Refrigeration and freezing play vital roles in the fish industry, ensuring the preservation of fish products while maintaining their quality and extending their shelf life. As highly perishable commodities, fish and seafood require immediate cooling and storage at low temperatures to inhibit bacterial growth and enzymatic reactions that lead to spoilage. With the global demand for fish products on the rise, efficient refrigeration and freezing techniques have become essential in the fish industry to meet consumer expectations for fresh and safe seafood.

1. Refrigeration & Freezing

2. Refrigeration and freezing play vital roles in the fish industry, ensuring the
preservation of fish products while maintaining their quality and extending
their shelf life.
As highly perishable commodities, fish and seafood require immediate
cooling and storage at low temperatures to inhibit bacterial growth and
enzymatic reactions that lead to spoilage.
With the global demand for fish products on the rise, efficient refrigeration
and freezing techniques have become essential in the fish industry to meet
consumer expectations for fresh and safe seafood.
Introduction

3. Refrigeration & Freezing
Freezing
Freezing is a phase transition where a liquid turns into a solid when its
temperature is lowered below its freezing point.
Freezing preserves the storage life of foods by making them more inert and
slowing down the detrimental reactions that promote food spoilage and
limit quality shelf life.
Refrigeration
The term refrigeration denotes cooling of a space, substance or system to
lower and/or maintain its temperature below the ambient one while the
removed heat is rejected at a higher temperature.
Refrigeration is considered an artificial, or human-made, cooling method

4. Advantages:
 Freezing reduces the number
of potentially harmful bacteria
that can cause food poisoning
 Freezing minimize the loss of
quality of a products & flesh is
changed very little
 Keeps for long as we want to
keep when supply is scarce
 Good quality fish can be
transported under refrigerated
conditions over long distances
Disadvantages:
 If fish is not stored correctly
in a freezer, the taste,
texture, and color can all
become compromised
 Customers often have less
interest for frozen fish
 It’s costly method
Advantage & Disadvantage of Freezing

5.  Crystallization
When a product freeze, the ice crystal formed may considerably impact the
cellular integrity, resulting in loss and degradation of food quality. The
formation of large ice crystals and uneven distribution in food ,tissue can
rupture the cellular structure.
 Re-crystallization
Recrystallization of ice crystals causes deterioration during storage and
distribution in frozen foods.
 Volume change
The principal physical changes are ice crystal formation and desiccation or
drying out of the flesh.
Technological Problems Associated with Refrigeration and
Freezing

6.  Super cooling
Super cooling is the method of lowering the temperature of a foodstuff
below its freezing point without becoming solid
 Desiccation
Freeze desiccation of foods is based on the use of a solid desiccant for the
adsorption of water vapor which sublimes from the frozen food at a reduced
pressure. The surface of this fish becomes chalky white, yellow, or brown,
with wrinkles.
Technological Problems Associated with Refrigeration and
Freezing

7.  Gaping of Fillets
Fillets sometimes gape when they are taken from fish that have been
stowed in ice, particularly when the fish are rather stale, but the problem is
more serious when whole fish are frozen
 Discoloration
Fish is rich in proteins and lipid, specially PUFA which made them vulnerable
to chemical and microbial changes. Color of flesh governed by various
pigment such as Hb, Mb, and so on.
 Protein Denaturation
When a protein is frozen, the water molecules in the protein matrix can
form ice crystals. These ice crystals can cause physical damage to the
protein structure, leading to denaturation
Biochemical Problems Associated with Refrigeration and
Freezing

8.  Change in Fat
Fat content of fish varies depending on species, sex , size , maturity etc. Lipid in frozen
fish is more likely to go rancid than lipid in other tissue.
 Toughness
The main effect of freezing and frozen storage on the quality of fish is a change in
texture of the proteins in the muscle. The tissues become tough because of the
denaturation of the proteins.
 Glycolysis
After death, glycogen of fish body is converted into lactic acid resulting in lower the pH
level. The glycogen content in fish body may gradually be fall because the methods for
fishing often lead to its exhaustion in the fish before death.
 Drip loss
When the frozen food is thawed, the water produced by the melting of ice crystals can't
be completely absorbed by the tissues and returns to its original state before freezing.
Biochemical Problems Associated with Refrigeration and
Freezing

9. Quality Aspects of Frozen Products
Quality aspects of frozen Products depends on muscle integrity, proteins, and
lipids
Due to denaturation, coagulation, reduction of protein digestibility, rancidity,
and loss of vitamins during frozen storage, quality of frozen stored fish could be
lost
Several changes are found in the fish body and muscle during the freezing and
frozen storage of fish.
These changes are, however, influenced by the temperature of the medium,
packaging and glazing of the products and relative humidity of the stores.

10. Physical Changes
 Crystallization of water in tissue increases the volume about 8-10% of the raw
fish;
 Desiccation starts from the surface of the body;
 Discoloration occurs due to break down of hemoglobin;
 Toughness of muscle increases;
 Rigidity increases as it becomes hard;
 Loses weight;
 Freeze-burn occurs;
 Trimming loss in association with the loss of nutrients occur;
 Thaw-drip or water drip occurs when frozen fish are thawed slowly;
 Slow freezing produces big ice crystals that ruptures the cell wall and causes
physical damage

11. Chemical Changes
Oxygen contact in frozen foods causes oxidative rancidity. Freezing leads to a
concentration of solutes, which dehydrate cell membranes, exposing them to oxidation
Proteins irreversibly dehydrated
Myoglobin oxidized
The destruction of ascorbic acid (vitamin C) does occur during freezing. The main
contributor to the loss of vitamins is oxidation
The disruption of plant and animal tissues through freezing leads to the release of
enzymes. At around 32°F, the enzymatic breakdown of protein is the main cause of
product quality loss
Color changes occurs in most frozen products due to changes in natural pigment in
tissues. The process of freezing will also affect the flavor and aroma of frozen foods

12. Storage Life
 Stability of a product
during storage
 Maximum time
during which it can
be kept without
undergoing change
The International
Institute of Refrigeration
recommends storage
temperature of for
 lean fish -18°C
 fatty fish -24°C

13. Products Storage life, Months
-18°C -25°C -30°
Fatty fish, sardines, salmon, ocean perch 4 8 12
Lean fish, cod, haddock 8 18 24
Flat fish, flounder, plaice, sole 9 18 24
Lobster, crabs 6 12 15
Shrimp 6 12 12
Storage Life of Different Frozen Products

14. Factors Limiting Storage Life
Temperature Type of fish Packaging
Freezer burn Time

15. .
Manufacturing of Ice And Design of Ideal Freezing Plant
Icing
Ice is used to remove heat from the fish. Without ice, or another way
of preserving the catch, fish will spoil and become inedible after 7-8
hours storage at tropical temperatures
Type of Icing-
 Flake Ice
 Block Ice
 Tube Ice
 Plate ice

16. Figure 01: Flake ice
Type of Ices
1. Flake Ice:
Flake ice is made by freezing water on the
surface of a drum and scraping it off in thin
flakes.
Advantages
 Easy to handle
 Good surface contact
 Quick cooling
 Can cover large quantity of fish
Disadvantages
 High operating cost
 Melts quickly than block ice

17. Figure 02: Block Ice
2. Block Ice:
Block ice is made by freezing water in large
containers. Large block of ice is crushed
into smaller pieces.
Advantages
 Slow melting
 Low energy consumption
 lower operating costs
Disadvantages
 Poor surface contact
 Difficult to handle
Type of Ices

18. Figure 03: Tube Ice
3. Tube Ice:
Ice is formed on the inner surface of the vertical
tubes and is produced in the form of small
hollow cylinders.
Advantages:
 Excellent media for chilling
 No physical damage to fish occurs
 Can cover large quantity of fish for a given
weight compared to crushed block ice.
Disadvantages:
 It is costly
 Melts quickly than block ice.
Type of Ices

19. Figure 04: Plate ice
Type of Ices
4. Plate ice:
Water is sprayed and frozen onto the outer surface
of vertical hollow plates through which the
refrigerant passes. Water will freeze on the plates
as flat sheet of ice.
Advantages:
 Excellent media for chilling
 No physical damage to fish occurs
 Can cover large quantity of fish for a given
weight compared to crushed block ice.
Disadvantages:
 It is costly
 Melts quickly than block ice.

20. 1. Jacketed Cold Store:
A jacketed cold store is a type of cold storage
facility where the walls, ceiling, and floor of the
storage room are constructed with double layers.
Figure 05: Jacketed cold store
2. Gridded Cold Store:
A gridded cold store, also known as a modular or
panel cold store, is a cold storage facility
constructed using prefabricated insulated panels.
Figure 06: gridded cold store
Types of Cold Store

21. 3. Finned Cold Store:
A finned cold store is a cold storage facility
where the refrigeration system includes
finned evaporator coils mounted on the
walls or ceiling of the storage space.
Figure 07: Finned cold store
4. Unit Cooler
A unit cooler is a refrigeration system component
that consists of a coil and a fan. It is commonly
used in cold storage facilities to cool the air and
maintain the desired temperature.
Figure 08: Unit cooler cold store

22.  Design of an Ideal Freezing Plant:
According to Graham, (1984) and Ashok,
(2021) the design of an ideal freezing plant
involves several key considerations to
ensure efficient and effective freezing of
perishable goods, including fish.
 Layout and Workflow
 Freezing Equipment
 Temperature Control
 Air Circulation and Ventilation
 Insulation
 Hygiene and Sanitation
 Automation and Controls
 Energy Efficiency
 Safety and Emergency Preparedness
 Compliance with Regulations
Figure 09: Layout of an ideal freezing plant (Source:
Graham, 1984)

23. Design of an Ideal Cold Storage:
The design of an ideal cold storage room is
crucial for maintaining the quality and
freshness of perishable goods, including
fish (Shaheed et al., 2016). Here are some
key considerations and features to focus
on when designing a cold storage room:
 Size and Layout
 Insulation and Construction
 Temperature Maintenance
 Air Circulation and Ventilation
 Floors
 Lighting
 Hygiene and Sanitation
 Security and Access Control
 Emergency Preparedness.
 Suspended ceilings
 Compliance with Regulations
Figure 10: Layout of an ideal cold storage

24. Positive Impact:
 Temperature Control
 Texture and Appearance
 Microbial Growth
 Nutritional Value
 Shelf Life
Negative Effect:
 Texture Changes
 Flavor and Aroma Alterations
 Nutrient Loss
 Freezer Burn
 Drip Loss
 Quality Degradation over Time
 Potential for Microbial Growth
Effect of Refrigeration and Freezing on Fish Quality

25. In conclusion, a comprehensive understanding of the technological and
biochemical aspects of frozen products, along with the design and operation of
freezing plants and cold storage facilities, is essential for ensuring the quality,
storage life, and overall success of the frozen food industry. By addressing
these aspects effectively, manufacturers and suppliers can meet consumer
demands for high-quality frozen products while maintaining their freshness and
nutritional value.
Conclusion