III.1. Prevention of spoilage of fish before processing

A great deal of spoilage may occur before the fish is processed. The bacterial and chemical changes which cause spoilage proceed rapidly at the temperature at which tropical fish normally live (in the range of 25-30°C). In general, the lower the temperature of the fish, the slower the change which causes spoilage. Furthermore, spoilage may be reduced if fish are handled properly, and good hygienic measures are adopted. A few measures for avoiding or minimising spoilage are briefly described below.

(i) Improvement of landing facilities and distribution. Very often, whenever unexpectedly large catches are taken, landing facilities and the distribution system cannot handle the surplus of fish. Thus, a long period of time may elapse before the fish can be processed. Consequently, a high percentage of the fish may become unsuitable for processing. It is therefore important to expand cold storage facilities in proximity of the catch areas whenever sufficient and/or adequate transport facilities (e.g. trucks equipped with a refrigeration system) are not available. Alternatively, processing plants may be located near the catch areas in order to avoid the need for extensive transport facilities.

(ii) Maintaining the fish at low temperatures. To minimise spoilage, fish should be kept as cool as possible immediately after catching until processing starts. If tropical fish are chilled with ice, they may be kept in an edible condition for an increased period. The actual length of time depends very much on the type of fish, but may be as long as three weeks. However, in many areas far away from major towns, ice may not be available in sufficient quantities. Fish may then be kept relatively cool by other means, including the following:

- keeping the fish in the shade out of direct sun,

- placing damp sacking over the fish. This helps reduce the temperature as the water evaporates. The sacking must be kept wet and the fish must be well ventilated.

- mixing the fish with wet grass or water weeds in an open-sided box so that the water can evaporate and cool the fish. In this method, the fish should be kept continuously wet.

(iii) Maintaining a hygienic environment. Fish which have been handled cleanly and carefully will be in a better condition than fish which have been handled carelessly; they can, therefore, be worth more money.

Before processing starts, attention to the following points is important.

- To keep the fish as clean as possible. Washing with clean water will remove any of the bacteria present on the fish skin, especially in the presence of mud.

- To keep the fish cool, chilled in ice or chilled water, if possible, at all stages before processing starts. Fish spoilage is a continuing process: once a particular stage of spoilage has been reached no amount of good practice or processing can reverse it.

- To avoid damaging fish by careless handling. If the skin is broken this will allow bacteria to enter the flesh more quickly and spoilage will be more rapid. This sort of damage can be caused by walking on fish and by the use of a shovel. If the guts can be removed and the gut cavity washed carefully, this will reduce the number of spoilage bacteria present; however, in some areas, the purchaser requires whole fish so that this practice may lower the value of the catch.