SE Johnson and IJ Clucas
This booklet describes how insulated fish boxes can be easily constructed from cheap, locally available materials.
There are various methods of storing fish in containers, both at sea and on shore. However, fish are often damaged. Boxes protect the fish during transport and enable the fisherman or seller to ice the fish efficiently. This means that a good quality product arrives in the market. Fish boxes make handling easier and allow for sorting by size or species.
Boxes must be a suitable size for the fish
The fish must be able to fit into the box without bending or hanging over the sides. A range of box sizes may be needed.
Type of fish will effect the depth of the box
The recommended maximum depth for a box for white fish is 600 mm, for fatty fish 400 mm and for fillets 200 mm.
Boxes should be easily sleeked
When securely stacked the weight of the upper box should be supported by the box underneath and not by the fish inside it.
Boxes should be small enough to be easily lifted when full If the box is used for transport, it should be lifted easily by one person (up to 30 kg) or two people (up to 50 kg), or be designed to be lifted by machinery.
They should be easy to clean Boxes must have a surface which does not hold dirt and should be easy to clean with detergent and disinfectant. The material should be waterproof and should not absorb smells.
There should be drainage for meltwater Holes in the sides should allow drainage of meltwater away from the boxes stacked underneath. A false bottom to raise the fish above the collected water can also be used.
These basic points apply to the construction of all types of fish boxes.
The material from which the box is made can effect the quality of the fish.
Materials such as wood, bamboo, cane and reeds are all absorbent and soak up dirty water in which bacteria can grow and spoil the fish. They are also difficult to clean, even when using detergents and chlorine disinfectants, and become heavy when they are waterlogged.
If wood is the only material available for making the boxes, it is possible to reduce absorption of water and dirt by either coating the wood with plastic or lining the box completely with a plastic sheet. These also help the box to last longer.
Plastic boxes are better because they are non-absorbent and durable. They are also easy to clean, light to handle and easy to stack. Various types of plastic can be used, depending on how strong or heat resistant they need to be.
There are two disadvantages with plastic boxes.
1) They are more expensive than wooden boxes.
2) They can be used for other purposes and may not always be returned.
Insulated fish boxes In tropical climates ice melts quickly. To ensure that good quality fish arrives at the market, it must be iced. Insulation slows melting, so reduces the amount of ice needed. This saves money. Uninsulated fish boxes may be used where other insulation is provided, for example, in an insulated fish hold or truck. Otherwise insulation of the fish boxes is needed. To work efficiently the boxes must be completely insulated using a suitable material and be provided with drainage to separate the fish from the meltwater.
Materials suitable for insulation
To make these boxes, insulating material is packed between two layers of strong, waterproof, non-absorbent boarding. Suitable materials for the insulating layer include cork, glassfibre, expanded polystyrene and polyurethane foam, although kapok or sawdust may be used.
Heat should not pass through the insulating material which should also be waterproof. There should be a waterproof layer between the fish and the inside of the box.
Granular insulators, such as sawdust, tend to settle and this reduces their insulating effect. Materials like kapok, when compressed, also lose their power. Any material used should be resistant to rodent or fungal attack and non-toxic.
Types of insulated fish boxes
The exact design of fish box chosen depends where it will be used. The points already discussed should always be considered. The thickness of the insulating layer is related to the intended use.
If an insulated container cannot be used, the use of cheap materials, e.g. newspaper, woven palm leaves, banana leaves, sawdust, to wrap the box in can be considered. Fresh materials are needed each time the box is used.
This box has a fibre reinforced plastic inner and outer lining (3 mm thick), laminated directly on to 70 mm thick polyurethane foam. An insulated lid drops into a hole at one end of the box. A drainage hole is fitted at a bottom corner and removable wooden divider boards are provided.
This box has a wooden outer layer (20 mm), a 80 mm layer of tarred expanded polystyrene, and an inner (0.5 mm) layer of aluminium sheet. A rubber ring is fitted around the lid to ensure a good seal. The id is hinged on one side and secured by locks on the other. A drainage hole is included.
If fish boxes are used at all stages of fish handling, at sea, during transport and at retail sale outlets, the fish are protected from physical damage and the use of ice is made easier. Plastic boxes, though expensive, are the most useful as they are long lasting, easy to clean and non-absorbent.
If there is no insulation in the hold or transport, insulated boxes should be used. These are more expensive than uninsulated fish boxes but less ice melts during storage.
Clucas, I.J. and Whitehead, W.D.J. (1986) The design and construction of fish boxes from locally available materials in developing countries. TDRI Report No. G192.
Kamari, A. and Sayers, J.A.C. (1979) The Use of Standard Returnable Fish Containers in ASEAN Countries. ASEAN-Australian Economic Cooperation Food Handling Project. ASEAN Food Handling Bureau, Malaysia.
For further information contact
Natural Resources Institute
Kent ME4 4TB
Tel: 0634 880088
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