Fish is an extremely perishable food item.
Owing to the high perishability of fish and fishery products, 90
percent of trade in fish and fishery products in quantity terms (live
weight equivalent) consists of processed products. Fish are increasingly
traded as frozen food (39 percent of the total quantity in 2010,
compared with 25 percent in 1980). In the last four decades, prepared
and preserved fish have nearly doubled their share in total quantity,
going from 9 percent in 1980 to 16 percent in 2010. However, trade in
live, fresh and chilled fish represented 10 percent of world fish trade
in 2010, up from 7 percent in 1980, reflecting improved logistics and
increased demand for unprocessed fish
1. In high ambient temperature of the tropics like Nigeria, fish will
spoil within 12-20 hours depending on species, methods of captures etc.
2.
In the healthy live fish, all the complex biochemical reactions are
balanced and the fish flesh is sterile. After death however,
irreversible change that results in fish spoilage begins to occur. The
resultant effect is the decomposition of the fish.
3. The processing and preservation of fresh fish were of utmost importance
since fish is highly susceptible to deterioration immediately after
harvest and to prevent economic loss.
4. This spoilage can be reduced or temporarily halted by various techniques.
Some of the aspects of fish processing include
1. Fish Canning-
Canning is a modern technological advancement in food processing which
improves the shelf life of the fish enabling its storage for several
years. The canning process involves hermetically sealing the product in a
container, heat sterilizing the sealed product and cooling to room
temperature for storage. An example is the popular sardine.
2. Mince Fish-
Mince fish are fish flesh separated from the skin and bones. Separating
methods may be mechanical using deboning machines or combined chemical
and physical methods. The separated flesh could be processed into
delicate fish products such as fish fingers, fishcakes, fish sausages
which is sold frozen or part filled in oil.
3. Fish Silage-Fish
silage or liquefied fish protein is a mixture of fish liquid by enzymes
in the presence of an acid. This simple technology of processing fish
or fish waste into silage is scarcely utilized in developing countries,
because acids have to be imported. The raw material for silage
production can be provided locally from the following:
· Catches from another fishery
· artisan seasonal glut
· Products of fish processes.
This serves as an excellent livestock feed.
4. Fish Meal-The
production of fishmeal and oil is the predominant method of processing
the world’s supply of non-edible fish and fish frames from filleting
operations with the oil used in the leather, soap and pharmaceutical
industries, and the residue as a source of quality fertilizer and
livestock feed. This is achieved using the wet process or dry process.
5. Other processing and
storage mechanism include drying, smoking, salting, roasting, frying,
cooking, chilling and freezing among others.
STEPS INVOVE IN FISH PROCESSING
Fish processing is a value addition process which involve several
precautions to ensure Food safety. Several requiements have been put in
place to ensure processing facilities meet up with internationaly
accepted practises of food safety.
PRE PROCESS OPERATIONS
There are many types of fish products available to the consumer but
most of them will have undergone some sort of initial preparation before
processing. This preparation can be in the form of stunning of fish,
grading, removal of slime and cutting the fish in a particular way to
produce the raw material necessary for future processing. Due to the
delicate nature of the fish and the rapid rate of deterioration that can
occur if the fish is treated badly, it is extremely important to handle
it hygienically and carefully during all stages of preparation.
Stunning of fish
Stunning of freshly caught fish or fish delivered live to a
processing plant is best done with an electric current. First, the fish
are placed in a tank of water and an electric current is then passed
through the water to stun or kill the fish. Live fish are also
slaughtered by cutting the aorta and bleeding to death. In some plants,
water in the fish tank is saturated with carbon dioxide or salt, which
renders the animals unconscious or dead.
Grading of fish
Sorting by species or on the basis of freshness and physical damage
are still manual processes, but grading of fish by size is easily done
with mechanical equipment. Size grading is very important for fish
processing (i.e., smoking, freezing, heat treatment, salting etc.) as
well as for marketing.
Removal of slime
Slime accumulating
on the skin of dying fish is a protection mechanism against harmful
conditions. In some fish species slimes constitutes 2-3% of body weight.
Slime creates a perfect environment for microorganism growth and should
be removed by thorough washing. Soaking fish in a 2% solution of baking
soda and then washing in a cylindrical rotating washer can remove slime
from freshwater species.
Splitting, gutting and filleting.
There are several reasons why we cut and gut fish.
1. To add value to the product (e.g. making fillets);
2. To make the product acceptable to the customer;
3. To maintain the quality by reducing spoilage;
4. To make further processing easier;
5 To reduce processing costs;
6. To improve storage life; and
7. To reduce transport costs/charges.
Splitting
Splitting or opening the fish is usually done if the fish is to be
salted, dried or smoked. It increase the cut surface area that is
exposed to the air and decreases the thickness of he fish, so drying is
faster,
Cutting and Gutting
Cutting and gutting is done to help reduce spoilage, as guts are full
of bacteria and enzymes, and are not usually eaten. Making a ventral
cut from the gill to the anus, pull out the guts with the fingers and
thoroughly wash out the cavity.
These processes generally take place within separate areas of the
fish processing plant. The fish are kept on ice in boxes before being
delivered to the fish processing plant until required for further
processing.
This can be processed into fillet or smoked.
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