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close this bookSmall-Scale Processing of Fish (ILO - WEP, 1982, 140 p.)
close this folderCHAPTER I. INTRODUCTION
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View the documentI. FISH SPECIES
Open this folder and view contentsIII. PREVENTION OF LOSSES AND SPOILAGE OF FISH


This section briefly reviews processing methods which will be described in greater detail in subsequent chapters. These methods do not include technologies which are more appropriate for capital-intensive medium and large-scale processing plants.

II.1. Salting

During slating, the flesh of the fish looses some of its water and is impregnated with salt. Rapid penetration of salt into the flesh is desirable for good protection of the product during the curing process. Salting can be done by a number of methods. The obtained results are influenced by such factors as climate, salt quality, type and quality of the fish used, the type of product desired by consumers and cost. Fish may be slated by rubbing dry salt into the flesh or by immersing the fish in a brine (a solution of salt in water). The juices extracted from the fish during dry salting can be allowed to drain away (Kench curing) or they can be contained in order to keep the fish covered by a salty liquid or “pickle” (pickle curing).

II.2. Drying

Simple drying in the sun is one of the commonest methods of curing used in tropical countries. Natural drying using the action of sun and wind constitutes one of the least expensive drying methods. Furthermore, the type of packaging used for dried fish is also fairly inexpensive. Altogether, dried fish is particularly suited for low-income groups which cannot afford expensive fish products. Simple improvements, such as the use of drying racks raised above ground level can increase drying rates and reduce contamination, thus helping to make products of good quality.

Mechanical dryers are relatively expensive to buy and operate. Although the output may be of better quality than that produced by natural drying, artificially dried fish will, most probably, be too expensive for the majority of low-income consumers.

II.3. Smoking

During smoking, the heat from the fire dries the fish while chemicals from the smoke impregnate the flesh. The obtained flavours depend both on the raw materials used and the length of time the fish are smoked.

There are many traditional smoking methods: these range from simple open fires or smoke pits to smokehouses covering a considerable area. Structures used in traditional smoking methods can be built with local materials and labour. They have however a major disadvantage: most of these structures are wasteful of fuel, usually firewood, which has become both scarce and expensive in some countries. A number of modified and improved designs have been produced in order to partially overcome the above disadvantage. The modified structures are easier to use than the traditional pits, and produce smoked fish of a more even quality, using less fuel.

Smoking is one of the most common curing process wherever salt is in short supply, most notably in the inland fisheries of Africa.

II.4. Other curing methods

Brine preserved, pickled and fermented fish products such as fish pastes and sauces are widely made in South-East Asia but not elsewhere in the tropics. Spoilage is prevented in these cures by the addition of large quantities of salt. A fish paste is obtained whenever a moderate amount of breakdown of protein occurs. If the breakdown is permitted to continue further, a liquid sauce is obtained. All these products contain large quantities of salt, and can there fore be eaten only in small quantities at one meal.

Boiled fish products are also of considerable importance in South-East Asia. Some products are simply boiled; they can then be kept for only a few days at tropical temperatures. Sometimes, the boiled fish is dried and the products can then be kept for many months. A few products are made by boiling and salting in sealed containers, yielding cured fish with a relatively long storage life.