EFFECT OF PRESERVATION OF FISH TECHNIQUES INOCULATED WITH D. MACULATES

EFFECT OF PRESERVATION OF FISH TECHNIQUES INOCULATED WITH D. MACULATES

CHAPTER ONE

1.0     INTRODUCTION

Fish are an important resource for humans worldwide, especially as food. Commercial and subsistence fishers hunt fish in wild fisheries (fishing) or farm them in ponds or in cages in the ocean (aquaculture). They are also caught by recreational fishers, kept as pets, raised by fish keepers, and exhibited in public aquaria. Fish have had a role in culture through the ages, serving as deities, religious symbols, and as the subjects of art, books and movies.

There are different species of fish but my main concern in on Clarias commonly known as catfish. They are found in inland waters and is one of the most widespread catfish genera in the world. The genus is found in Southeast Asia and East Asia westwards through India and the Asia Minor to Africa. The diversity of these catfishes is highest in Africa. Some (notably the walking catfish) have become pest species where they have been accidentally introduced.

Clarias species are recognized by their long-based dorsal and anal fins, which give them a rather eel-like appearance. These fish have slender bodies, a flat bony head, and a broad, terminal mouth with four pairs of barbels. They also have a large, accessory breathing organ composed of modified gill arches. Also, only the pectoral fins have spines.

Salting is the preservation of food with dry edible salt. It is related to pickling (preparing food with brine, i.e. salty water), and is one of the oldest methods of preserving food. Salt inhibits the growth of microorganisms by drawing water out of microbial cells through osmosis. Concentrations of salt up to 20% are required to kill most species of unwanted bacteria. Smoking, often used in the process of curing meat, adds chemicals to the surface of meat that reduce the concentration of salt required. Salting is used because most bacteria, fungi and other potentially pathogenic organisms cannot survive in a highly salty environment, due to the hypertonic nature of salt. Any living cell in such an environment will become dehydrated through osmosis and die or become temporarily inactivated. Available water is necessary for the microbial and enzymatic reactions involved in spoilage. There are a number of techniques that have been or are used to tie up the available water, techniques such as drying, salting and smoking have been used, and have been used for thousands of years. In more recent times, freeze-drying, water binding humectants, and fully automated equipment with temperature and humidity control have been added. Often a combination of these techniques is used.

 1.1 WHY AND HOW DOES FRESHLY CAUGHT FISH SPOIL?

Freshly caught fish spoil easily and need to be properly preserved. The three most popular methods of fish preservation are sundrying, smoking, and sundrying. Top quality fresh fish are essential for fish preservation. Of all flesh foods, fish is the most susceptible to tissue decomposition, development of rancidity, and microbial spoilage. Keep freshly caught fish alive as long as possible. A metal link bag will permit fish to remain alive longer in the water than a stringer. Spoilage and slime-producing bacteria are present on every fish and multiply rapidly on a dead fish held in warm surface water. Fish begin to deteriorate as soon as they leave the water. To delay spoilage, clean the fish as soon as possible. Thorough cleaning of the body cavity and chilling of the fish will prevent spoilage. Fish spoilage occurs rapidly at summer temperatures; spoilage is slowed down as freezing temperatures are approached.

1.2  INFESTATION OF D.MACULATES ON FISH

Blatchford (1962) observed that insect infestation is more likely to occur on fish under the influence of warm temperature and high moisture content. The studies have been recorded mainly with the biology of D.maculates as Usip and Etimibe 38 a pest of smoked fish. Lale and Sastawa (1996) and Odeyemi et al. (2000) put the losses due to susceptibility to pest infestation and deterioration of smoked fish products at 50% during storage, leading to reduction of nutritive quality of smoked fish. Eyo and Mdaihli (1997) stated the control measures against insect infestation of smoked fish which include preserving in the oven at a minimal temperature and also the use of harmful chemical insecticides such as heptachlor to keep away insects and other pests. Spoilage is a metabolic process that causes food to be undesirable or unacceptable for human consumption due to changes in sensory nutritional characteristics (Doyle, 2007). Since fish is highly susceptible to deterioration immediately after harvest and to prevent economic losses, the processing and preservation of fish is of utmost importance (Okonta and Ekelemu, 2005). Odeyemi (2000) noted that smoke-dried fish is one of the highly digestible and respectable sources of proteins and essential minerals in the tropics but it is highly susceptible to insect pest infection. In recent years, there have been increasing and concerted efforts directed at developing natural pest management control agents that are relatively cheap, safe, biodegradable and environment friendly as alternatives to synthesized insecticides (Boeke, 2001). Ayuba and Omeji (2006) stated that the gap between demand and supply of fish is widened due to poor post-harvest handling, lack of processing and storage facilities. The Dermestes species eat away the muscles leaving the skeletons when cured fish are stored for long periods. Lale and Sastawa (1996) and Odeyemi et al. (2000) put the losses due to susceptibility to pest infestation and deterioration of smoked fish products as 50% during storage, leading to reduction of nutritive quality and market price of smoked fish. Oke et al.(2014) reported that the nutritive benefit of cat fish C.gariepinus (Burchell,1822) are threaten by its infestation by D.maculatus (Degeer,1774) during storage. Certain factors affect the development of insect pests in smoked fish such as salt content, moisture content, temperature, etc. It is of great importance to note that the most important environmental factors that affect pest development are ambient temperature and humidity.

1.3 IMPORTANT OF FISH PRESERVATION

1. Fish is very fast rotting being. So drying is must to keep them free from rotting.
2. Drying fish has a great demand in the market. It also help to meet up the fish or protein demand.
3. Nowadays drying fish is also being used as nutritious protein food for poultry.
4. Dried fish stays for long time

5. As the drying weights less so, it cost less while transporting.
6. It is become not possible to consume or sell all fish then drying is a suitable way for preserving.

1.4     STATEMENT OF PROBLEM

Because of improper care taken during fish preservation techniques we face so many problems such as: The suitability of salt for any particular application depends upon several factors, the most important of which are:

(i) The chemical composition;

(ii) The microbiological purity;

(iii) The physical properties.

Chemical composition

Commercial salts vary widely in their composition; high quality salt may contain 99.9 per cent sodium chloride, whereas low quality salt may only contain 80 per cent sodium chloride. Apart from contaminants such as dust, sand and water, the main chemical impurities of commercial salts are calcium and magnesium chlorides and sulphates, sodium sulphate and carbonate, and traces of copper and iron. Solar salts tend to be less pure than mine-evaporated salts.

1.5 OBJECTIVE OF THE STUDY

This research work is intended carry out for the following:

1. To determine the effect of preservation of fish techniques inoculated with D. maculates
2. To identify the best techniques or method of preservation of fish for human consumption.
3. To identify the most hygienic ways of preservation of fish and fungus associated with fish preservation. .

1.6     SIGNIFICANCE OF THE STUDY

 Fresh fish handling procedures encompass all the operations aimed at maintaining food safety and quality characteristics from the time fish is caught until it is consumed. In practice, it means reducing the spoilage rate as much as possible, preventing contamination with undesirable microorganisms, substances and foreign bodies and avoiding physical damage of edible parts.

The immediate effect of fish handling procedures (e.g., washing, gutting, chilling) on quality can easily be assessed by sensory methods. Fish quality, in terms of safety and keeping time, is highly influenced by non-visible factors such as autolysis and contamination and growth of microorganisms. These effects can only be assessed long after the damage has occurred, and the proper procedures must thus be based on knowledge about the effects of the many different factors involved. Large or small improvements are usually feasible when analyzing current fish handling methods.

1.7     LIMITATIONS OF THE STUDY

Several factors which affect the rate at which salt is taken up and water is replaced in fish are:

1. Environmental factors such as humidity, temperature, sunshine, raining season and human factor.
2. The thicker the fish, the slower the penetration of salt to the centre.
3. The higher the temperature, the more rapid the salt uptake.
4. The higher the salt concentration, the more slowly the fish dries;