CHAPTER ONE

INTRODUCTION

1.1 Background to the Study

 Fish is a very vital source of high quality protein and constitutes an important part of man’s diet; it is one of the most important animal foods available in the tropics (Eyo, 2001). Catfish, (Clarias gariepinus) accounts for about 80% of aquaculture production in Nigeria (FDF, 2003).

However, fish is a perishable food material that deteriorates soon after harvest at high ambient temperature (Aberoumand, 2010); therefore, needs immediate preservation. Fish products are among the most perishable commodities worldwide mainly due to microbial spoilage. About one-third of the world’s food production is lost annually as a result of microbial spoilage (Omojowo et al., 2010).

 

Microorganisms inhabit nearly every niche of the earth and our food is no exception (Pelczar et al, 1993). Also, microorganisms in food may also be responsible for food poisoning and food-borne infections (Ogwan’g et al., 2005). Immediately fish dies, it remains in first class quality only for a short while (Eyo, 1997; 2001; Abolagba and Melle, 2008). Thus, the quality of fish as well as its potential keeping time deteriorates rapidly leading to food loss with regards to acceptable quality.

 

Furthermore, a number of processing techniques are in operation in Nigeria. These include chilling, freezing, salting, canning, drying and smoking. However, smoking is the most popular method of fish processing (Eyo, 2000) who reported that: smoking involves heat application to remove water and inhibit bacterial and enzymatic action on fish. Traditional methods are being used for the preservation of fish especially in rural areas (Chakrabarti and Varma, 1999). It imparts aroma, taste and colour on processed fish (Olley et al., 1988). Meanwhile, smoking of fish from smouldering wood for its preservation dates back to civilization (Olokor, 2007). It is also noted that apart from giving the product a desirable taste and odour, smoking provides a longer shelf life through its anti-bacterial and oxidative effect, lowering of pH, imparting desirable colouration as well as accelerating the drying process and acting  thus create public awareness on the health implications of their consumption.

 

Sengor et al., 2004). However, the effect of curing by smoking with respect to quality and shelf life of the product depends on the preparation of the raw material, the type of smoking, relative humidity, velocity, temperature, density, and composition of the smoke, and the time of smoking (Doe, 1998). To satisfy the consumer demand, it is necessary to produce good quality and safe smoked seafood products (Omojowo et al., 2010).

 

Microbial activity is responsible for spoilage of most fresh and of several lightly preserved sea foods (Lund et al., 2000). Smoked fish and shellfish products can be a source of microbial hazards including Listeria monocytogenes, Salmonella spp.,and Clostridium botulinum (Heintz and Johnson, 1998). Also, Abolagba et. al. (2011) and Abolagba and Uwagbai (2011) stated that bacteria such as Staphylococcus aureus, Proteus, Bacillus, Micrococcus, were the most common microorganism associated with smoked fish. Customers mostly assess the quality of fish by considering the appearance, smell and palatability of the fish when cooked

hence it is necessary to produce good quality and safe smoked fish free from harmful microbial load (Abidemi-Iromini et al., 2011). In hot smoking process, the fish is properly cooked with the temperature reaching 120˚C while the centre of the fish flesh may reach 60˚C.

Hot smoking is the tradition method of fish smoking in the tropics. Fish is smoked until cooked in order to obtain a product with extended shelf life, since alternative preservation method such as refrigeration are absent in remote fishing villages where most fish processing takes place.

 

The primary aim of hot smoking is to preserve the product, flavour and colour arising as a result of preservation function. This study is aimed at understanding the safety or harm of smoked catfish products after smoking process. It is to identify microorganisms that contaminate the catfish.

 

1.2 Statement of the Problem

 

The challenge in facing fish production in Nigeria is the unhygienic environmental conditions in which fish finds itself after capture, before it comes to the table for consumption (Akrofi, 2002). In addition, poor hygiene practices are likely to contribute to contaminating fish with microbes. Of much concern to public health, safety and the environment is the contamination of fish with pathogens (Farmer et al., 2003; Su and Liu, 2007). In Nigeria and other parts of the world, consumption of fish contaminated with pathogens has raised major health concerns and are responsible for some of the reported deaths (Mensah et al., 2002; WHO, 2002; Scott et al., 2007). Colakoglu et al. (2006) reported that the characteristics of fish make it a suitable living and proliferation medium for bacteria. The presence of pathogens such as Vibrio spp. and

1. coli in fish has raised major concerns among scientists as constitute the main causes of food-borne illnesses (WHO, 2007). Most people also believed that smoked fish is very safe and can be eaten without further heat processing. It is therefore not uncommon to find people eating fish in the market before any post-smoking heating is done.

 

 

Ukpebor et al. (2005) observed that heavy metal are non-biodegradable and undergo a global eco-biological cycle in which natural waters are the main pathways. Fishes may absorb dissolved elements and trace metals from the food chain and surrounding water and accumulate these metals in their flesh at concentrations greater than the ambient water and pose a major health threat to consumers. Ademoroti (1996) reported that heavy metal in the human body can attack proteins particularly enzymes in the human body, Ukpebor et al. (2005) also concluded that the toxic effects of heavy metal are cumulative

and cause gradual poisoning of the human system over a period of time. Heavy metals have been associated with the upsurge of liver and kidney diseases, and are believed to be responsible for a higher percentage of mortality caused by kidney and liver morbidity (Ndiokwere, 2004). Other implications include memory loss (Grandjean et al., 1994), neurological damage and immune system suppression which can cause foetal abnormalities in mammals (Guallar et al., 2002; Clarkson et al., 2003). The health risks associated with heavy metal poisoning in man and the environment are of great concern to environmentalists and government agencies and underlines the need for continuous study.

 

 

The current study was aimed at understanding the microbiological contamination of tuna fish species [Katsuwonus pelamis (Skipjack) and Thunnus albacares (Yellowfin)] at landing, after smoking and in the retail market (smoked) from different landing beaches in the Greater Accra Region of Nigeria. It determined the microbial contaminations along the traditional fish processing chain. The study also considered selected heavy metal (Hg, Pb, and Cd) contaminations of these fish species to see if the fish caught in Nigeria waters meet the requirements of local consumption as well as exports. In this study, two main species of tuna (K. pelamis and T. albacares) landed in Nigeria were considered because they are the most preferred species and smoking was the preferred processing method for this study because it is the commonest form in which fish is processed in Nigeria (Adu- Gyamfi, 2006).

 

1.3  Objective of the study

The main objective of this study is on Microbial Assessment Of Smoke Catfish Sold In Ngomari Constrain Bus Stop

Specific objectives

 

The specific objectives of the study were to determine the:

 

1. Microbiological contamination of cat fish before smoking
2. Effect of smoking on the microbiological contamination of catfish in the  traditional fish smoking chain in Ngomari Constrain Bus Stop
3. Levels of selected heavy metal (Hg, Pb and Cd) concentration in catfish

 

 

 

 

1.4 Scope of the Study

This work is concentrated on the Microbial Assessment Of Smoke Catfish Sold In Ngomari Constrain Bus Stop. The reason for the study area is because of its proximity to gather data needed for the study by the researcher.

 

1.5 Significance of the Study

It is envisaged in this study that fish processors be advised to choose high quality fish products. This is because, people eat smoked fish due to the flavour and texture that the fish acquires on smoking and they deserve to eat products of high quality. Also it is noted that the contamination of the fish samples is as a result of post-processing handling of smoked catfish products which is not properly done.

The smoked catfish is observed to be displayed on newspaper on a flat basket and opened for flies to perch on. The houseflies contaminate them with dirt from the surrounding environment. Some of these smoked fish products are prepared or processed poorly that if they do not reach the markets the same day, they get spoilt and cause loss to the fish processor.

The findings of the study should be used to enlighten the fish traders and consumers of the inherent harm and design steps necessary in lengthening shelf life of smoked catfish products.

1.6 Limitations of the Study

Financial Constraints: The researcher was with limited funds, she cannot visit all the areas to get responses from respondents but she was able to get good information concerning the research topic.

Time Constraints: The researcher was involved in other departmental activities like seminars, attendance of lectures et.c which limited her time for the research but the researcher was able to meet up with the time assigned for the completion of the research work.

 

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