Cold Storage Systems

A cold room can be defined as an area isolated from heat and moisture gain from the outside atmosphere, where it is cooled and humidity controlled under ideal conditions so that the foodstuffs can be stored for longer than normal periods of storage. The goal in cold storage should be providing constant temperature and relative humidity as much as possible. Even for a very short period of time, each temperature increase causes acceleration in the number of microorganisms. Therefore, cooling should be applied to a germ-free product and maintained continuously from production to consumption. However, the storage period is limited and depends on the products.

In cold rooms , delaying the chemical enzyme reactions and delaying the growth of microorganisms, food stuffs can be kept very close to their original state. Cooling may also delay the proliferation of the microorganism population, may also result in the death of a limited number of deteriorating microorganism. For this reason, it is important to protect the products from microorganism infection at the beginning.

The temperature and relative humidity balance in a cold storage vary depending on the following factors:

  1. Properties of the product and its packaging to be placed in a cold store

    The changes in the density of the transpiration of the product in the cold room have a great effect especially when the product starts to be cooled.

  2. Stacking type of Cold Storage

    Stacking should be done while products are placed in cold rooms so that they do not interfere with free circulation of air. This ensures that the cold air inside the room is adequately and easily mixed so that the tempreture remains wihtin the appropriate limits.

  3. Surface areas and constructions of evaporators

    The surface areas of the evaporators, the number of fans, the cross-sectional areas of the fans, the air flow of the fans directly affect the humidity and temperature of the cold storage .

  4. Difference Between Evaporator Surface Temperature and Room Temperature

    Care must also be taken to keep the temperature difference between the refrigerant and the cold room as small as possible , taking into account losses occurring due to the calculated heat permeability .

    In practice, a difference of 5 ºC between the average temperature of the cold room and the refrigerant temperature can be considered reasonable.

    If the difference between the cold room average temperature and the refrigerant temperature is more than 5 ºC, its starts to condensation water vapor in the air; this can cause frosting in the evaporator.

  5. Isolation of Cold Storage

    In cold storage, the type and thickness value of the isolation material is extremely important.

    Cold storage isolation is usually done in two forms. the first form is classical ( constructional type ) cold storage isolation, in constructional type isolation;

  • Styrofoam plates
  • Extruded polystyrene plates
  • Polyurethane plates are the main materials used.
  • The second and modern method used in cold storage isolation is prefabricated panel application with polyurethane filling
  • Practical, fast installation and disassembly feature,
  • Providing savings from time and place,
  • Up to 40% energy savings,
  • Easy cleanability,
  • The use of hygienic and durable surface materials,
  • Reusable and portable
  • Controlling by the eye makes the panel isolation essential.
  1. Air Distribution circle in Cold Storage

    Air movement or circulation in the cold air storage should be such that an equal temperature and humidity should occur in all volumes. Excessive air movement can cause water loss in foodstuffs. This situation is both unnecessary and harmful. Corresponding qualified air distribution is useful and necessary. If storage is poor and prevents air distribution, channeled air distribution should be preferred in cold storage.

  2. Operation time of cold room equipments

    The operating time of cold room devices depends on room temperature, evaporation temperature and daily frost period. The total daily working times of cold room equipments can be considered as 16-18 hours depending on the type of product to be kept.

    The temperature and humidity characteristics and storage conditions of some foodstuffs are given bellow.

  3. Cold Storage Temperature Ranges and Storage Types
  4. Chilly storage ( +5ºC / +15ºC)
    The temperature range of some special foodstuffs (green pepper, tomato, bananas, etc.) and food processing areas.

    Cold storage ( -5ºC / +5°C)
    Most of the freshly preserved foodstuffs are stored at this temperature range.

    Frozen storage ( -15ºC / -25°C)
    All frozen foods are stored at this temperature range. Frozen storage is to keep the temperatures of products that have been previously quick freezed and lowered to -18ºC from the center temperature.

    Quick Freezing ( -30ºC / -45°C)
    Quick Freezing is not a type of storage, but it is useful to identify it with the reasons of faults in general. Quick Freezing is the process of lowering the central temperatures to -18 ºC in a short time like 4-7 hours. The size of the cold or frozen cold storage depends on the amount of product to be stored, the type of product and packaging. In addition, the previously known or specified tank height is also effective in sizing.