What is Cold Storage for Fresh Produce?
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 preservation involves storing items at low temperatures, which effectively slows down the activities of spoilage microorganisms such as bacteria, yeasts, and molds. Unlike high temperatures that can destroy these microorganisms, low temperatures reduce their activities, offering a practical means of preserving perishable foods in their natural state without the need for heat treatment.
Living foods like fruits and vegetables possess natural defenses against microorganisms. The most effective method of preserving such items is by maintaining their freshness and concurrently slowing down natural enzyme activity, which helps extend the ripening or maturation process. Cold storage warehouses allocate specific spaces tailored to the required temperature settings for distinct fruit and vegetable groups.
Freezing is a preservation method suitable for specific fruits and vegetables. However, precise control over storage temperature and humidity is critical, as any deviations can adversely affect the products, potentially leading to substantial losses in the entire batch. Certain products, including apples, tomatoes, oranges, and others, cannot withstand freezing, requiring meticulous temperature control for prolonged storage. Additionally, some products may benefit from storage under controlled atmosphere and modified atmosphere conditions.
Technology
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.