If warm produce is taken into a cold store, moisture will evaporate from its surface and this may result in excessive humidity and condensation on the cold produce already there. This will be of no consequence with wet products such as fish and leaf vegetables. Meat and poultry is pre-cooled in a separate room under controlled conditions so that the product is reduced to near-final storage temperature.

Pre-cooling can be achieved by allowing produce to stand in ambient air, especially at night. For example, apples and pears picked in the daytime at 25°C may cool down to 12°C by the following morning, halving the final refrigerated cooling load.

Wet products can be pre-cooled in chilled water or by the addition of flake ice. Ice is also used with fish and leaf vegetables to help maintain freshness in transit to storage. Leaf vegetables can be cooled by placing them in a vacuum chamber and so evaporating surface water at low pressure.

Posted in Refrigeration and Air Conditioning