Catfish (order Siluriformes) are a diverse group of fish. They are named for their prominent barbels, slender, whisker-like tactile organs near the mouth, which give the image of cat-like whiskers.
Catfish are very diverse, ranking second or third in diversity among orders of vertebrates, with almost three thousand (3,000) known species. About one in every ten species of fish, and one in every twenty (20) vertebrates, is a catfish.
Catfish are found primarily in freshwater environments of all kinds, with species on every continent except Antarctica. Some species from the families Ariidae and Plotosidae are also found in marine environments. They feature some of the smallest known vertebrates, including the candiru (toothpick fish), the only vertebrate parasite to attack humans, as well as Mekong giant catfish, the largest reported freshwater fish.
Catfish include bony-plated types and also smooth, naked types, but they do not have scales. Not all catfish families have prominent barbels; what defines a fish as being in the order Siluriformes are certain features of the skull and swimbladder.
Catfish is a source of rich, cholesterol-free, and special type of easily digested animal protein that is increasingly being recommended over red meat.
Nigeria is the world's largest producer of catfish, one of the most commercially important freshwater fish species in Africa. Catfish is the most popular fish on the local market. There is also a substantial trade in smoked fish to neighbouring countries and Nigerians in the United States, Europe and the Middle East.
Smoking is the major preservation methods of catfish farming and inland fishery.
The usual practice is to suspend catfish over fire in a traditional mud smoke house or kiln. Uncontrolled burning of wood during the process results in products which are often charred and brittle. The shelf-life of catfish is enhanced by hot smoking at the expense of the nutritive value.
TYPES OF CATFISH SMOKING
Cold Smoking: The catfish temperature does not exceed 30°C so that the flesh remains uncooked. The flavor of smoke is thus imparted to the product without much thermal damage to the nutritive value of the catfish.
Cold-smoked catfish will not keep long at ambient temperature and should be frozen if there is need for storage. Cold-smoked catfish has the following benefits over hot-smoked catfish:
High nutritive value
In the market, cold-smoked catfish should be displayed in cabinets maintained at temperature of 0°C or be placed on metal trays embedded in ice and screened from flies.
Hot Smoking: During hot smoking, the catfish is cooked therefore the temperature is allowed to rise to about 80°C. It is traditional smoking in tropical countries and offers extended shelf-life.
The primary aim of hot smoking is to preserve the product’s flavor and colour arising as a result of the preservation function. In an attempt to produce the product safe from mould, fragmentation and bacteria infestation during short term storage at ambient tropical temperature, the catfish may be so dried as to become charred or brittle.
Such poor quality product rarely appeals to consumers and hardly fetches good price at the market.
The basic unit operations involve in the production of smoked catfish from catfish is highlighted below
The fishes are bled, gutted and gilled to remove the agent of deterioration by using clean knife.
The cleaned fish are soaked in salt solution (30% salt)
The heating chamber is filled with charcoal and charge by fire. The cleaned or treated fish is loaded into trays and feed into the kiln. Drying is considered adequate when the moisture content has been reduced to about twenty-five percent (25%).
The smoked fish is package neatly in transparent cellophane nylon ready for sales.
The market prospect of catfish cuts across the whole country. But foremost consumers are the restaurants, households, beer parlours, hotels, and individuals. Nigeria with a population of over two hundred million (200,000,000) people is estimated to consume about one million, five hundred thousand (1,500,000) metric tonnes of fish per annum.