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FST00094 - THE FATTY ACID AND PROXIMATE COMPOSITION OF CATFISH


 

CHAPTER ONE

1.0       INTRODUCTION

            The importance of fish to man cannot be overemphasis in the world today. The major importance of fish to human is majorly to serve as a source of protein, and they are being converted to different forms for different purpose. The African catfish, Clarias gariepinus has been reared for about 20 years in Africa with mixed success; the total farmed production of this species being only 3,978 metric tones or 7.4% of the of the total farmed fish production of 69,434mt in Africa in 1994 (Balogun, 2000). The nutritional benefits attributed to fish are particularly obtained from its exceptionally advantageous fatty acid profile. In recent years, increasing attention has been focused on the significance of polyunsaturated fatty acids in human nutrition, particularly eicosapentanoic acid (EPA) and docosahexaenoic acid (DHA) that are practically only found in fish. This increased attention is as a result of their positive effect in ameliorating some disease conditions, cardiovascular diseases high up on that list (Kris- Etherton et al., 2002).

The -3 polyunsaturated fatty acids (PUFAs) also play a vital role in the development and function of the nervous system (brain) and the reproductive system (SanGiovanni and Chew,

2005; Bourre, 2007). Eicosapentaenoic acid and docosahexaenoicacid, along with other

monounsaturated and polyunsaturated fatty acids have demonstrated benefits in the prevention and treatment of cardiovascular diseases (CVDs) (Kris-Etherton et al., 2002; Mattson and Grundy, 1985), stroke, lupus nephropathy, hypertension, rheumatoid arthritis, breast cancer, colon cancer, prostate cancer (Levine and Barbara, 1997; Woods, 2008), autoimmune diseases, preventing weight loss in cancer patients (Uauy-Dagach and Valenzuela, 2000), eye sight and the improvement of learning ability (Nielsen et al., 2005).EPA and DHA are particularly proven as the precursors of composite hormones known as eicosanoids, which are involved in several metabolic processes of the human body (Harris, 2004; Inhamuns and Franco, 2008). Generally, when lipids are stored mostly in the liver, with little or nothing being stored in the

muscles of the fish, they are termed as lean fish. If the excess stored in the muscles are much, they are termed as fatty fish (Sutharshiny and Sivashanthini, 2011). Based on fat content of the

muscles, fish could be either lean fish (<5% fat by weight), medium-fat (5-10% fat by weight) and high-fat fish (>10% fat by weight) (Gurr, 1992).

Fish farming, or aquaculture, has been the fastest growing sector of animal food production in the world since 1970. Due to a decline in wild fish populations and a growing human population,

aquaculture is expected to fill the gap in supplies of fish as food for humans, as demand continues to increase (FAO, 2008). The fatty acid profile of fish vary with species and

could be affected by many factors such as temperature, salinity, season, size, age, species

habitat, life stage, and the type and abundance of food, especially whether a species is carnivorous, herbivorous or omnivorous (Ackman, 1989; Saito et al., 1999; Sargent et al., 1999). As the world's fish stocks are getting limited, cultured fish is now being proposed as an alternative for consumption. Clarias gariepinus, or the African sharp-tooth catfish

is a species of the family Clariidae, the airbreathing catfishes. The African catfish is cultured

mainly in Africa and Europe (Hecht et al., 1985) although it is now also receiving attention in India, China and some East European countries (Huisman and Ritcher, 1987). It however has

grown in importance in Nigeria over the years (Idodo-Umeh, 2003). The African catfish is

considered to be one of the most important tropical catfish species for aquaculture because of

a number of characteristics/factors, among which are its good meat quality, ability to tolerate adverse environmental conditions far better than other fishes do and its high growth rate even at high stocking densities. These factors contribute to its geometric rise in preference for commercial aquaculture (Eding and Kamstra, 2001; Pruszyñski, 2003).

In Nigeria, the present knowledge of the chemical proximate composition of fish species from Nigerian  waters is very limited. Most of the work done so far has focused primarily on proximate analysis. While this is also an important factor of nutrition, it does not directly address the health value of the fish, with respect to its fatty acid profile. In this study, wild and cultured African catfish were analyzed to determine the composition and relative abundance of fatty acids

in their muscles.

1.1        STATEMENT OF PROBLEM

The major factors that affect the nutritive value of fish products are related to how fish is

handled, processed or preserved, and stored. Traditional practices such as exposing fish for long periods to weather elements coupled with traditional methods of preservation (hot smoking, sun-drying, and deep frying) and poor storage are subjecting fish to different kinds of degradation. Because of the high unsaturated fatty acid content of fish, free radical oxidation is a common phenomenon in all types of fish products (fresh or processed) that are exposed to air (Ashton, I.P 2002) Photosensitized oxidation is also a problem in sun-dried products while enzymatic oxidation is likely to be more pronounced in fish products that are partially processed (Thunberg, 1787).

 

 

 

 

 

1.2       JUSTIFICATION

 

       The nutritional consequence of marine food has increased widely because of the beneficial effects of eating marine food. Marine food is also one of the most important sources of high-protein and highly digestible protein and a superior source of essential minerals. In general the fish has a standard valuable source of elevated value of protein in the human diet. In recent years, fish fats have also assumed huge nutritional significance due to their protective role against the development of cardiovascular disease and rheumatoid arthritis.

 

1.3       SCOPE

  • Just a single species of cat fish is to be used for this study
  • The protein and fatty acid content of both fresh and smoked fish is to be analysed.

 

1.4       AIMS AND OBJECTIVE

1.4.1    AIM

To determine the content of protein and fatty acid on catfish.

1.4.2    OBJECTIVES

i            To compare the protein and fatty content of fresh and smoked cat fish

  1. To determine whether or not the processing of fish by smoking affects the protein and fatty acid content.

iii.         Evaluate the sensory attribution of the smoked and fresh cat fish.