Which is the technology behind shipping of perishable commodities? What makes fruits and vegetables may arrive to consumers in perfect condition is transportation technology?
Consumers usually do not wonder why bananas harvested in Ecuador or kiwis from Australia may be at the corner store in suitable condition for consumption.
A sea crossing of 4 to 6 weeks, in addition to land transport at origin and destination, seems to be a big challenge, but certain issues related to procedures and technology are taken into account to ensure product quality for the foreign consumer.
Before reefer containers released to customers, they must always pass through a pre-trip inspection, which consists of a long and extensive check of the container and the operation of the reefer machinery.
The goal is to ensure that the customer receives only clean and undamaged containers with reefer machinery in perfect condition.
Internal air circulation is essential for maintaining prescribed temperatures in reefer containers. Cold air is constantly circulated through the cargo space to dissipate transmitted heat.
This air is blown in at the bottom of the refrigeration unit through the gratings in the ducted floor and then drawn off again below the container ceiling.
The circulating fans then force the air through the air cooler, which also acts as the evaporator in the cold circuit, and back through the gratings into the cargo.
Each commodity has different air flow requirements. Inside a reefer container the air flow is influenced by the type of packaging and the method of stuffing used.
In reefer containers, there are two standard loading patterns for perishable products: block stow of break bulk cargo and palletized cargo stowage.
The height of the cargo must not exceed the red cargo load line, which shows maximum allowed cargo height, so that ample free space is left above the stow to ensure proper air circulation around the load.
Fresh air ventilation
During transport, fresh fruit and vegetables continue to respire and thus produce gases such us carob dioxide and ethylene.
As these respiratory gases can lead to cargo damage such as uncontrolled ripening, ageing and off-flavour, they have to be removed from the container atmosphere.
Depending on the respiration rate of the commodity, ventilation vents of a reefer container are usually opened at defined set-points in cbm/h for most fresh fruit and vegetables.
Proper temperature control is the most important factor in maintaining the quality of perishable commodities, because once temperature deviations occur, they cannot be reversed.
For optimal quality, it is therefore critical to maintain proper temperatures from origin all the way to the end consumer.
Modified Atmosphere (MA) and Controlled Atmosphere (CA) have become effective means of securing and preserving cargo quality.
During transport, post-harvest processes on fruit and vegetables are generally minimized through temperature control and fresh air ventilation. In order to reduce them even further, MA and CA containers have been developed.
This special type of reefer equipment can specifically change the gas composition of the container atmosphere in order to enhance the effect of refrigeration and thereby prolong product shelf life.
MA is a partly controlled change of air composition, while CA means the technology for constantly measuring and actively maintaining the atmospheric conditions in a reefer container throughout the journey of the shipment.
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