Freezing Method Of Preservation

Presented By:- “Pakhtoon
Group”
Sumitted To:- “Prof.Punhal
Khan Lashari”
Department Of Freshwater
Biology & Fisheries,
University Of Sindh Jamshoro.

Our topic is Which is the Method
of Preservation.
Now the question arises, That what is
preservation?
* Preservation is the processing of food so
that they can be stored for a longer time.
* Preserved food is not healthy as fresh
food because it decreases the nutrition
value of food.

There are ancient methods of
preserving fish included
&
All of these techniques are still
used today but the more modern
techniques of and
have taken on a large
importance.

* Freezing is a process of preservation in which the
temperature of fish & fishery product is learned at
-40 centigrade or below with most of the water inside
of tissue turning into ice.
* Freezing means removal of heat from the body.
* Freezing, or solidification, is a transition phase in
which a liquid turns into a solid when its
temperature is lowered below its freezing point.

(Frozen Fish)
=>Freezing fish is the simplest and the most natural way of
preserving fish. Freezing is very easy and safe to do. The
following are the simple steps to follow in freezing fish.

Step 1: Select fresh fish for freezing.

*Step 2: If the fish are small like dilis, wash and
freeze right away.

& If fish are large like bangus, remove scales,
entrails, trim fins, tail & then wash.

Step 3: Wrap fish in Plastic wrap or put in container
packed tightly to eliminator air.

Step 4: Label wrapped fish or container with
name and date.

Step 5: Freeze immediately
• This is more effective method than chilling.
• Freezing is achieved either by using a mixture of
ice and salt or refrigeration.

The temperature is usually -25 centigrade or
lower but may vary from -15 Centigrade to -29
Centigrade & freezing may take 3 to 72 hours.
This is a sudden decrease in the temperature of
fish upto freezing.
The temperature usually -40 Centigrade &
freezing
time is 30 min to 1 hour.

Cold air is circulated by Fans over an evaporatotr.

Freezing by placing the Products in direct contact or
plate freezers.

Direct contact between a cold liquid, or gas from that
liquid and the fish.

Washing Descaling
Removal
Of Gut
Removal
of head
Removal
of fins
Store in
the freezer

1: The temperature falls fairly rapidly, at a more or
less constant rate, to just below 0 Centigrade while the
specific heat being remove.
2: The temperature remains fairly constant at about -1
Centigrade to -5 Centigrade while the latent heat is
being removed and the liquid water is Changing to ice;
This is known as Thermal Arrest Period (TAP).
3: The temperature drops rapidly again while the
specific heat of ice is being removed and most of the
remaining water freezes.

• To slow down fish spoilage.

* To increase the shelf life of
fish.
* To prevent the microbial
growth.
* To prevent the bacterial
activity.

=> Desiccation starts from the surface of
the body.
=> Discolouration occurs due to
breakdown of haemoglobin.
=> Toughness of muscles increases.
=> Proteins inversibly dehydrated

• Freezing and storing at an ambient
temperature of -4F (-20 Centigrade) or below
for 7 days.
• Brinning & pickling may reduce the
parasite hazard in fish.
• Should maintain hygenice condition
during freezing for avoiding contamination.

Freezing Method Of Preservation

Freezing Method Of Preservation

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