Presentation on fish processing, preservation and trasporting
FISH PRESERVATION, PROCESSING, Transporting
BY: Muhammad Laique
Submitted To: Dr. Asma Karim
∗ Fish processing(primary processing)
∗ Fish preservation methods(secondary processing)
∗In some places, more fish is caught at times than can be
∗Methods are used in keeping the surplus fish in good condition
for later consumption.
∗Again, fishermen sometimes cannot return to their villages
promptly with fresh fish they have caught, and it will be of value
to them to know how to process(primary processing) and
preserve(secondary Processing) their catch by simple means.
∗It is also necessary to transport fish to target market or
factories while it is in good quality.
∗“The term fish processing refers to the processes associated
with fish and fish products between the time fish are caught or
harvested, and the time the final product is delivered to the
∗The harvested fish should be cleaned and cooled as soon possible
due to their strong digestive juices, fish spoil very soon and if not
gutted and cleaned promptly may develop off flavor and color.
∗A sharp knife, clean cloth, plastic bags and crushed ice must be
kept ready for gutting and cleaning of fish.
∗With the help of knife, fish should be cleaned and bled.
∗Throat should be cut and gills and entrails are removed.
∗Cleaned fish first be put in plastic bags and then in ice.
∗To prevent contamination, hands, working area, cutting boards,
knives and other utensils should be properly cleaned with water
Processing Of Fish
∗ FISH PRESERVATION
∗ Preservation is the processing of food so that they can be
stored for a longer time.
∗ Preservation of fish is done to prevent spoilage.
∗ Since fish is very perishable, it is therefore, necessary to preserve
fish if not consumed or disposed immediately.
∗ Fish preservation is the method of extending the shelf life of fish
and other fishery products by applying the principles of chemistry,
engineering and other branches of science in order to improve the
quality of the products.
∗ Some of the important reasons for preserving foods are
1. To take care of the excess produce.
2. Reaches areas where the food item is not available
3. Makes transportation and storage of foods easier
4. Preserving Foods at Home
∗ Fish Foods can be preserved by the following methods-
∗ (i) Salting
∗ (ii) Dehydration
∗ (ii) Increasing temperature(Smoking)
∗ (iii) Lowering temperature(chilling and freezing)
∗ (iv) Using preservatives(Canning and pickling)
∗ METHODS OF FISH PRESERVATION
∗ a. Salting
∗ Salt is the preservative agent used to lengthen the
shelf life of fish and fishery products as it absorbs
moisture from organism and drastically reduce
∗ This is used in almost all methods of preservation
except in icing, refrigeration and freezing.
∗ There many different kinds of salt, some being better
than others for fish curing.
∗ A distinction must be made between the two chief
techniques of salting:
Wet Salting:Wet Salting:
∗ This is the cheaper, since it requires lesser amounts of
∗The principle is to keep the fish for a long time in brine.
∗The equipment needed consists of a watertight
∗container, which can be a tin, drum, barrel, etc.
∗To make the brine, one takes four parts of clean water
(sea or fresh water) and one part of salt.
∗If the salt is coarse, it has to be ground or pounded first.
∗It is then dissolved into the water by stirring with a piece
∗To be good, the brine must float a fish.
∗ The next step depends on what kind of fish one
wants to salt.
∗ It is best first to cut off the head and gut, and clean
the fish, though small fish can also be salted whole.
∗ Large fish must be cut open, and it is preferable to
take out the backbone.
∗ Fish with heavy armour of scales must be scaled.
∗ In places where the flesh is thick, slashes must be
made so that the salted brine can penetrate the flesh.
Dry SaltingDry Salting::
∗ In this method the fish is salted but the juices, slime
and brine are allowed to flow away.
∗Dry salting can be done in an old canoe, or on mats,
leaves, boxes, etc.
∗In any case, the brine formed by the fish juices and the
salt must be allowed to run away.
∗For two parts of fish, one needs one part of salt.
∗Layers of fish must be separated by layers of salt.
∗It is a valuable method when one has no containers.
∗ SUN DRYING AND DEHYDRATION
∗ Drying is the process in which moisture is removed by
exposure to natural air current as humidity is
regulated by climatic condition.
∗ Dehydration is the process of removing moisture with
the use of mechanical device that provides artificial
heat for drying.
∗ Very small and thin fish can be dried straight away in
the sun if they are brought in early enough in the
morning (and if, of course, the sun is shining!).
∗ If these conditions are not fulfilled the fish must be
put for one night in brine, or dry salted.
∗ They can then be dried the next morning.
∗ Any kind of fish can be smoked. There are three main methods
∗ (a) cold Smoking;
∗ (b) Hot smoking;
∗ (c) Long smoking.
∗ Cold Smoking:
∗ Cold smoking is exactly what it sounds like. Cold-smoked
∗ fish are not cooked, because the temperature generally does
not exceed 43° C. Cold smoking is customarily performed
below 30° C to prevent undesired changes in the muscle
texture. To maintain the proper temperature, ensure uniform
drying and preserve the desired colour, it is necessary to use
an indirect source of heat and smoke.
∗ The cold-smoking process is primarily used for salmon.
∗ Other traditional cold smoked items include black cod
(sablefish),trout, eel, herring, haddock and cod.
∗ Hot Smoking: The hot smoking system can be used for
immediate consumption or to keep the fish for a maximum of
48 hours. Small fish can be salted first for half an hour .
∗ After salting they are put on iron spits and dried in a windy
place or in the sun for another half hour, and then hot smoked.
∗ The fish will be ready in about one hour. An indication that they are done
will be found in the golden yellow colour of the skin.
∗ Hot-smoked fish are moist and juicy when properly finished. Because of
this, they have a relatively short shelf life and must be refrigerated.
∗ Long Smoking: If fish must be kept in good condition
for a long time, for instance, two or three months or
even longer, it can be done by smoking, provided the
fish is not oily.
∗ For this purpose, a small closed shed made of palm
leaves or other local material can be used.
∗ The dimensions of the shed depend, of course, on the
quantities of fish to be smoked, but the height should
in no case be less than six feet.
∗ In this shed, racks are built to hang the fish from or to
lay them upon.
∗ Hanging the fish on spits is the best method, but they
can also be laid on loosely-woven matting.
∗ One can start hanging fish three feet from the
bottom up to the roof.
∗ This is obtained by covering the fish with layers of ice.
∗ However, ice alone is not effective for long preservation .
∗ Because melting water brings about a sort of leaching of
valuable flesh contents.
∗ Which are responsible for the flavor.
∗ But ice is effective for short term preservation such as is
needed to transport landed fish to nearby markets or to
canning factories etc.,
∗ This is more effective than chilling.
∗ Freezing is achieved either by using a mixture of ice
and salt or refrigeration.
∗ The sub zero temp so obtained keeps the fish frozen
∗ To prevent rancidity, the frozen fish is subject to
glazing with water or it is wrapped in a cover of
moisture proof wax paper.
∗ Glazing is dipping the frozen fish in water so that
finally a layer of hard ice surrounds the fish.
∗ This layer affords protection against exposure of fish
fat to atmospheric oxygen, thus preventing rancidity.
∗ This is a very effective method though costly.
∗ Product is very god and retains much of flavor.
∗ Fish is cleaned and then cut to proper boneless pieces
in filleting plants.
∗ The pieces are then brined or pickled to improve
∗ Preliminary cooking is then carried out.
∗ Cooked pieces are then put in cans.
∗ Final cooking combines sterilization with steam and
high temperature at 110celsius.
∗ The cans are finally sealed in canneries.
∗ Keeping period depends upon the quality of raw
material used as well as the vacuum created in the
∗ Pickling is an easy method of preserving fish. Pickled fish must be
stored in the refrigerator at no higher than 40° F (refrigerator
temperature), and for best flavor must be used within four to six
∗ Only a few species of fish are preserved commercially by pickling,
but almost any type of fish may be pickled at home.
∗ Refrigerate the fish during all stages of the pickling process.
∗ Transportation of fish and fish products
∗ Development in fish preservation and transportation has
increased significantly the share of fish production that enters
international trade. Fish is traded live, fresh, frozen, cured or
canned. It is transported by sea, air or land. Live, fresh and
frozen fish require special care in comparison with cured or
∗ Important ways of transporting fish are :
∗ Through air
∗ Through land
∗ Through sea(ships)
∗ Through Boats
∗ Live fish
∗ Transportation of live fish requires oxygen for respiration and
removal of the toxic gases and by-products that accumulate,
such as CO2 and ammonia. Certain fish, like catfish, can obtain
oxygen through the damp surface of their gills or through the
body skin. Other fish, like the climbing perch, have accessory
air-breathing organs. But most finfish are transported live in
water supersaturated with oxygen and kept at a temperature
low enough to reduce their metabolism. Some tropical fish
may not support temperatures below 10°C.
∗ Fish is often starved (also called conditioned) before
transportation to reduce its metabolism and increase the
packing density. Crustaceans are transported live in wet
packages using wet sawdust or other ways to keep the
atmosphere surrounding the live animals humid and cool.
∗ Quality and Quantity of Fish
∗ pH, Carbon Dioxide and Ammonia
∗ Biochemical Changes and Stress in Transported Fish
THE MAIN FACTORS AND PRINCIPLES
ASSOCIATEDWITH FISH TRANSPORT
∗ The quality of fish transported is a decisive criterion. The fish
to be transported must be healthy and in good condition.
Weakened individuals should be eliminated from the
consignment, particularly when the temperature during
shipment is high. When the fish are of poor quality, even a
great reduction of fish density in the transport container
fails to prevent fish losses. Weak fish are killed at a much
higher rate than fish in good condition when the transport
time is longer.
Quality of Fish
∗ The most important single factor in transporting fish is providing an adequate
level of dissolved oxygen. The ability of fish to use oxygen depends on their
tolerance to stress, water temperature, pH, and concentrations of carbon
dioxide and metabolic products such as ammonia.
∗ Heavier fish and those transported in warmer water need more oxygen. For
instance, if the water temperature increases by 10°C (e.g., from 10 to 20°C),
∗ Some conversion coefficients of oxygen demand are indicated by the FRG
Fish type Oxygen Demand
NOTE: Taking the oxygen demand of
carp as 1
∗ The source of the water used during transport must have been tested before
dispatching a mass consignment of fish. The water pH level is a control factor
because the proportions of toxic ammonia and CO2 contents are direct
functions of pH.
∗ With increasing transport time, CO2 production through fish respiration shifts
water pH towards acidity. Water pH levels about 7–8 are considered as
optimum. Rapid changes in pH stress fish, but buffers can be used to stabilize
the water pH during fish transport. The organic buffer
trishydroxylmethylaminomethane is quite effective in fresh and salt water.
∗ Ammonia (NH3) builds up in transport water due to protein metabolism of the
fish and bacterial action on the waste. Decreasing metabolic rate of the fish
by lowering the water temperature, and thus lessening fish activity, reduces
the production of NH3.
pH, Carbon Dioxide andpH, Carbon Dioxide and
∗ Shipment conditions also influence the composition
of fish blood and the parameters of blood serum
biochemistry. Increased temperature and a lower fish
weight-to-water concentration ratio mean a higher
number of erythrocytes and a greater haemoglobin
concentration of fish blood. No such changes occur at
lower temperatures and a lower fish proportion in
relation to water volume
Biochemical Changes and StressBiochemical Changes and Stress
in Transported Fishin Transported Fish
∗ A fish transport tank wagon (Vollmann-Schipper, 1975) M -
technical space and attendant's booth, U - pump and air
compressor, T - Transport tanks 1 and 2, S - oxygen cylinders, A
-tank drain, F - water aeration (for details see Fig. 50), L - loading
space, W - circulating water distribution system, S + D - oxygen or
compressed-air distribution system
∗ Use of Fish Tranquilizers
∗ Application of Sodium Chloride and Calcium Chloride
∗ Chemicals as Oxygen Sources (K2S2O8, Na2S2O8,
∗ Bacteriostatic Chemicals
∗ Ammonia Control
∗ Antifoam Chemicals
CHEMICAL METHODS FOR WATER AND FISH
TREATMENT DURING TRANSPORT