CHAPTER ONE
INTRODUCTION
Stockfish is unsalted fish, especially stock dried by cold air and wind on wooden racks on the foreshore. The drying of food id the world’s oldest known preservation method and dried fish has a storage life of several years. The methods are cheap and effective in suitable climates the work can be dine by fishermen and family and the resulting product is easily transported to market. Stock is the most common fish used in stockfish production, while other whitefish such as Pollock,hardock, ling and cusk are used to a lesser degree.
Over the centuries, variants of dried fish has evolved. The (stock fish fresh dried not salted) category is after wrongly mixed with the chipfish, or salted stock, catgory where the fish is salted before drying. After 2-3 weeks in salt, the fish has salt matured and is transformed from wet salted fish to chipfish through a drying process . slting was not economically feasible until the 17th century, when cheap salt from southern Europe became available to the maritime nattons of Nothern Europe.
Fish supplies a good balance of proteins and minerals. It has relatively 10% calories hence its role in nutrition is recognizes (Akande and Tobor, 1992) fish and fish products constitutes more than 60% of the protein intake in adults especially in the rural areas (Adele 1992).
Fish is an extremely perishable food. It begins to spoil as soon as it is caught, perhaps even before it is taken out of the water. Spoilage proceeds as a series of complex enzymatic, bacterial and chemical changes that begins as soon as the fish dies. This why the fish becomes soft and the smell becomes more noticeable (Carruthers 1986) food preservation can be achieved by the removal of water from the food items since the microbial deteriogens require moisture for active growth including enzymatic hydrolysis of the food component (Ogbonna, 1987).
Water occurs naturally on the fish’s body and so drying is one of the simplest ways to preserve fish. It works by removing water from the fish which prevents the growth of micro-organism and decay. Drying food using sun and wind to prevent spoilage has been known since ancient times, water is usually removed by evaporation (air drying) but in the case of freeze drying, food is first frozen and then water is removed by sublimation. Drying creates a hard outer layer helping to stop micro-organisms from entering the food (Wikipedia 2009a). In other to prevent spoilage, the moisture content needs to be reduced to 25% or less. The percentage will depend on the oiliness of the fish or whether it has been salted, (Facts 2004).
Fish constitutes an important source of protein intake of many people, particularly in the developing countries. In Nigeria, where about 41% of the total animal protein intake is obtained from fishery products, the total fish consumption rates has risen to 2.66 million metrictons annually and it is reported that fish is a major source of animal protein and an essential food item in the diet of Nigerians because it is relatively cheaper than meat, fish contains most of the important essential amino acids, particularly, Lysine, Methionine and Tryptopham that are important for god living. Apart from its food value fish has been reported to posses medicinal values, such as, in the amelioration of asthma, arthritis, coronary heart diseases, goiter and cancer. Stock fish is highly desirable because of its enhanced flavor and texture in fishing addition to the protection offered by smoking against microbial, enzymatic and chemical detriotive alterations observed that smoking demonstrated a better efficient method of fish processing in terms of the retension of protein value and reduction in moisture content and is reported that smoke-drying had been used for centuries in preserving fish and is still widely used for this purpose among several communities in the third world where up to 70% of the earth is stock.
In many developing countries, stock fish are usually hawked without taking cognizance of the microbial contamination from the environment. In Nigeria, stock fish products contaminated with micro-organisms from the processing units and the market centres before reaching the consumers because many processors and hakers usually display them openly in a manner that could be potentially sources of microbial contamination.
The aim of these therefore is to isolate the possible micro-organisms associated with stockfish with a view to accessing the level of their public health implications.
Stock is the common name given to a genus of fish Gadus belonging to the family Gadidae and is also used in the common name of other variety of other fishes. It is whitefish referring to several species of the pelagic deep water fish with fins particularly stock (Gadus morhua) whiting (merlupinus) but also haxe (hrophycis) Pollock straight but often re-constituted. For centuries, it was preserved by drying as stockfish and cliffish and to added as a world commodity. During the drying about 80% of water in the fish disappears. The stockfish retained all the nutrients of the fish only concentrated. It is best known to be one of the richest sources of protein with the important B vitamin, Iron and Calcuim. Stock is moist and flaky when cooked and is white in color. It has a mid flavor, low fat content and a dense white flesh that flakes easily (Kurlausky, 1997). Stockfish is popular in West Africa where it is used in many soups that compliments the grain staples Fufu and Garri. The Bakweri, who are a fishing people of the English speaking part of Cameroon use stockfish in flavouring their palmnut or Banga soup which is called Kwacoco.
The name ‘Akporoko’ for stock fish among the Annng of Nigeria refers to the sound the hard fish makes in the pot and literally translates as that which produces sound in the pot (Wikepedia 2009b) Dried fish as a strong life of several years and thus, it gives Fungi: are omnipresent in the environment being found whereeva water, suitable organic nutrients and an appropriate temperature occur. They secrete enzymes outside their body structure and absorb the digested foods. The growth o filamentous fungi: in foods and food products results in waste and is costly as well as sometimes harzadous. Many different fungal species can spoil food product or produce mycotoxins or both (Anderson and Thrane 2006) mycoxins are secondary metabolites produced by moulds that are capable of causing diseases and deaths in humans and animals (Benneth and Klich, 2003), drying to moisture content below 15% prevents the growth of many spoilage organisms white mould growth is only suppressed at 10% moisture content (Bliere, 2005).
In a study of Mycoflora of smoke dried fish sold in Uydo, Eastern Nigeria by Adebayo-Tayo etal (2008), twelve different fungi were found to be associated with the smoke dried fish samples. The associated fungi: were Aspergillus Flauus, Aspergillus dereus, Aspergillus Fumigatus, Absidia Sp, Rhizopus Sp, Aspergillus niger mucor Sp, Penicillin talicum, P. viridatus, Candida tropicalis and Fusarium moniliformis.
Moulds may be present without producing any toxins (Benneth and Klich, 2003), but the presence of foxigenic production: Increases the risk for mycotoxin production (Jacobsen etal, 2008). Even though the fungus is no junaid etal 37 longer alive, white it was growing, if it is produced a mycotoxin it will have poisoned the food (Wong, 2007), mycotoxins greatly resist decomposition or being broke down in digestion so they remain in the food chain and even temperature treatments such as cooking and freezing donot destroy the mycotoxins. It has been proven that food items do carry residues of the toxins and thus it is certain that human beings are exposed to mycotoxins through contaminated food items among which fish is an important component (Adebayo –Tayo et-al, 2008).
AIMS AND OBJECTIVES OF THE STUDY
The major objectives of the study is as follows:
- To determine this microbial profile of stock fish head sold in Owerri, Imo State.
- To determine microbial isolates that can be found in stock fish heads sold in Owerri, Imo State.
- To make suggestions on how to safe stockfish head in Owerri, Imo State, is for human consumption.
JUSTIFICATION
Stockfish, especially the heads are common in the market. They are popular because of their rich taste and aroma and are sometimes eaten raw but mostly used in cooking most native soups. Moulds have been observed to grow on them and hence the need for this study to access if they are known mycotoxins producing species.
Stockfish belongs to the family Gadiadae and genus Gadus. Stock fish share the same family of monkfish and hadlock.it is omnivorous and feeds on salt eels, haddock, whiting, squid, small stock crabs, missels, lobsters, mackerel, worms and mullucs. It is usually 5l inches long and roughly cylindrical in shape. The body’s colour is greenish to brown with white belly and deis flaky flesh. It possesses a mild flavor when it is cooked; it could weigh up to 55 to 77 pounds. North Atlantic stock and pacific stock are the two common species of stock. Atlantic stock is found in cold water or deeper sea regions in North Atlantic whereas pacific stocks found in western and eastern regions of Northern pacific. Stock contains ample amounts of vitamin B12, Phosphorus, Selenium and protein. It also contains Potassium, niacin, vitamin B6, pantothenic acid, molybdenum and Omega 3 fatty acids
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