For many years produce has been cooled by simply storing it in a refrigerated room, a process known as room cooling. This method is generally sufficient for keeping produce at a low temperature once it has been cooled, but it often does not remove field heat rapidly enough to maintain the quality of highly perishable crops. Room cooling is very often inadequate for produce stored in large containers, such as bulk boxes or pallet loads, and for produce that requires immediate cooling.
In the room cooling process, heat is removed slowly from only that produce near the outside of the container. Near the center of a container, heat is often generated by natural respiration more rapidly than it can be removed, causing the temperature to rise. Some types of produce, such as strawberries, must be cooled as quickly as possible after harvesting to preserve its fresh quality. Even a delay of several hours may be enough to reduce quality considerably. In such cases, room cooling is not fast enough to prevent serious damage.
To preserve quality, fresh produce should be cooled to its lowest safe (optimum) storage temperature as quickly as is practical and economical. Forced-air cooling is much faster than room cooling and is being used increasingly in North Carolina to cool produce quickly. It offers these advantages:
- It decreases the time the produce remains at elevated temperatures, thereby reducing deterioration;
- It results in shorter cooling times and thus more efficient use of the cooling facility;
- It can cool produce effectively in a variety of unopened containers without wetting it or subjecting it to excessive handling;
- It is often more energy efficient than room cooling when large volumes of produce must be cooled;
- An available room-cooling facility with adequate cooling capacity can be converted to forced-air cooling with only a relatively small investment in fans