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The most common plate freezers are those with a multi-plate freezer type. In a
well-insulated cabinet, several shelf-shaped slabs are arranged in a row. The effectiveness of plate freezers depends on the degree of contact between the product and
the plate. The time of freezing depends on the type and thickness of the packaging
material, the type of the product being frozen, the initial temperature and the thickness of the product (Cemeroglu et al. 2003).
Air Blast Freezing
In this method, the temperature of the food is reduced by the cold air flowing at a
relatively high speed. Air blast freezers are systems that allow the cold air to circulate over the product which will be frozen with the help of fans. With the help of
powerful fans, the moving air cools down as it passes through the evaporator and
then rapidly passes through the frozen product. The air temperature in the freezer is
−30 to −40 °C and the air velocity is 4–6 m/s (Gokoglu 2002). Lower air velocities
cause freezing of the product slowly and high speeds significantly increase unit
freezing costs (Rahman and Velez-Ruiz 2007). These types of freezers have a wide
range of use in the freezing of packaged or unpackaged products of different shapes
and sizes, in pans, trays and trolleys, in cabinets or on conveyor belts, individually
or in blocks. Therefore, it is a commonly used freezing method. This method can
also be divided into tunnel freezing, belt freezing and fluidized bed freezing depending on how the air interacts with the product.
The most common of these is tunnel type freezers. In the tunnel freezers, the
product to be frozen is transported by a belt or by the movement of trays or racks in
the tunnel. The movements of the product to be frozen and the cold air in the tunnel
may be parallel or opposite. In opposite current tunnels, the product is given from
one side of the tunnel and cold air from the other side.
In some tunnels, cold air is blown upwards from the bottom of the belt. With the
fast air blowing, the substances on the belt are kept in a position as floating in the
air. In this system, called as fluid bed freezers, a very fast freezing is performed on
all sides of the particles that rise and fall in the air and full contact with the cold air.
In this way, the individual freezing of each part is called “individual quick freezing”
(IQF). This is a system that can be applied easily to products that are small enough
to form a homogeneous and fluidized bed. In addition to the advantages of this system, the electrical energy consumed by the fans is very high. For a product to be
frozen in the fluidised bed system, the product must be in small parts to be able to
flow in a certain air stream. The individual freezing process (IQF) allows the shellfish to freeze quickly and in consumable quantities. IQF is a suitable method for
products such as shrimp, scampi tail meat, squid fillet, squid rings and pectin
(Venugopal 2006).
A spiral belt freezer consists of a long belt, wrapped in cylindrical form in two
layers, thus requiring less space. The spiral freezer uses a laterally twisting conveyor belt. It is suitable for products with long freezing time (usually 10 min to 3 h)
and for sensitive products. A belt located in an insulated cabin follows the spiral
path from bottom to top, while cold air is supplied from the sides. The spiral shape
2.1 Shrimps/Prawns
The most common plate freezers are those with a multi-plate freezer type. In a
well-insulated cabinet, several shelf-shaped slabs are arranged in a row. The effectiveness of plate freezers depends on the degree of contact between the product and
the plate. The time of freezing depends on the type and thickness of the packaging
material, the type of the product being frozen, the initial temperature and the thickness of the product (Cemeroglu et al. 2003).
Air Blast Freezing
In this method, the temperature of the food is reduced by the cold air flowing at a
relatively high speed. Air blast freezers are systems that allow the cold air to circulate over the product which will be frozen with the help of fans. With the help of
powerful fans, the moving air cools down as it passes through the evaporator and
then rapidly passes through the frozen product. The air temperature in the freezer is
−30 to −40 °C and the air velocity is 4–6 m/s (Gokoglu 2002). Lower air velocities
cause freezing of the product slowly and high speeds significantly increase unit
freezing costs (Rahman and Velez-Ruiz 2007). These types of freezers have a wide
range of use in the freezing of packaged or unpackaged products of different shapes
and sizes, in pans, trays and trolleys, in cabinets or on conveyor belts, individually
or in blocks. Therefore, it is a commonly used freezing method. This method can
also be divided into tunnel freezing, belt freezing and fluidized bed freezing depending on how the air interacts with the product.
The most common of these is tunnel type freezers. In the tunnel freezers, the
product to be frozen is transported by a belt or by the movement of trays or racks in
the tunnel. The movements of the product to be frozen and the cold air in the tunnel
may be parallel or opposite. In opposite current tunnels, the product is given from
one side of the tunnel and cold air from the other side.
In some tunnels, cold air is blown upwards from the bottom of the belt. With the
fast air blowing, the substances on the belt are kept in a position as floating in the
air. In this system, called as fluid bed freezers, a very fast freezing is performed on
all sides of the particles that rise and fall in the air and full contact with the cold air.
In this way, the individual freezing of each part is called “individual quick freezing”
(IQF). This is a system that can be applied easily to products that are small enough
to form a homogeneous and fluidized bed. In addition to the advantages of this system, the electrical energy consumed by the fans is very high. For a product to be
frozen in the fluidised bed system, the product must be in small parts to be able to
flow in a certain air stream. The individual freezing process (IQF) allows the shellfish to freeze quickly and in consumable quantities. IQF is a suitable method for
products such as shrimp, scampi tail meat, squid fillet, squid rings and pectin
(Venugopal 2006).
A spiral belt freezer consists of a long belt, wrapped in cylindrical form in two
layers, thus requiring less space. The spiral freezer uses a laterally twisting conveyor belt. It is suitable for products with long freezing time (usually 10 min to 3 h)
and for sensitive products. A belt located in an insulated cabin follows the spiral
path from bottom to top, while cold air is supplied from the sides. The spiral shape
2.1 Shrimps/Prawns