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close this bookSmall-Scale Processing of Fish (ILO - WEP, 1982, 140 p.)
View the document(introduction...)
View the documentAcknowledgements
View the documentPreface
close this folderCHAPTER I. INTRODUCTION
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View the documentI. FISH SPECIES
View the documentII. PROCESSING METHODS
close this folderIII. PREVENTION OF LOSSES AND SPOILAGE OF FISH
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View the documentIII.1. Prevention of spoilage of fish before processing
View the documentIII.2. Prevention of spoilage of fish during processing
View the documentIII.3. Prevention of spoilage of fish after processing
close this folderCHAPTER II. SALTING - DRYING - FERMENTING
View the document(introduction...)
close this folderI. FISH PREPARATION
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View the documentI.1. Equipment for fish preparation
View the documentI.2. Gutting and splitting methods
close this folderII. SALTING
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View the documentII.1. Kench salting
View the documentII.2. Pickle curing
View the documentII.3. Brine salting
View the documentII.4. Salt quality
close this folderIII. DRYING
View the documentIII.1. Basic principles
View the documentIII.2. Natural drying
View the documentIII.3. Artificial drying
View the documentIII.4. Solar drying
View the documentIV. PACKAGING AND STORAGE
close this folderV. METHODS OF PREPARATION
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View the documentV.1. Dried/salted fish
View the documentV.2. Dried-unsalted fish
View the documentV.3. Dried/salted shark
View the documentVI. GENERAL PLAN FOR A FISH CURING YARD
close this folderVII. FERMENTED FISH PRODUCTS
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View the documentVII.1. Products which retain substantially the original form of the fish
View the documentVII.2. Fish paste products
View the documentVII.3. Liquid fish products
View the documentVII.4. Packaging
close this folderCHAPTER III. FISH SMOKING AND BOILING
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close this folderI. SMOKING
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View the documentI.1. Fish preparation prior to smoking
View the documentI.2. Cold smoking
View the documentI.3. Hot smoking
View the documentI.4. Fuel
View the documentI.5. Smoking kilns
View the documentI.6. Preparation of some smoked fish products
View the documentI.7. Packaging and storage of smoked fish
close this folderII. BOILED FISH PRODUCTS
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View the documentII.1. Traditional processing methods
View the documentII.2. Quality of boiled fish products
close this folderCHAPTER IV. THERMAL PROCESSING
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View the documentI. RAW MATERIALS
View the documentII. ENERGY AND MANPOWER REQUIREMENTS
close this folderIII. PROCESSING OPERATIONS
View the documentIII.1. Filling and sealing
View the documentIII.2. Sterilisation
View the documentIII.3. Cooling
View the documentIV. QUALITY CONTROL
close this folderV. POSSIBLE ALTERNATIVES TO THE USE OF METAL CANS
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View the documentV.1. Reusable container
View the documentV.2. New developments in aseptic (retortable) pouches
close this folderCHAPTER V. ALTERNATIVE TECHNOLOGIES: EVALUATION, EMPLOYMENT GENERATION AND MANPOWER TRAINING
View the document(introduction...)
View the documentI. ASSESSMENT OF COSTS
View the documentII. SALTING AND DRYING
View the documentIII. SMOKING
View the documentIV. THERMAL PROCESSING
View the documentV. EMPLOYMENT IMPACT OF ALTERNATIVE FISH PROCESSING TECHNOLOGIES
close this folderVI. ASSISTANCE TO THE SMALL-SCALE FISHERIES SECTOR: MANPOWER TRAINING AND SUPPORTING SERVICES
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View the documentVI.1. The socio-economic framework
View the documentVI.2. Infrastructural requirements
View the documentVI.3. Organisation of production and marketing of fresh and cured fish
View the documentVI.4. Extension services and training
close this folderCHAPTER VI. IMPACT OF SMALL SCALE FISH PROCESSING OPERATIONS ON THE ENVIRONMENT
View the document(introduction...)
View the documentI. FISH RESOURCES
View the documentII. WASTE DISPOSAL
View the documentIII. AIR POLLUTION
View the documentIV. CONCLUDING REMARKS ON ENVIRONMENTAL IMPACT
close this folderAPPENDICES
View the documentAPPENDIX I. Codex Codes and Standards issued by the Secretariat of the Joint FAO/WHO Food Standards Programme, FAO, Rome.
View the documentAPPENDIX II. Bibliographical references
View the documentQUESTIONNAIRE
View the documentOTHER ILO PUBLICATIONS
View the documentBACK COVER

III.1. Basic principles

During drying, water is removed from the fish by evaporation in two phases. During the first phase, only water on the surface of the fish or very close to the surface evaporates. The rate at which the fish dry depends on the surface area of the fish, the air temperature, the speed of the current of air passing over the fish and the relative humidity or wetness of the air. The drying rate during the first phase may be increased by:

- Increasing the fish surface area by splitting the fish and scoring them.

- Choosing a drying site where the air is dry and to avoid, if possible, marshy areas and places where the air has blown over water.

- Choosing a drying site where the wind is strong.

Once the surface is dry, water will evaporate at the rate at which it rises from inside the flesh to the surface of the fish. This rate slows down as the fish gets drier.

During the second phase, the drying rate is function of:

- The type of fish. For example, the rate at which water rises to the surface is slower for fatty fish.

- The thickness of the flesh.

- The temperature of the fish.

- The water content of the fish, and

- The wetness of the surrouding air.

If moisture is removed from the fish surface sufficiently quickly, the drying rate is independent of the level of humidity contained in the air. It depends only on the rate at which water reaches the surface of the fish. If drying is very fast during the early period, the surface may dry too quickly, thus producing a hard layer which will slow down the rise of the water to the surface. This is known as case hardening. When case hardening occurs, the centre of the fish could spoil even though the fish may look as if they have been well dried.

The drying rate during the second phase may be increased by:

- Reducing the thickness of the flesh by splitting and scoring the fish before drying starts, and

- Raising the temperature of the fish.