In Africa various traditional methods are employed to preserve, process and store fish for consumption and storage. These include smoking, drying, salting, frying and fermenting and various combinations of these. The advantages of smoking fish are manifold. Fish smoking prolongs shelf life, enhances flavor and increases utilization in soups and sauces. It reduces waste at times of bumper catches and permits storage for the lean season.
It increases protein availability to people throughout the year and makes fish easier to pack, transport and market. In Ghana, smoking is the most widely-used method practiced and is the most common activity for women in fishing communities. Practically all fish species available in the country can be smoked, and it has been estimated that between 70 and 80 percent of the domestic marine and freshwater fish catch is consumed in smoked form.
Traditional ovens have considerable disadvantages and were inefficient in capacity and fuel usage, causing poor-quality smoked fish and significant post-harvest losses. More fuel wood than necessary was used, contributing to forest depletion. Women suffered health risks from smoke inhalation, burns and exposure to heat. An improved fish smoking oven, developed by FAO and Ghana’s Food Research Institute of the Council of Scientific and Industrial Research (CSIR), was introduced in Ghana where it quickly became popular.
History of Chorkor Oven
The Chorkor was introduced in Ghana through training programs and promoted by the participatory approach. In each community, ten women were chosen as processors and involved from the outset in the implementation process, which ensured its high acceptance and adoption rates in the country. They had to provide the required quantity of mud and water to build the oven and participated in the construction of the oven base. One Chorkor oven was constructed for and owned by each of the ten processors. At least one mason and one carpenter were trained in each community to be responsible for the construction of additional ovens.
- Reduced consumption of wood, diminished forest degradation
- Better quality and value of fish smoked, improved marketability of the product, increased income, improved working conditions.
- Reduce health problems associated with inhalation of smoke.
The Chorkor oven became popular because of:
- Low construction costs
- Long life (8 years for a cement-faced mud oven, 4 years for bare earth oven if well-covered when it rains
- Large capacity (up to 18 Kg of fish per tray, with 15 trays per oven)
- High quality and uniformity of product due to greater retention of heat and circulation of smoke, reduced smoking time
- Ease of operation: no smoke in eyes, trays quickly changed, fireboxes very accessible
- Low consumption of fire wood
- Much less time and effort required for operation
Guidelines on the construction of the combustion chamber are given below:
1. General design
The combustion chamber, which is the base of the oven, is rectangular, about twice as long as wide, with two holes in front. The recommended standard measurements of the combustion chamber are: length=225 cm, width=112.5 cm, height=60 cm, wall thickness=12.5 cm, width and height of stoke hole=37.5 cm, depth of fire pit=15 cm. Preferably there should be a foundation sunk in the ground and a dividing wall in the middle which gives added strength to the oven, protects the median cross piece of the bottom tray from burning, gives greater support to the loaded trays, and allows for smoking of small quantity of fish over just one chamber, using less wood.
2. Materials – There are three appropriate approaches for construction of smoking ovens: clay mud, clay mud faced with cement, clay mud blocks sun dried or baked and mortar. Cement blocks is not recommended, since it cannot withstand the high smoking temperatures.
3. Procedures – First the ground is cleared and leveled, the outline of the oven walls is drawn and a trench 6-8Ã¢â‚¬Â deep is dug for the foundation. Next, the walls are constructed. For clay ovens, the holes are cut in the front wall once it is dry; for cement ovens, an arch is made. The last step is plastering.
4. Key point of design – The top of the oven must be square, level and flat, so that the wooden-framed trays can be put upon the walls.
Guidelines on the construction of the trays are given below:
- General design – For each oven there should be 12-15 smoking trays (with a total of 160-200 Kg of wet fish), plus several deeper storage trays.
- Materials – Ideally hard wood planks should be used for tray frame construction, but in practice softwoods are often used because they are less expensive.
- Procedures – Once the piece of wood are nailed together and the basic frame is made, a wire net is attached to the bottom edge to hold the nets firmly in place.
- Key point of design – The trays must be square and fit together in order to form a proper chimney.
Specific instructions on the smoking procedures are given below:
1. Acquisition of the fish
The final product is of greatest quality and has the longest shelf life when the fish is smoked fresh. Frozen fish can also be smoked while thawing. In some countries, post harvest processors smoke whatever is left over after a day’s selling. The resulting product is of poor quality.
2. Preparation of fish smoking – After degutting, fish is washed with fresh or salt water and carefully arranged on the trays.
3. The smoking
Depending on the type of fish being smoked (species, thickness, way of cutting it), its uses, and the length of time it has to be stored, the smoking process can take among 1 hour to 2 days, at temperatures above 80°C, which are high enough to cook the fish. Wet hot smoking usually takes about 1-2 hours and yields a moist, versatile product with about 40-55 percent moisture content but a limited shelf life of 1-3 days. Dry hot smoking, which is usually preceded by the former process, takes about 10-18 hours, sometimes days, yielding fish with 10-15 percent moisture content, sometimes even below 10 percent.
Fish smoked by this process have a shelf life of 6-9 months when stored properly. Fish is turned and the orientations of the trays are changed 2-4 times during the smoking cycle. The upper trays are placed close to the fire, while the lower ones are moved higher. After 2-5 hours of hot smoking, the contents of 2 or 3 trays of partly smoked fish can be combined in one tray. Then it can be smoked over a moderate fire (below 60°C) to continue the drying process. This second stage is the most important from a preservation standpoint, and may last as long as 2 days, yielding a very dry (10-15% moisture) product with a potential shelf life of 6-9 months.
4. The fire – Due to the chimney, formed by the staking of the trays on the oven and covered at the top, the heat and smoke constantly circulate inside.