Bacteriological Quality Of Smoked Fish Would Cover The Bacteria That Affect Smoked Fish And Its Public Health Implications

Project and Seminar Material for Microbiology

Project and Seminar Material for Microbiology


Fish are classified as any of the cold-blooded aquatic vertebrates of the super class Pisces typically showing gills, fins and streamline body. In addition Fish also refers to any other form of marine or fresh water animal that can be used for human consumption. Fish is also an important part of a healthy diet since it contains high quality protein but typically presents a low fat percent when compared to other meat.Microbial assessment of smoked Scombia scombia spp. of fish procured from the market and fish factory in Owerri metropolis was carried out.

The samples were analyzed using bacteriological and fungi media. As one of the common sources of protein available to man, fish is highly consumed due to its lower cholesterol content and price. So, it forms a rich protein source for both poor and rich. As a part of checkmating the public health risks associated with this general dependence of the population on fish, the microbiological assessment of smoked fish, Scombia, scombia sold in Owerri was embarked on with the aim of ascertaining the microbial quality, the presence and prevalence of microorganisms of public health importance.

A total of one hundred and eight (108) samples were collected from the smoking Factory, Open Market and Hawkers. These were analyzed microbiologically for viable heterotrophic bacteria and fungi count on Nutrient and Potato dextrose agar respectively, using pour plate method and coliform count in MacConkey broth by multiple tube method (MPN). The mean value results from the analysis revealed high microbial contamination in all the samples. The resultant data were analyzed statistically using randomized block design of Analysis of Variance (ANOVA) at 95% level of confidence and the difference were separated using the least significance difference (LSD).

The mean results of viable heterotrophic bacteria and fungi count showed no significance difference for the collection sites; but the coliform mean results for the three sites showed marked variation at 95% level (P>0.05). Identified bacteria, include: Staphylococcus aureus, E. coli, Bacillus sp., Klebsiella sp., whereas fungi are Penicillium sp., Aspergilusl sp., Fusarium violaceum, Biospora sp., Candida sp, Botryodioplodia sp., Alternania sp. This high level of microbial contamination can be traceable to handlers, and environment to which this fish is exposed during smoking and selling exercises, and considering the danger it portends to human health, public health and food safety authorities should intensify their monitoring efforts towards controlling such contamination.

Table Of Contents

Preliminary Page(s)

  • Title
  • Declaration
  • Approval
  • Dedication
  • Acknowledgement
  • Abstract
  • Table of Content

Chapter One:


  • 1.1 Background of the study
  • 1.2 Statement of the problem
  • 1.3 Objectives of the study
  • 1.4 Significance/ Justification of study
  • 1.5 Scope of the study

Chapter Two:

Literature Review

  • 2.1 Fish Demand and Supply in Nigeria
  • 2.2 The Fish Value Chain in Nigeria
  • 2.3 Fishborne Diseases
  • 2.4 Staphylococcus aureus
  • 2.5 Methicillin Resistance
  • 2.6 The Genus Salmonella

Chapter Three:

Materials And Methods

  • 3.1 Sample collection
  • 3.2 Sample preparation and Laboratory analysis
  • 3.3 Pour Plate Method
  • 3.4 Most Probable Number (MPN) Method
  • 3.5 Statistical analysis

Chapter Four:

Result And Discussion

  • 4.1 Result
  • 4.2 Discussion

Chapter Five:

Conclusion And Recommendations

  • 5.1 Conclusion
  • 5.2 Recommendations
  • References

Chapter One


1.1 Background of the study

Fish is a vertebrate animal, living in fresh and seawater. It is one of the main sources of animal protein foods available for human consumption. Most of the catch comes from oceans, seas, rivers and lately from man-made ponds. It is a highly nutritious food of about 60-80% water, 15-25% protein, 11-22% fat, 20% mineral and 1% carbohydrate. It is often cheaper than meat and so it is a rich protein source for both the poor and the wealthy.
In Nigeria, fish and fish products constitute more than 60% of the total protein intake in adults, especially in the rural areas, and they supply a good balance of protein, vitamins and minerals. Fish has a caloric content of relatively 10%, which enhances its value, as well as its role in the nation’s nutrition (Akinneye et al., 2007).

Microbial flora of fish depends on the microbial content of the water in which they live as the slime that covers the surface of fish has been found to contain great variety of bacteria general. Many dangers therefore exist if fish harvested from polluted water is eaten raw, and because of the high bacteriological quality of freshly harvested fish it is susceptible to rapid spoilage. Hence preservation of fresh fish becomes very important. This can be achieved by freezing, drying through smoking and sun-drying, canning, etc.

Smoking simply means a heating process that dries the fish to preserve it from spoilage. Most dry fish consumed in Nigeria are smoked. Smoking of fish from smoldering wood for its preservation dates back to civilization. The steps in the smoking process are necessary not only for safe preservation, but also to produce good flavor and aroma. Hence, smoked fishes are less prone to microbial spoilage than fresh fish. However spoilage still occurs as a result of growth of microbes due to partial dehydration during smoking.

Consumption of fish and fish products is recommended due to good digestibility and the high content of polyunsaturated fatty acids. Fishes are a rich source of protein commonly consumed as an alternative source of protein due to the higher cost of meat and other sources of animal protein (Oluwaniyi and Dosumu, 2009). Fish has lower cholesterol content when compared with meat and thus often recommended for consumption especially among the adult population (Harris, 1997). The marine fish is generally cheaper and more abundant when compared with fresh water fishes, which are relatively more expensive in Nigeria (Oluwaniyi and Dosumu, 2009). Fish is a highly perishable food and so, many strategies have been developed to limit its spoilage (Gómez-Estaca et al., 2009).

According to KumoluJohnson et al. (2010) various food preservation techniques have been utilized to improve the microbial safety and extend the shelf-life of fish in general including freezing, chemical preservation, salting, smoking, frying and filleting. However, smoking is the most popular method of fish processing (Bako, 2004). Food is considered to be microbiologically unsafe owing to the presence of microorganisms which may invade human body (e.g Salmonella, Escherichia coli, Listeria monocytogenes, etc) and also those that produce toxins ingested with a food such as Staphylococcus aureus, Clostridium botulinum and Bacilus cereus (Ofred, 2009). The growth of these pathogens may not necessarily results in food spoilage. Hence the absence of deleterious sensory changes cannot be used as an indicator for food microbiological safety (Border and Norton, 1997). Consequently many outbreaks are caused by bacteria originating in the animal/human reservoir including Salmonella, Shigella, E. coli, and Staphylococcus aureus, (Huss et al., 1997). Generally fish and shellfish are common vehicles of transmitting food borne diseases.

Contamination of fish and other fishery products by microbes has been a serious threat to human health. There are four main factors responsible for fish spoilage once it is out of its natural habitat (water) and these include: Autolysis which usually precedes bacterial spoilage and involves the breakdown of protein and lipids to amino acids and fats by muscle enzymes. The activity of microorganism is another factor which uses the amino acid produced by autolysis for proliferation. Others are chemical deterioration and insect attack which cause considerable deterioration.

However, spoilage of fresh and highly preserved fish products is mostly caused by microbial action. Foods of high sugar/salt contents are therefore most likely to be spoiled by any kind of microbe. It has been reported that serious disease outbreak had occurred in both man and animals after consuming some dried fish feed and food. This could be as a result of disease causing microorganism like Escherichia coli, Salmonella typhi, Vibrio cholera which results from poor handling/cross-contamination and improper processing practice of ready to eat “smoked fish” products. Other microorganisms of primary concern are Listeria monocytogen and Clostridium botulinium. Extensive handling provide opportunities for other food borne pathogens to contaminate products if sufficient attention is not given during smoking process.

This work therefore tends to investigate the level of sanitation maintained by handlers during processing and storage of smoked fish sold in Owerri.

1.2 Statement of the problem

The problem of fish in Nigeria however, is its high rate of perishability especially since the relative ease of preservation is not readily attainable, hence the difficulty in handling. Generally, the different preservation methods are: drying, smoking, freezing, chilling and brining but the common method in Nigeria is smoking (Akinola et al., 2006).

Smoking (the commonly adopted method of preserving fish in Nigeria), as an international source of foreign exchange is gradually losing ground (Al – Jafali and Opara, 2006); this is because exportation of smoked fish to developed countries is becoming increasingly stringent due to the emergence of food safety and agricultural health standard, along with the fact that buyers keep changing their requirements. The quality of processed food usually depends on the processing and handling techniques employed (Al-Jafaili and Opara, 2006). This is particularly true of smoked fish in view of the presence of endogenous organisms. Food poisoning organisms can multiply profusely in foods without initially altering the appearance, taste or odour.

A large number of people suffer from gastro-intestinal upsets annually, as a result of eating contaminated food which leads to a considerable loss of man-hour with accompanying consequences. Sometimes death occurs.
In many instances, outbreaks result from lack of understanding of food hygiene in the preparation, cooking and care of food. In order to avert such outbreaks, safety evaluation is necessary. Determination of pathogenic loads, by microbial tests for ascertaining risk level as well as potential sources in the smoked fish could be part of the palliatives.

1.3 Objectives of the study

The main objective of the study is to determine the bacteriological quality on smoked fish sold in Owerri.
Specifically, the study tends to;

  1. Assess the food safety knowledge, attitude and practices of smoke fish handlers along the fish value chains.
  2. Examine the microbial quality in smoked fish.
  3. Assess the presence and prevalence of microorganisms of public health importance

1.4 Significance/ Justification of study

Fish is one of the cheapest sources of animal protein in Nigeria and its production has the potential to make substantial contributions towards addressing the food and nutrition security challenges of the country (Amiengheme, 2005). In order to realize this potential, however, it is essential to understand the public health threats associated with the development and expansion of the fish value chains in Nigeria. Currently, ongoing research on animal sourced food value chains seemed to have focused mainly on high turnover livestock sectors, particular poultry and dairy industry, with little attention being paid to the fish sector. As such, one of the justifications for this research project was to generate information that would guide public health policy development for the Nigerian fish industry.

With tremendous increase in consumption of fish, there have been only a limited number of studies conducted which focused on hygiene and safety of both domestic fish and frozen fish value chains. The results of the studies therefore addressed the shortfalls in information regarding the food safety and hygiene measures of stakeholders in fish value chains in Owerri metropolises.

The study was designed to provide useful potential risks associated with consumption of fish, it‘s processing and handling practices through evaluation of the microbial burden. The level of microbial contaminants along fish value chains will provide baseline information for policy development on the hazard analysis and critical control points (HACCP). Cultural, biochemical and molecular evaluation will emphasize the presence of these organisms and biochemical characteristics such as the burden, pathogenic strains, and resistance profile. Antimicrobial resistance profile of circulating strains of S. aureus and Salmonella spp. could help clinicians in selecting the efficient antibiotics in cases of infections. The basic phenotypic characteristics of these agents to antibiotics will help in development of meaningful strategy for disease surveillance and control programme.

1.5 Scope of the study

The study was limited to smoked Scombia, scombia sold in Owerri.

Chapter Five

Conclusion And Recommendations

5.1 Conclusion

The study showed that though smoking helps in inhibiting the activities of microorganisms, however, when not properly carried out, microbial growth and activities still continue, leading to the deterioration of the fish.
The result of this work has proven that smoked fish sold in Owerri are contaminated right from the factory point. This implies that smoking is not an effective means of preservation and prevention of microbial proliferation in fish. This work also has shown that bacteria and fungi are responsible for the microbial contamination of smoked fish.

5.2 Recommendations

Based on these findings, we are recommending the use of mechanized smoking system that would completely dehydrate the fish in order to prevent contamination due to moisture. Also we are recommending that regulatory authority such as NAFDAC should look into the environmental condition of our food handlers as it concerns the smoking factories, the markets where our foods are sold and even the hawkers that carry the food from one place to another. Their hygienic condition must be ascertained before authorizing them to handle public food.

Finally, we are recommending that people should properly cook their fish before eating even when it is smoked to avert food poisoning.

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