ABSTRACT
The aim of this study was to evaluate the nutritional composition, bacterial load and organoleptic quality of farm-raised African catfish (Clarias gariepinus; Burchell, 1822) in the Dormaa Municipality. Thirty (30) specimen of freshly harvested fish Clarias gariepinus of average weight 912.78 ± 16.43 g obtained from a fish farm and an equal number of smoked farm-raised fish of average weight 769.19 ± 6.48 g were used for the study. Proximate analysis, bacterial and organoleptic quality assessments yielded the following results: The mean percent moisture, ash, fat, protein and total carbohydrate contents for fresh farmed fish were 77.4 ± 1.94%, 1.34 ± 0.26%, 0.57 ± 0.17%, 17.58±0.23% and 4.45 ± 1.55% respectively. The corresponding levels in smoked farm-raised fish were 11.63 ± 0.43%, 7.06 ± 0.66%, 9.31 ± 1.80%, 25.72 ± 1.51% and 53.34 ± 0.15% respectively. The mean total viable counts, total coliform counts, Staphylococcus aureus and E. coli for the fresh fish were respectively 2.2×105 cfu/g, 8.7×102 cfu/g, 5.5×103 cfu/g and 2.3×103 cfu/g. For the smoked fish, mean total viable counts, total coliform counts, S. aureus and E. coli were 4.2×105 cfu/g, 0.0 cfu/g, 2.8×103 cfu/g and 2.5×103 cfu/g respectively. The overall acceptability of fresh and smoked farm-raised catfish ranged from 3.2 to 4.6 and 3.0 to 3.8 respectively. There were significant differences (P < 0.05) in the nutritional, bacterial and organoleptic qualities between the fresh and smoked catfish. Results from the study revealed higher nutritional composition in smoked catfish and lower bacterial loads in both fresh and smoked fish except E. coli, which must be of concern for consumer safety.
TABLE OF CONTENTS
Contents Page
DECLARATION……………………………………………………………………………………………………………………………….. II
ABSTRACT………………………………………………………………………………………………………………………………………. III
DEDICATION…………………………………………………………………………………………………………………………………… IV
ACKNOWLEDGEMENTS…………………………………………………………………………………………………………… V
LIST OF FIGURES………………………………………………………………………………………………………………………… IX
LIST OF TABLES……………………………………………………………………………………………………………………………. X
LIST OF APPENDICES………………………………………………………………………………………………………………. XI
CHAPTER ONE…………………………………………………………………………………………………………………………………. 1
INTRODUCTION………………………………………………………………………………………………………………………………. 1
1.1 BACKGROUND…………………………………………………………………………………………………………………………………. 1
1.2 JUSTIFICATION…………………………………………………………………………………………………………………………………. 4
1.3 OBJECTIVE OF THE STUDY…………………………………………………………………………………………………………….. 6
CHAPTER TWO………………………………………………………………………………………………………………………………… 7
LITERATURE REVIEW…………………………………………………………………………………………………………………. 7
2.1 FISHERIES IN GHANA……………………………………………………………………………………………………………………… 7
2.2 AQUACULTURE PRODUCTION IN GHANA……………………………………………………………………………………. 7
2.3 MERISTIC AND BIOLOGICAL FEATURES OF CLARIAS GARIEPINUS………………………………………….. 8
2.4 REPRODUCTION OF CLARIAS GARIEPINUS………………………………………………………………………………… 9
2.5 FOOD AND FEEDING HABITS OF CLARIAS GARIEPINUS…………………………………………………………….. 9
2.6 GLOBAL CAPTURE PRODUCTION OF CLARIAS GARIEPINUS………………………………………………….. 11
2.7 NUTRITIONAL QUALITY OF CLARIAS GARIEPINUS……………………………………………………………………. 11
2.8 MICROBIAL QUALITY OF CLARIAS GARIEPINUS……………………………………………………………………….. 14
2.9 ORGANOLEPTIC ATTRIBUTES OF FARMED CLARIAS GARIEPINUS………………………………………… 16
CHAPTER THREE………………………………………………………………………………………………………………………… 20
MATERIALS AND METHODS…………………………………………………………………………………………………. 20
3.1 STUDY AREA………………………………………………………………………………………………………………………………….. 20
3.2 FIELD PROCEDURES……………………………………………………………………………………………………………………. 22
3.2.1 Samples of fresh fish……………………………………………………………………………………………… 22
3.2.2 Smoked fish samples…………………………………………………………………………………………….. 22
3.3 PROXIMATE ANALYSIS OF FISH……………………………………………………………………………………………………. 22
3.3.1 Moisture Content……………………………………………………………………………………………………… 23
3.3.2 Crude protein……………………………………………………………………………………………………………… 23
3.3.3 Ash content…………………………………………………………………………………………………………………. 24
3.3.4 Fat content…………………………………………………………………………………………………………………… 24
3.3.5 Total carbohydrate………………………………………………………………………………………………….. 24
3.4 MICROBIOLOGICAL ANALYSIS OF FISH………………………………………………………………………………………. 24
3.4.1 Enumeration of Total Viable Aerobic Count…………………………………………….. 24
3.4.2 Total coliform count……………………………………………………………………………………………….. 25
3.4.3 Staphylococcus aureus……………………………………………………………………………………….. 25
3.4.4 Escherichia coli…………………………………………………………………………………………………………. 25
3.5 ORGANOLEPTIC ASSESSMENT OF FISH……………………………………………………………………………………… 26
3.6 STATISTICAL ANALYSIS………………………………………………………………………………………………………………… 26
CHAPTER FOUR…………………………………………………………………………………………………………………………… 27
RESULTS…………………………………………………………………………………………………………………………………………… 27
4.1 NUTRITIONAL COMPOSITION……………………………………………………………………………………………………….. 27
4.2 MICROBIOLOGICAL ANALYSIS……………………………………………………………………………………………………… 28
4.3 ORGANOLEPTIC PROPERTIES……………………………………………………………………………………………………… 29
CHAPTER FIVE………………………………………………………………………………………………………………………………. 33
DISCUSSION……………………………………………………………………………………………………………………………………. 33
5.1 NUTRITIONAL COMPOSITION……………………………………………………………………………………………………….. 33
5.2 MICROBIOLOGICAL QUALITY……………………………………………………………………………………………………….. 35
5.3 ORGANOLEPTIC QUALITY…………………………………………………………………………………………………………….. 37
CHAPTER SIX…………………………………………………………………………………………………………………………………. 39
CONCLUSIONS AND RECOMMENDATIONS……………………………………………………………….. 39
6.1 CONCLUSIONS………………………………………………………………………………………………………………………………. 39
6.2 RECOMMENDATIONS……………………………………………………………………………………………………………………. 39
REFERENCES………………………………………………………………………………………………………………………………… 41
APPENDICES………………………………………………………………………………………………………………………………….. 54
LIST OF FIGURES
Figure Page
Figure 1: A map of Ghana showing the Dormaa Municipal Area.……………………… 21
Figure 2: Nutritional composition of fresh and farm-raised catfish from the Dormaa
Municipality.……………………………………………………………………………………………………………………….. 28
Figure 3: Organoleptic properties of fresh farm-raised catfish.…………………………. 3
Figure 4: Organoleptic properties of smoked farm-raised catfish.…………………..
LIST OF TABLES
Table Page
Table 1: Microbial content of assessed smoked and fresh catfish from the
Dormaa Municipality……………………………………………………………………………………………………… 29
Table 2: Organoleptic attributes of fresh and smoked farm-raised catfish... 32
LIST OF APPENDICES
Appendix Page
Appendix 1: A five-point Hedonic scale for organoleptic studies……………………. 54
Appendix 2: Sample T-test for biochemical composition of fresh and smoked
farmed catfish. 55
Appendix 3: Sample T-test for microbiology characteristics of fresh and smoked
farmed catfish. 60
Appendix 4: Sample T-test for sensory characteristics of fresh and smoked farmed
catfish.……………………………………………………………………………………………………………………………
64
CHAPTER ONE
INTRODUCTION
1.1 BACKGROUND
In Ghana, fish is considered the prime source of animal protein alluding to its relatively large scale of production and consumption in comparison with other protein source alternatives such as meat. The African Catfish in Ghana, otherwise known as (Clarias gariepinus, Burchell, 1822), is an extremely vital freshwater fish and hence being the second most cultured freshwater fish in the country (FAO, 2016). Due to its distinctive taste, texture and flavour, it has largely been accepted in most parts of Ghana. An evidence of their wide acceptability has being shown in their extensive distribution and cultivation in most ponds nationwide. Being a major source of vitamins, proteins and minerals, fishes contain other important nutrients required to complement diets of both adults and infants (Abolagba et al., 2015; Alao et al., 2017).
Fishes, as observed in most African countries, are consumed fresh, preserved or processed dried or smoked in most cases and is considered by most as a much-appreciated delicacy irrespective of financial, religious, age and educational boundaries (Adebayo-Tayo et al., 2008). African catfish is amongst the fish species of utmost significance, presently being cultured in and out of its natural range with regards to geographical location tropical and
subtropical (Adewolu et al., 2008). Ghana places second to Nigeria in the West African sub-region in terms of production and consumption of this species of fish (FAO, 2016). Its possession of certain unique characteristics, some of which include high rates of fertility, easy production of larvae during captivity and high resistance with regards to diseases make it commercially viable in aquaculture (Haylor, 1991). It is of incredible significance since it develops rapidly, accomplishes a table size in a short time and is a consumable fish with limited flesh spines. It can endure an extensive variety of ecological conditions, as well as extreme temperatures, and low levels of oxygen. The significance of catfish to human diet can therefore not be exaggerated. As indicated by Anoop et al. (2009), it gives sustenance to the people, it permits enhanced protein nourishment since it contains a high biological value with regards to high protein retention in the body, higher protein absorption in comparison to alternative sources of protein, small cholesterol substance and a prime animal protein source when considering safety.
Research has shown that for newly harvested fish, the microbial flora accompanying it is essentially as a result of the surroundings within which the fish is harvested and not the type of fish; subsequently, the local microbial populaces of fish can differ considerably (Shewan, 1961). It further stated that owing largely to their delicate tissues and aquatic surroundings, fishes are particularly vulnerable to microbial pollution. Masses of bacteria, a considerable lot of them potential spoilers, are Despite the possession of typically sterile flesh, bacteria are available in the surface sludge, on the gills and in the digestive tracts of live fish. When alive, the natural defence barrier of fish stalls or inhibits the development and intrusion of bacteria yet after death the guard framework breaks down and the
microscopic organisms increase and attack the flesh (Abolagba and Uwagbai, 2011). Large amounts of fish spoilage have therefore been attributed to inappropriate postharvest technology, which includes handling, preservation and processing, all of which has the potential of negatively impacting fish wholesomeness unhealthy situation. In Nigeria, total fish landings have been associated with an approximation of 40% postharvest losses (Akande, 1996).
Consequently, it is essential to process and reserve a portion of the fish harvested in the time of plenty, in order to guarantee supply throughout the year. Processing and preservation will subsequently lessen losses incurred after harvesting, prolong fishes’ shelf-life while ensuring a viable supply of fish all year round. In Ghana, a host of processing techniques aimed at ensuring the reasons named above, are in operation. Smoking is, however, the most prominent and probably the least difficult fish processing technique amongst a host of others as it does not necessitate complex tools or exceedingly resourced workers (Olayemi et al., 2011).
In many third world countries, the oldest and most popular conservation technique is smoking (Kumolu-Johnson et al., 2010). It is a conservation technique that incorporates the burning of wood which subsequently produces natural chemicals through a combination of drying and decomposition (Tobor, 2004). Through the process of wood burning (incomplete), smoke is produced which in turn gives fishes a unique colour and flavour.
Smoke contributes to fish preservation and shelf life by drying, cooking, acting as an effective antioxidant, bacteriostatic and bactericidal agent as well as by depositing natural wood–smoke chemicals like tars, phenols and aldehydes; all of which provide a protective film on the surface of smoked fish and have powerful bactericidal action and prevent the growth of other microorganisms on the flesh of the fish (Swastawati et al, 2000; Daramola et al., 2013). A host of techniques are accessible for smoking fish and varied smoked items have been produced in different areas of the globe in connection to the properties of the locally existing raw materials and the overall level of expertise (Olley et al., 1988). The most suitable smoke condensate for the elaboration of particular fish could be used to evaluate sensory value, as well as microbiological, chemical and safety point of view. In relation to consumer preferences, it is indicated that consumers do not like the same kind of products. For example, some people require a strong smoke odour and flavour, others want a specific “wood or smoke material (Cardinal et al., 2006).
1.2 JUSTIFICATION
Consumers in recent times, have begun to comprehend that their choice of food can have a subsequent impact on their health (Franz and Nowak, 2010). A healthy diet has now become a trending topic attracting vast global consideration (Kaimakoudi et al., 2013). Research indicates that modern consumers of varied age groups are well informed of the nutritional and health benefits derived from fish consumption (He, 2009). As a result of the nutritional value of fish, such as omega-3 fatty acids, vitamins and minerals coupled with its ease of digestion, fish consumption by all irrespective of age is encouraged. Owing to the consistent increment in the human populace and nutritional benefits of fish
consumption, the demand for fish has been on the rise (Claret et al., 2014). This increase in the demand for fish has resulted in diminishing resource base of capture fisheries, owing largely to unsustainable fishing methods being employed which is adversely causing a reduction in wild fisheries contribution to fish food security (FAO, 2004). In an effort to address decreasing wild fish stock and an upsurge in the demand for fish by consumers, they are being given the viable option of farmed fish (Cahu et al., 2004).
Catfish (particularly fresh wild catfish) has become an increasingly popular foodstuff in the Brong Ahafo region of Ghana, with significant production centred in five major districts including Dormaa Municipality, however, farmed catfish production in the municipal suffers post-harvest losses especially to small-scale fish farmers who are in the municipality. This is due to the plethora of factors including the presence of microorganisms, unhygienic handling of farmed fish as well as the absence of a ready market.
The presence of micro-organisms such as bacteria impairs the nutritional quality of fish and its organoleptic attributes. It is therefore important to establish baseline data on nutritional composition and also investigate the microbial load and organoleptic quality of farmed catfish both smoked and fresh. This could help educate small-scale farmers on good handling practices that would make their produce acceptable on the market.
1.3 OBJECTIVE OF THE STUDY
The study aimed at understanding the nutritional, bacterial and organoleptic quality of farm-raised African catfish, Clarias gariepinus in the Dormaa Municipality of the Brong Ahafo Region in Ghana.
The specific objectives were to:
Determine the proximate composition of fresh and smoked farm-raised African catfish;
Investigate the bacterial load of the fresh and smoked African catfish;
Evaluate the organoleptic quality of the processed and unprocessed fish.
