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This report has covered the following aspects of fermented fish processing and consumption in Burundi, Chad, Côte d'Ivoire, the Gambia, Ghana, Mali, Senegal, the Sudan and Uganda:
- literature review of microbiological and biochemical changes;
- sources and types of fish used; processing characteristics;
- storage and post-harvest losses;
- marketing and distribution;
- consumption patterns.
Fermentation is brought about by micro-organisms and enzymes present on the surface of the fish and in the guts before and after capture. Fermentative organisms may be introduced through the salt used or recycled brine. Salt is frequently used during curing to select desirable organisms in order to ensure that protein degradation is controlled without the production of toxic substances. Typical micro-organisms that have been identified are gram-positive halotolerant cocci, gram-negative halophilic rods and yeasts.
Fermentation results in chemical changes due to the breakdown of protein in fish muscle which produces trimethylamine, dimethylamine, ammonia, etc. In addition, fat oxidation takes place and other organic compounds are formed, including acetic acid and lactic acid. All these reactions result in changes in the texture, odour and taste of the final product. A peculiar characteristic of fermentation is a strong, sometimes offensive smell.
A wide variety of fish species from marine and freshwater sources was identified as raw material for fermentation. High-value dispersal are processed when quality deteriorates or they remain unsold and there are no ice or chilling facilities available. Pelagic species and clupeids which constitute the largest proportion of fresh fish supply to many people are also fermented. Underutilized species and by-catch from industrial trawling constitute another important source of raw material for processing.
In landlocked countries as well as regions with undeveloped marine fisheries, rivers and lakes provide the main source of domestic fish supply. The major freshwater species commonly fermented are tilapia, Alestes spp., Hydrocynus spp. and Nile perch.
The study revealed a wide range in the proportion of total domestic fresh fish supply processed into cured products. In West Africa and Uganda, for instance, more than 50 percent of the fish supply is smoked into various dried products. On average, about 10-20 percent of total domestic fish supply is processed into fully or partially fermented products by salting and/or sun drying.
A detailed observation of fish processing methods in many African countries reveals that many cured fishery products actually undergo some level of microbiological or biochemical degradation during curing or drying. These products possess a characteristic fermented flavour. Literature often only refers to Southeast Asian fish pastes and sauces as fermented products. However, various types of fermented fishery products are now known to be processed and consumed in many African countries. Indeed, curing by salting, fermentation and drying constitute the second most important method of preserving fish in Africa after smoking.
Three methods of fermented fish processing were identified, namely salting and drying, salting without drying and drying without salting. The resultant product may be firm and semi-dry, wet and soft or hard and dry respectively. The predominant processing method in a country depends upon socio-cultural factors, food habits and the availability of salt. In coastal countries with readily available or cheaper sources of salt, fermented products are usually heavily salted.
Unlike Southeast Asian products, fermented fishery products in Africa usually remain whole and firm after processing. The fermentation period is comparatively short, hence the fish muscle does not break down. In some cases whole species are cured and the product retains most, if not all, of its original features so that the species can be easily identified. Fermentation is sometimes unintentional and an incidental process, especially during sun-drying.
Fish processing in Africa is largely an artisanal activity involving individuals or family units. Consequently, documented or formal quality standards and controls are absent. All kinds of raw fish, irrespective of quality, are processed into fermented fish. Hygienic standards are generally poor but there are very few reports of food poisoning due to fermented fish consumption.
Processing equipment such as fermentation tanks, drying racks and packaging containers are locally available, cheap, easy to construct or repair and reusable.
Fermented fishery products are susceptible to spoilage through mould or bacterial decay, insect infestation or fragmentation. Their shelf-life depends on salt and moisture contents. A well dried product with a high salt level can be stored for 6-12 months. Semi-dry or wet products keep for one to three months. The most widespread method of preventing deterioration is redrying or storing in dry salt. The use of organic insecticides for preservation is not a common practice, except in Mali and Malawi where some chemicals are officially permitted. However, there are some reports of uncontrolled application of insecticides to fermented dried fish to control insect infestation in some countries.
Trade is mainly informal and is important for some countries. The major obstacles to (formal) fish trade include an increase in domestic demand for fish, poor road infrastructure, tariff barriers, lack of quality standards and, in recent years, foreign exchange constraints. No significant quantities of fermented fishery products are exported outside Africa but there is a high demand for the products from African residents abroad.
Post-harvest handling, processing and marketing of fish are divided along gender lines but the roles change from one region to another. In the coastal countries of West Africa, women dominate the processing and marketing of fishery products. Ghanaian fishermen and women are actively engaged in the industry along the shores of West Africa. They operate in Côte d'Ivoire, the Gambia, Liberia and Sierra Leone from where they export fermented fish to Ghana. In the Sahelian zone and parts of East and Central Africa, men are also involved and, in some countries, even dominate fish processing and marketing. Fish processors and traders are not organized into formal associations or cooperatives. They operate as individual or family units and occasionally hire labour to assist in the operations.
Fermented fish is a value-added product. However, since the raw fish is derived from poor quality or underutilized species which are cheap, product prices are affordable to many low income consumers. Some types of fermented fish, processed from high-value species and considered a delicacy (e.g. guedj, koobi, fessiekh), are however expensive.
Fish consumption patterns in general and a preference for fermented products in particular depend on the prevailing food habits as well as social, cultural and economic factors in the country.
Per capita fish consumption is relatively high in the coastal countries of West Africa. Fish constitutes the main source of animal protein. In the Sahel region, meat (beef or mutton) is consumed on a large scale. However, it was noted that fish is becoming popular in these areas due to the increasing price of meat products as a result of severe droughts. The coastal countries of West Africa, Egypt, southern Sudan, Zaire and the north-western districts of Uganda are the main centres of fermented fish consumption. Depending on the degree of fermentation, fermented fishery products are used either as a condiment to enhance flavour or as food fish and a source of protein. Cured, including fermented, products contribute significantly to dietary protein requirements.
Finally, the study has revealed that fermentation is combined with salting and/or drying to salvage large quantities of fish which would otherwise have been discarded due to poor quality or as unpopular species. It can, therefore, be inferred that the physical loss of raw fish through spoilage may consequently be lower than often estimated: 20-30 percent.