Status of
low temperature storage and its potential
The
estimated annual production of fruits and vegetables in most countries around
the world is about 130 million tonnes. This could accounts for 18% of the
country`s agricultural output. Due to diverse agro climatic conditions and
better availability of package, the production is gradually rising. However,
there is a vast scope for increasing the production, the lack of low
temperature storage and low temperature chain facilities are becoming major
challenges in tapping the potential. The cold storage facilities now available
are mostly for a single commodity like potato, orange, apple, grapes,
pomegranates, flowers and so on, which could then results in poor capacity
utilization.
Storage of
foods and conditions of storage
Commodities and
most foods can be preserved by storage at low temperature, which could then retards
the activities of micro organisms. Micro organisms are the spoilage agents of
foods and they consist of bacteria, yeasts and molds. Low temperature does not
destroy those spoilage agents as does of 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. The low
temperature which necessary for preservation food depends greatly on the
storage time which is required often referred to as short or long term of shortage
and the type of product which is to be stored. In general, there are three
groups of products in storage which are foods that are alive at the time of
storage, distribution and sale such as fruits and vegetables, foods that are no
longer alive and have been processed in some form such as meat and fish
products and commodities that benefit from storage at controlled temperature such
as beer, tobacco and so on.
Size of system
of trade and industry unit and land needed
Low temperature
storage units can be used to store either a single commodity as well as
multiple commodities. This greatly depend upon the entrepreneur's financial
health; it can be planned to store the produce entirely owned by him or on
rental basis or could be in combination of the two. It is a good practice to
consider low temperature storages where 70% of the capacity is available to
farmers for storage on rentals. The financial viability of a unit for storage depends
upon the intended pattern of use and rental rate prevalent in an area. However,
the units to be used by the owners are also considered for sanction.
Considering 70:30 utilization of the capacity for rentals and own use, a 5000
MT capacity unit is considered as viable with the assumptions. To put up a 5000
MT capacity low temperature storage unit, one acre of land may be required, it
is always better to have two acres of land to take care of future expansions
and waste management. While selecting the site of storage of farm, care should
be taken to select a site at an elevation free from inundation and well
connected by road and other communication facilities to both production and
consumption centers. The land for storage should be of non agricultural type
and the soil at the site should be firm enough to carry the weight of the
building as well as the storage racks for the storage operation.
The technology
of storage
A low
temperature storage unit should incorporate a refrigeration system to maintain
the desired room environment for the commodities or food to be stored. A
refrigeration system works on two principles namely vapour absorption system
and vapour compression system.
Vapour absorption
system is comparatively costlier, but 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 shortcomings when temperature requirement is below 100C and many
of the fruits and vegetables except seeds, mango and so on, require lower than
100C for long storage to be effective.
Vapour compression
is comparatively cheaper than vapour absorption system. There are three types
of vapour compression systems which are available depending upon the cooling
arrangements in the storage rooms, which is the diffuser type, bunker type as
well as the fin coil type. Diffuser type is comparatively costlier and is
selected only when the storage room heights are low in nature. The operational costs
of such units are also higher. Bunker type is the cheapest and is preferred
when storage room heights normally exceeds 11.5 m. Its operational cost is also
low. The 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 the produce. Such system is used for units with room heights of 5.4m
onwards.
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