives                                                                                       4

CHAPTER TWO

2.0     LITERATURE REVIEW                                                                                 5

CHAPTER THREE

3.0       MATERIALS AND METHODS                                                                   9

3.1       Source of materials                                                                                         9

3.2       Sampling and sample preparation                                                                  9

3.3       Media preparation                                                                                          9

3.4       Microbiological analysis                                                                                10

3.5       Determination of microbial flora                                                                    11

3.5.1   Characterization of bacteria isolate                                                                             11

3.5.1.1 Colony features                                                                                                           12

3.5.1.2 Microscopic features                                                                                                  12

3.5.1.3 Biochemical reaction                                                                                                  12

3.5.1.4 Sugar utilization test                                                                                       12

3.5.2    Characterization of fungi isolates                                                                   12

3.5.2.1 Colony feature                                                                                                            13

3.5.2.3 Structural features                                                                                                       13

3.5.3 Identification of isolates                                                                                                13

3.5.4    Determination of prevalence                                                                          13

3.6.      Statistical analysis                                                                                          14

CHAPTER FOUR

4.0       RESULTS                                                                                                       15

CHAPTER FIVE

5.0       DISCUSSION, RECOMMENDATION AND CONCLUSION                         20       

5.1       Discussion                                                                                                       20       

5.2       Recommendation                                                                                            22

5.3       Conclusion                                                                                                      23

References                                                                                                      24

            Appendix       

LIST OF TABLES

Table                Title                                                                   Page

1: Characteristics of bacteria isolates from frozen fish sold in Umuahia metropolis     16

2: Microbial enumerations in frozen fish sold in Umuahia metropolis.                          17

3: Occurrence of fungi isolates in frozen fish sold in Umuahia metropolis                                18

4: Occurrence of bacteria isolates in frozen fish sold in Umuahia metropolis              19

CHAPTER ONE

1.0        INTRODUCTION

Seafood has traditionally been a popular part of the diet and main supply of animal protein in many parts of the world. They are prone to contamination at various stages of handling and processing and the quality is a major concern to food processors and public health authorities (Gnanambal and Patterson, 2005). The Food and Agriculture Organization (1994) asserted that fish contributes about 60% of the world’s supply of protein and that 60% of the developing world derives more than 30% of their annual protein from fish. However, In Nigeria, fish constitute 40% of the animal protein intake (Olatunde, 1998). This implies that any shortfall in fish availability will affect the animal protein intake of people in tropical countries (Salawu et al., 2004).

Also in Nigeria the demand for fish is put at 2.10 million metric tonnes with fish imports making up to about three fifth (740,00 M T) of the fish supply (FDF, 2007). Majority of the frozen fishes are sold in the open markets. However, the ones sold in supermarkets are either imported frozen or those caught in Nigerian waters and frozen on board. (Ola and Akande 1996) reported on the quality of “Wet” fish in retailing markets in Lagos. (Arannilewa et al., 2005) noted that protein decreased with increasing duration of frozen storage with fresh samples not frozen having higher protein content. Disadvantages such as product dehydration, rancidity, drip loss and product bleaching have an overall effect on the quality of frozen food (Kropf and Bowers 1992).

In spite of some disadvantages associated with frozen storage freezing is accepted as effective way of preserving fish (Arannilewa et al., 2005). There is paucity of information on quality of fish sold in Nigeria markets. Due to paucity of information on quality of fish sold in supermarkets, the study was designed to examine the hygienic status of frozen fishes in some reputable supermarkets in Lagos state. In the study, the work reports on total plate count, organisms of public health significance and biochemical aspects for quality.

Seafood has traditionally been part of the human diet in many countries and is an important source of nutrients, especially of high digestible proteins (Faber et al., 2010). However, it is also known that seafood can be a source of food-borne toxin infections, which emphasizes the need of a thorough control of its bacteriological characteristics (Croci and Suffredini, 2003). 

A bacterial species associated with infection via ingestion of edible products of marine origin is Escherichia coli. The occurrence of this bacterium in food is directly related to fecal contamination. On what seafood is regarded, the occurrence of E. coli is related to water contamination and/or unhygienic conditions during the handling process (Huss, 1993). Often cited as potential cause for E. coli contamination are: The quality of the ice used for conservation (Vieira et al., 1997), and also the food processing plants (Bagge-Ravn et al., 2003). Escherichia coli is a commensal microorganism whose niche is the mucous layer of the mammalian colon. This bacterium is the most abundant facultative anaerobe of the human intestinal micro flora (Kaper et al., 2004). Furthermore, E. coli is widely distributed in the intestinal tracts of warm- blooded animals (Ishii and Sadowski, 2008). E. coli is often nonpathogenic, al- though different strains may cause diseases in gastrointestinal, urinary, or central nervous systems (Nataro and Kaper, 1998).

Currently, six categories of diarrheagenic E. coli have been acknowledged; enterotoxigenic E. coli (ETEC) (Dalton et al., 1999), enteropathogenic E. coli (EPEC), enteroinvasive E. coli (EIEC) (Levine, 1987), enterohemorrhagic E. coli (EHEC, Shiga toxin-producing E. coli or STEC), entero aggregative E. coli (EAEC or EAggEc), and diffusely adherent E. coli (DAEC) (Scaletsky et al., 2002). Despite not being very common, the isolation of diarrheagenic E. coli from seafood is reported. (Kumar et al., 2001) detected Shiga-toxigenic E. coli in fish and clams marketed in Mangalore, India. According to the authors, STEC is prevalent in seafoods in India, and non-O157 serotype is more common. In Brazil,(Ayulo et al., 1994) isolated only one strain of STEC from shellfish, and evidence that preventive measures especially during harvest and post-harvest are of major importance to avoid contamination of any nature. For (Feldhusen, 2000), when present in marine seafood or fresh cultured products, pathogenic bacteria levels are considerably moderate. Seafood, although an important element of Mediterranean diets, plays a significant role in causing food borne diseases.

Fresh seafood is a highly perishable product and spoilage developing in aerobically stored fish typically consists of Gram-negative psychrophilic non-fermenting rods. Thus, under aerobic ice storage, the flora is composed almost exclusively of Pseudomonas spp. and Salmonella putrefaciens (Chouliara et al., 2004). The Enterobacteriaceae count is considered as another index of fish quality because it is related to storage in ice, washing and evisceration (Zambuchini et al., 2008). A monitoring of these microorganisms has been suggested as a measure of fish quality. Also, risk management decisions should take into account the whole food chain from primary production to consumption, and should be implemented in the context of appropriate food safety infrastructures, for instance regulatory enforcement, food product tracing and traceability systems. In the fish processing chain managing risks should be based on scientific knowledge of the microbiological hazards and the understanding of the primary production, processing and manufacturing technologies and handling during food preparation, storage and transport, retail and catering (Reilly, 2006). Seafood products harvested from contaminated waters or which have been improperly preserved after harvesting are known to play an important role in infections by Vibrio spp.

1.2       AIMS AND OBJECTIVES

1.         To determine the microbial load of frozen fishes

2.         To identify possible pathogens from the frozen fish.

3.         To determine the antibiotics susceptibility pattern of the isolate.

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