NUTRIENT COMPOSITION AND MICROBIAL LOAD OF SMOKE-DRIED CATFISH (CLARIAS GARIEPINUS) IN UMUAHIA METROPOLIS

ABSTRACT

This study was aimed at assessing the nutrient composition and   microbial quality of smoke-dried catfish in Umuahia metropolis. Fresh catfish samples from Orpet satellite market were purchased and experimentally smoked using a smoking kiln and this served as control (sample A). Smoke-dried fish obtained from Orie-Ugba and Ubani markets designated as sample B and C, respectively were purchased from fish processors after 3days of smoking. The control and market smoke-dried catfish were used to determine the nutrient composition and microbial load using standard procedures. Data used were represented as means (SD). The moisture content ranged from 8.50% to 8.52%, protein content (34.63% to 36.74%), carbohydrate (29.24% to 31.84%), while ash content was from 2.76% to 2.83%. crude fubre ranged from 1.77% to 1.86% and fat content (22.10% to 22.99%). The vitamin A content ranged from 47.10 to 48.33mg/100g, iron content ranged from (11.83 to 12.31mg/100g), zinc content ranged from (1.01 to 1.04mg/100g), calcium (8.96 to 9.23mg/100g), magnesium (26.27 to 27mg/100g) potassium (207 to 213mg/100g) while iodine ranged from 0.011 to 0.018mg/100g. Microorganisms isolated from smoke dried samples were identified as Staphylococcus aureus, Rhizopus spp, Salmonella spp. and Klebsiella spp. The lowest mean microbial count was 23.5cfu/g for the smoke-dried catfish (control), while the highest count of 315cfu/g was from Orie-Ugba (sample B) and Ubani (sample C) markets each. The low microbial load of the control samples guarantees fish quality and safety to consumer. Based on findings, the smoke-dried catfish samples were found to be good sources of nutrients and are microbiologically safe for consumption.

TABLE OF CONTENTS

LIST OF TABLES

LIST OF FIGURES

Figure 2.1       An oil drum modified for use as smoking kiln             24

Figure 3.1:     Flow chart showing smoke-drying of fresh catfish (control)             28            

CHAPTER 1

INTRODUCTION

Fish contributes to the nutritional security of poor households in developing countries in various ways. These include a consumption pathway (where direct consumption of fish boosts intakes of micronutrients and omega-3 oils) and a cash-income pathway (where commercialization of fish contributes to wider product distribution, economies of scale and higher overall food consumption) (FAO, 2012). The importance of including fish in a healthy diet is related to its unique nutritional value, increasing evidence shows the role of fish in our diets by replacing less healthy foods. Fishes are healthy and good alternative to meat products (Glover-Amengor et al., 2012). One of the major ways of adding values to fish in the tropics is by smoking and drying. Drying is the process of removing moisture contained in a product in order to reduce considerably the reactions which lead to the products deterioration. The water is eliminated by evaporation into the surrounding air by activated energy; various equipment has been developed for dehydration of food products. Such equipment includes dryers, oven and kilns (Olayemi et al., 2013).

Catfish (Clarias gariepinus) has been reported to be a very important fresh water fish in Nigeria (Abdullahi et al., 2001). It has enjoyed wide acceptability in most parts of the country because of its unique taste, flavor, and good texture (Abdullahi et al., 2001). It is widely distributed, extensively cultivated in ponds (Abdullahi et al., 2001). Fish is one of the best sources of proteins, vitamins and minerals and essential nutrients required for supplementing both infants and adult diets (Abdullahi et al., 2001).

Post-harvest fish losses occur globally in all fisheries, from the point of production to the final sale to the consumer, but the magnitudes and types vary (Akande and Diei-Ouadi, 2010). As in any food system, losses of fish affect the four dimensions of food security: availability, access, stability and utilization (Akande and Diei-Ouadi, 2010). The socio-economic impact of post-harvest losses is significant because the post-harvest domain comprises several activities at all stages of the supply chain, including handling fish on board, unloading, processing, storage and distribution (Akande and Diei-Ouadi, 2010).

In Nigeria, it has also been noticed that fish is eaten fresh, preserved or processed (smoked or dried) and form a much-cherished delicacy that cuts across socio-economic, age religious and educational barriers (Adebayo-Tayo et al., 2008). Poor post-harvest technology (handling, preservation and processing) have been reported earlier to have the ability to cause unhealthy situation resulting in massive spoilage (Akande, 1996). To reduce the loss associated with such spoilage, preservation methods such as smoking, salting, sun drying, freezing and cold storage are employed (Eyo, 2001 and Olokor et al., 2007). Smoking of fish from smoldering wood dates back to early civilization (Eyo, 2001 and Olokor et al., 2007). About 66% of preserved fish in Nigeria are smoked. Smoking is the traditional method of fish preservation in many developing countries (Tawari and Abowei, 2011). Smoking is desirable partly due to the ease of the procedure, and consumer preferences (Sengor et al., 2004, Olokor et al., 2007, Abolagba and Igbinevbo, 2010).  Wood smoke gives fish a desirable taste, toughens and dehydrates fish muscle providing a longer shelf life, lowering the pH making it less susceptible to spoilage (Sengor et al., 2004, Olokor et al., 2007, Abolagba and Igbinevbo, 2010).

1.1 Statement of the problem

Fish provides 34.7% of the dietary intake of animal protein to the average Nigerian (FAO, 2009a). Catfish accounts for 70% of fish production from aquaculture in Nigerian (FAO, 2007). Farmed and wild Clarias gariepinus are good source of nutrients for human consumption (Nwali et al., 2015). Fish smoking is one of the traditional fish processing methods aimed at preventing or reducing postharvest losses. Smoked African catfish are also in high demand because they can be stored for longer periods without power while retaining nutritional quality (FAO, 2010). Smoking involves heat application to remove water and it inhibits bacterial and enzymatic actions of fish (Kumolu-Johnson et al., 2009). Abolagba and Iyeru (1998) reported that improper smoking and unhygienic handling of smoked fish results in high microbial infestation and that storage temperature close to 37^oC is deal for the growth of pathogenic bacteria. They also stated that high humidity and high to moderate temperature support mould growth in stored foods. Moulds produce mycotoxins some of which are carcinogenic while fungal groups may cause mycoses and allergies in man (Abolagba and Iyeru, 1998).

Microbial contamination of smoked fish has been found to be due to several factors such as poor smoking of fish products (i.e. inappropriate temperature control or application), poor personal hygiene of processors/seller, poor hygiene/sanitary practices relating to smoked fish products, smoke/workhouse, packaging and storage as well as the use of inadequate and inefficient traditional processing facilities (Abolagba et al., 2011). Poor environmental sanitation and high human traffic are also implicated (Abolagba et al., 2011). This work was therefore conducted to determine the nutrient composition of smoke- dried catfish (Clarias gariepinus) and also determine the microbial load in smoked-dried catfish (Clarias gariepinus) sold at the markets in Umuahia metropolis, Nigeria.

1.2 Objective of the Study

The general objective of this study is to determine the nutrient composition and microbial content of catfish (Clarias gariepinus).The specific objectives include to:

i. determine the proximate, vitamin, and mineral composition of catfish (Clarias gariepinus)smoked in different locations.

ii. identify the microbial load and microbial quality of smoked catfish (Clarias gariepinus).

iii. evaluate differences in parameters of catfish smoked at different locations.

1.3        Significance of the Study

This study will help to provide information on the nutrient content of smoked catfish (Clarias gariepinus). It will also inform people of the importance of following hygienic procedures when smoking catfish traditionally and also people will be informed of the dangers associated with improper preparation of catfish through traditional smoking methods. The result will also help the extension workers to educate households on the smoking methods that will retain the nutritional value of the catfish while preserving it as well as reduce post-harvest loss. 

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