Freezing Technology

2.1.4 Storage method

There are three methods of storing fish in ice on fishing vessels

Bulking:

                 The fish hold is a insulated chamber located at the near side of the Boat. It is divided into different compartments using wooden boards supported by an upright beam. A layer of ice at least 5 cm thick is spread over the bottom of a compartment followed by a layer of fish. Ice is then spread over the fish and around the edges so that the fish are not in direct contact with the sides of the board.

                 Further layers of fish and ice are added until a depth of about 45cm ice and fish is achieved, with a layer of 5 cm of ice at the top. A horizontal wooden board is now placed over the section. The wooden board must be supported by the stanchion structures, not by the fish and ice in the lower compartment. More fish and ice are added in the same way, again to a depth of 45cm. The operation is repeated until the compartment is full. Wooden boards and stanchions must be kept clean and out of direct contact with the fish.  

Shelving: The fish hold is divided into sections as it is for bulking but this time removable shelves spaced at about 23 cm are used for holding the fish. The lowest shelf is covered with a layer of at least 5 cm of ice. Fish are placed in rows on the ice and more ice is used to cover the fish to about 5 cm. Only one layer of fish is to be put on to each shelf. Shelves must be supported by stanchions, not by the fish and ice below.  

Boxing: Fish boxes come in a variety of sizes and materials. Ideally, a box should:

i.          Be strong and robust.

ii.          Be able to be stacked so that the weight of the top boxes are taken by the boxes below, not by the fish in the box below.

iii.         Be able to nest to save on stowage space when empty.

iv.        Be easily cleaned and, if necessary, sterilized.

v.          Allow ice melt-water to flow away outside the box below and not through it on to the fish in the lower box.

vi.       Have good thermal insulation.

Fish boxes should be used as follows

                  A layer of ice 5 cm thick should be placed in the bottom of the box, followed by a layer of fish. A thin layer of ice follows, interlacing fish and ice, until the box is almost full. The ice should be placed around the sides of the box as well as amongst the fish and the top layer of fish should be covered with at least 5 cm of ice. The box must not be over filled. This prevents crushing the fish when the boxes are stacked into the fish hold. When boxing fish, the fish hold does not require any compartments or Stanchions.

Refrigerated fish rooms

                 Some fish rooms not only have insulation but also have refrigeration facilities. Earlier this refrigeration is usually in the form of cooled grids and pipes on the roof of the fish room. Now-a-days a unit cooler with fan is placed in the chill room. It is important to get the maximum cooling effect from the ice that is allowed to melt. For this reason the temperature in the fish room should not fall below 0^oC. In order to prevent melting of ice, it is common practice for refrigeration to be used only before fishing starts when the vessel is carrying ice alone. Under these circumstances, the temperature can be below 0^oC.

Insulated boxes

               In small boat fisheries, insulated boxes are used to carry ice to sea, and for storing ice and fish, when fishing occupies only a short period. The size of the boxes depends on the size of the boat and the amount of fish normally caught in a day’s fishing. The ambient temperature will govern the amount of insulation required in the box, though about 10-15cm of expanded polystyrene is common. Insulated boxes for small fishing boats can often be made locally at low cost.