Processing of fish deals with the processes associated with fish and fish products between the time fish are caught or harvested, and the time the final product is delivered to the customer. Although the term refers specifically to fish, in practice it is extended to cover any aquatic organisms harvested for commercial purposes, whether caught in wild fisheries or harvested from aquaculture or fish farming.
Larger fish processing companies often operate their own fishing fleets or farming operations. The products of the fish industry are usually sold to grocery chains or to intermediaries. Fish are highly perishable. A central concern of fish processing is to prevent fish from deteriorating, and this remains an underlying concern during other processing operations.
Fish processing can be subdivided into fish handling, which is the preliminary processing of raw fish, and the manufacture of fish products. Another natural subdivision is into primary processing involved in the filleting and freezing of fresh fish for onward distribution to fresh fish retail and catering outlets, and the secondary processing that produces chilled, frozen and canned products for the retail and catering trades.
Some of the aspects of fish processing include[v]
- Fish Canning– Canning is a modern technological advancement in food processing that improves the shelf life of the fish enabling its storage for several years. The canning process involves hermetically sealing the product in a container, heat sterilizing the sealed product, and cooling to room temperature for storage. An example is a popular sardine.
- Mince Fish– Mince fish are fish flesh separated from the skin and bones. Separating methods may be mechanical using deboning machines or combined chemical and physical methods. The separated flesh could be processed into delicate fish products such as fish fingers, fishcakes, fish sausages which are sold frozen or partly filled in oil.
- Fish Silage-Fish silage or liquefied fish protein is a mixture of fish liquid by enzymes in the presence of an acid. This simple technique of processing fish or fish waste into silage is scarcely utilized in developing countries because acids have to be imported. The raw material for silage production can be provided locally from the following:
. Catches from another fishery
. Artisan seasonal glut
. Products of fish processes.
This serves as an excellent livestock feed. - Fish Meal-The production of fishmeal and oil is the predominant method of processing the world’s supply of non-edible fish and fish frames from filleting operations with the oil used in the leather, soap, and pharmaceutical industries, and the residue as a source of quality fertilizer and livestock feed. This is achieved using the wet process or dry process.
- Other processing and storage mechanisms include drying, smoking, salting, roasting, frying, cooking, chilling and freezing among others.
STEPS INVOLVE IN FISH PROCESSING
Fish processing is a value addition process which involves several precautions to ensure food safety. Several requirements have been put in place to ensure processing facilities meet up with internationally accepted practices of food safety. Click here to read more
PRE PROCESS OPERATIONS
There are many types of fish products available to the consumer but most of them will have undergone some sort of initial preparation before processing. This preparation can be in the form of stunning of fish, grading, removal of slime and cutting the fish in a particular way to produce the raw material necessary for future processing. Due to the delicate nature of the fish and the rapid rate of deterioration that can occur if the fish is treated badly, it is extremely important to handle it hygienically and carefully during all stages of preparation.
Stunning of fish
Stunning of freshly caught fish or fish delivered live to a processing plant is best done with an electric current. First, the fish are placed in a tank of water and an electric current is then passed through the water to stun or kill the fish. Live fish are also slaughtered by cutting the aorta and bleeding to death. In some plants, water in the fish tank is saturated with carbon dioxide or salt, which renders the animals unconscious or dead.
Grading of fish
Sorting by species or on the basis of freshness and physical damage are still manual processes, but grading of fish by size is easily done with mechanical equipment. Size grading is very important for fish processing (i.e., smoking, freezing, heat treatment, salting, etc.) as well as for marketing.
Removal of slime
Slime accumulating on the skin of dying fish is a protection mechanism against harmful conditions. In some fish species, slime constitutes 2-3% of body weight. Slime creates a perfect environment for microorganism growth and should be removed by thorough washing. Soaking fish in a 2% solution of baking soda and then washing in a cylindrical rotating washer can remove slime from freshwater species.
Splitting, gutting and filleting.
There are several reasons why we cut and gut fish.
1. To add value to the product (e.g. making fillets);
2. To make the product acceptable to the customer;
3. To maintain the quality by reducing spoilage;
4. To make further processing easier;
5 To reduce processing costs;
6. To improve storage life; and
7. To reduce transport costs/charges.
Splitting
Splitting or opening the fish is usually done if the fish is to be salted, dried or smoked. It increases the cut surface area that is exposed to the air and decreases the thickness of the fish, so drying is faster,
Cutting and Gutting
Cutting and gutting is done to help reduce spoilage, as guts are full of bacteria and enzymes, and are not usually eaten. Making a ventral cut from the gill to the anus, pull out the guts with the fingers and thoroughly wash out the cavity.
These processes generally take place within separate areas of the fish processing plant. The fish are kept on ice in boxes before being delivered to the fish processing plant until required for further processing.
This can be processed into fillet or smoked.
Smoking and Drying of Fish
There are 2 major ways by which catfish can be dried. They are:
1. The traditional open fire with either firewood or charcoal as the fuel
2. Kiln (oven) with either electricity, gas, wood or charcoal as the source of heat.
One advantage of the open fire over the gas oven is that the set up cost is lower. However, the advantages of the kiln over the open fire are numerous and include temperature regulation, even distribution of heat, less contamination of the fish with the cancer causing Polycyclic Aromatic Hydrocarbons (PAHs), versatility of fuels for combustion to mention but a few.
Traditional Open Fire Method
I believe it is was from this method that the term “smoked catfish” was coined. This is because, with this method, the heat required is quite low (as opposed to regular cooking heat) and most times there’s a lot of smoke during the process. This is the most common method of drying fish in Nigeria and it involves the drying of the fresh fish on a smoking grate (smoking rack) with a bit of heat underneath from the burning of wood or charcoal. The rack might be placed on an open metal barrel or a mud structure. Ensure that the rack is slightly oiled before putting the fish on it and do not stack the fish on each other as this would make sum dry before others. Start a fire beneath the smoking rack and ensure that the heat is low especially for the first two hours .
After the first two hours, you can increase the heat slightly. The drying time depends on the thickness of the fish, nature of the fuel, customer demand and weather. Avoid using wood or saw dust as these generate a lot of smoke while drying. The generated smoke if too much can cause the fish to be bitter and increase the concentration of the cancer causing PAHs. Charcoal is the preferred option.
This method requires the regular flipping of the fish from one side to another in order to ensure that all parts of the fish are properly dried.
Kiln (Oven) Method
This is the future of fish smoking because it’s faster, healthier, neater, more environmentally friendly and has more capacity than smoking over an open fire. However, it is more expensive to set up. Generally, most kilns use gas with the option of electricity, charcoal or wood. Some extra features such as a thermometer (to monitor the temperature), blower (for proper heat distribution), and insulation (to prevent heat loss) can be added at your behest, and that would cost you extra. These extras will reduce your drying time, ensure even output as well as reduce the effort required to dry the fish. My kiln has all the above features so once i put everything in motion, i can spend up to three hours without checking on the fish in the kiln.
Like the traditional method, you need to oil the smoking racks before stacking the fish. You put on the gas from beneath and adjust the flow of the gas to control the heat in the kiln. The ease of control that you have over the amount of heat in the kiln is another advantage of the kiln over the traditional open fire. There is no need to keep flipping the fish from side to side unlike the open fire method, especially if your kiln is fitted with a blower. Oven dried catfish generally last longer than open fire dried catfish because the heat is more evenly distributed throughout the fish (from the inside to the outside). You can use charcoal during the last one hour of drying to give your fish the “local aroma”.
As stated earlier, the drying time would depend on the thickness of the fish, nature of the fuel, customer demand and weather.
Image by: David Galadima
Image by:Dvid Galadima
Market and Marketing
As with the fresh catfish, the market for the smoked catfish is also very large. One reason for this is that no major tribe or religion forbids the consumption of smoked catfish. Also, there are no age or gender restrictions to the consumption of smoked catfish. This means that you potential market in Nigeria alone is over 100 million! This is excluding Nigerians in diaspora. Once the fish has been properly smoked, it should be packaged according to the needs of the customer. For example, a big hotel or restaurant will require large quantities of smoked catfish at once and might not focus too much on packaging. In this case, a carton will be the best way to sell and transport it to them.
On the other hand, a supermarket might require a different type of packaging. As for where to sell your smoked catfish, you can always start with selling to family and friends who will ultimately refer you to other people and businesses. Local hotels and restaurants are also places where your fish can be sold. Packaged smoked catfish can also be included in hampers and given as gifts during festive seasons.
As for how much to sell your smoked catfish for, first find out the cost of producing the smoked catfish including cost of firewood or gas, packaging, etc. When this is done, try to compare your price with the average market price. If your price is higher, look for innovative ways to reduce your cost of production. This might mean buying from a fish farm directly instead of from a fish market. Sometimes (especially when you use an oven), your price will be higher than those sold in the market. It is left to you to make your customers understand the quality they are getting when they buy from you. Also note that properly dried fish will lose between 70–75% of its body mass so factor this into you cost analysis and other calculations.
REFERENCES
[i] Culled from: FAO 2012 The State of World Fisheries and
Aquaculture
[ii] Clucas, I.J. 1981. Fish handling preservation and processing in the tropics: Part I. Report of the Tropical Development and Research Institute, G 144, VIII+ 141 PP.
[iii] Akinola, O.A., A.A. Akinyemi, and B.O. Bolaji, 2006.Evaluation of traditional and solar drying systems towards enhancing fish storage and preservation in Nigeria (Abeokuta LocalGovernment as a case study). J. Fish. Int., 1(2-4): 44-49.
[iv] Okonta, A.A. and J.K. Ekelemu, 2005. A preliminary study of micro-organisms associated with fish spoilage in Asaba, Southern Nigeria. Proceedings of the 20th Annual Conference of the Fisheries Society of Nigeria (FISON), Port Harcourt, 14th-18th November, pp: 557-560.
[v]https://maxwellsci.com/print/ajas/v3-437-452.pdf
[Vi] https://davidgaladima.medium.com/catfish-102-smoking-and-drying-b51595d7de82
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