Smoking is undeniably one of the oldest methods of food preservation and can be said to be as old as cooking with fire.
Smoking fish enhances its flavour and colour. Fish smoking is one of the most widely used traditional processing methods in Ghana. Research indicates that about 80 per cent of fish in Ghana is processed through smoking.
It is also interesting to note that most Ghanaians prefer consuming smoked fish compared to the other preservation methods. This observation is not only peculiar to Ghana, but in Europe as well, where about 15 per cent of total quantity of fish for human consumption is smoked prior to release to the market.
Consumption of smoked fish has increased over the years in Ghana, with salmon leading as the most consumed smoked fish followed by herrings (amane) and mudfish (adwen).
Smoking as a method for preserving fish is done to prevent spoilage, prolong the shelf life and improve the quality of the fish. Other reasons, for smoking may include prevention of post-harvest losses, as well as easy transportation and storage.
Apart from its high quality protein, fish in itself contains important fatty acids and micro nutrients. It contains Omega-3 fatty acid which protects the heart against erratic cardiac disturbances including lowering of blood pressure and heart rate and improvement in the function of the blood vessel. Omega-3 also helps in lowering triglycerides in the blood which may ease inflammation.
Some have argued that smoked fish contains less omega-3 compared to fresh fish. However, some scientific reports have concluded that this is not always the case as some studies have reported omega-3 contents in smoked fish not to be too different in the fresh fish. The strong and consistent evidence for the benefits of fish is such that the Dietary Guidelines from the American Heart Association and others suggest that everyone eats fish at least twice a week.
Fish makes up about 60 per cent of animal protein in Ghanaian diets. Data available suggests that, the average per capita intake in Ghana was estimated at 27kg in 2011, with the world average pegged at 20kg whilst that for Africa at 10kg, indicating clearly the high consumption of fish in Ghana. According to the Food and Agricultural Organisation report of 2016, fish makes up about 22 per cent of food expenditure in all households and 26 per cent in poor households.
In smoking fish, the use of fuel in the form of wood is the main and common source of energy. It must be noted that different woods may affect the quality of the smoked fish differently consequently having the tendency to affect the flavour. Smoke from wood is composed of vapours and particles that are easily taken up by moisture on the surface of the fish during smoking, hence contributing to the characteristic smoke smell and colour.
According to a scientific journal publication, the fuel wood preferences of most fish smokers are also related to the physical characteristics of the wood and how they affect the smoked product.
moking fish is usually characterised by these five steps; Product preparation, Salting or brining, Equilibration and drying, Smoking, Product packaging and storage.
The smoking process imparts colour and flavour to the fish due to the deposition and oxidation of phenol. It also enhances bactericidal properties due to chemical constituents such as formaldehyde and acetic acid which can prevent fungal growth and inhibit viral activities in the fish. Smoking also prevents the production of toxins by Clostridium botulinum, however, some researchers from the University of Ghana and Gent University recorded high levels in samples of smoked fish from processing points and the informal market. Chemicals such as 2, 6-dimethylphenol, 2, 6-dimethoxy-4-methlphenol and 2, 6-dimethoxy-4-ethylephenol which may also be found in smoked fish carries antioxidant properties.
Besides the beneficial compounds mentioned earlier, carcinogenic compounds have also been seen to be present in smoked fish. However, depending on the method used for smoking, the amount present varies. Among these compounds is the Polycyclic Aromatic Hydrocarbons (PAH). The Polycyclic Aromatic Hydrocarbons are formed by incomplete combustion processes which occur whenever wood, coal or oil are burnt. They occur as contaminants in the smoke.
A study to determine the effect of smoking process on PAHs content in smoked fish in Nigeria recorded high levels of PAH as a result of uncontrolled fish smoking practices that burn wood at higher temperatures, coupled with thermal pyrolysis of fat in fatty fish. Smoked fish contains elevated levels of nitrates and nitrites (nitrosamines) which are bi products of the smoking process. High levels are predisposing factors in breast and stomach cancers.
The deep flavours of smoked foods make them a delicacy among the gourmet inclined. While they may enjoy the satisfaction of the culinary delight, the long term health benefits need to be weighed. So, in view of the issues discussed above, the recommendation should be to consume smoked fish in moderation to achieve maximum benefit.
Consumption of about 50g twice a week should suffice. The skin of the fish may be removed before use to help reduce the amount and effects of PAHs present.
Additionally, smoked fish should be obtained from a well-controlled environment to reduce inadvertently consuming fish parasites leading to food poisoning.
The writers: Linda Denkyiraa and Freda Intiful are with the Department of Nutrition and Dietetics, University of Ghana