Cold Storage is one of those terms that you often hear but never fully understand, so what exactly does it mean in the context of the fresh produce supply chain?
Cold Storage, also referred to in certain contexts as Frozen Storage, Chilled Storage, Refrigerated Storage and Cool Rooms, simply refers to a storage facility that involves some type of refrigeration to maintain temperature-controlled rooms.
While that may be a simple reduction of what cold storage consists of, these days cold storage services go beyond just providing cool rooms but also, controlled atmospheres, supply chain analytics, and data storage.
Storage of foods and storage conditions
Fresh produce can be preserved by storage at low temperature, which retards the activities of microorganisms. Microorganisms are the spoilage agents and consist of bacteria, yeasts and moulds. Low temperature does not destroy those spoilage agents as does high temperature but greatly reduces their activities, providing a practical way of preserving perishable foods in their natural state which otherwise is not possible through heating.
Living foods such as fruits and vegetables have some natural protection against the activities of microorganism. The best method of preserving these items is to keep the product alive and at the same time slow down the natural enzyme activity which will slow the rate of ripening or maturity. Which is why cold storage warehouses are dedicating specific spaces towards the required temperature settings of specific fruit and vegetable groups.
Only certain fruits and vegetables can benefit from freezing. However, for fruits and vegetables, you must be very careful about the recommended storage temperature and humidity, as any shift in temperature can have a negative effect on the products leading to an even greater loss of the entire batch.
Products such as apples, tomatoes, oranges, etc. cannot be frozen and close control of temperature is necessary for long term storage. Some product can also be benefited by storing under controlled atmosphere and modified atmosphere conditions.
A cold storage unit incorporates a refrigeration system to maintain the desired room environment for the commodities to be stored. A refrigeration system works on two principles:
- Vapour absorption system (VAS), and
- Vapour compression system (VCS)
VAS, although comparatively costlier, is quite economical in operation and adequately compensates the higher initial investment. Wherever possible such a system should be selected to conserve on energy and operational cost. However, it has its own limitations when temperature requirement is below 10°C and many of the fruits and vegetables except seeds, mango, etc. require lower than 10°C for long storage.
VCS is comparatively cheaper than VAS. There are three types of VCSs available depending upon the cooling arrangements in the storage rooms:
- Diffuser type is comparatively costlier and is selected only when the storage room heights are low. The operational cost of such units is also higher.
- Bunker type is the cheapest and is preferred when storage room heights normally exceed 11.5 m. Its operational cost is also low.
- Fin coil type, although about 5% costlier than the bunker type, is very energy efficient with low operational cost and higher space availability for storage of produce. Such a system is used for units with room heights of 5.4m onwards.
If you’d like to know more about Cold Storage, checkout PostHarvest’s free online course.