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Wednesday, November 25, 2009

REEFER CONTAINER MODIFIED/CONTROLLED ATMOSPHERE

When using the modified atmosphere technology, a container is purged of most gases first before a new mixture of gases - at optimum levels and amounts for the commodity being shipped - is injected into the container after it has been sealed. This modified atmosphere technology is a supplement to temperature management that provides more precise control than fresh air exchange. It is effective in slowing respiration and retarding the production of ethylene in horticultural commodities. Lettuce, for example, can be transported across the Pacific using modified atmosphere with excellent results. The modified air content of a container, however, can change during a trip due to the respiratory activity of the commodities and pressure changes in the container, thereby reducing its effectiveness at retarding the deterioration of fresh produce.

Controlled atmosphere is the most technologically advanced process that is used to precisely control the atmospheric composition within the container throughout a shipment's entire journey. Controlled atmosphere can increase the post-harvest life of some perishables by two to three times longer than other methods.

Controlled atmosphere technology uses computer systems to monitor and control the atmosphere in the container and make adjustments during the trip. These systems also record changes in the atmospheric composition during a container's journey and provide a printout for quality-control purposes.

Excellent out-turn of asparagus after 18 days of voyage under 10% O2 and 10% CO2 controlled atmosphere condition.

The composition of the controlled atmosphere transport is commodity-specific. Atmospheric conditions are custom-tailored to provide an optimum environment for each commodity. The availability of controlled atmosphere is important in opening new markets for shippers, allowing the ocean carriage of commodities previously transported by airfreight. Controlled atmosphere can also be used to meet the needs of a particular market by manipulating the ripening rate of fruits and vegetables. Some of the products benefiting from controlled atmosphere include sweet cherries, nectarines, peaches, broccoli, asparagus, avocados, mangoes, cut flowers and chilled meat.

Successful shipping of these commodities is supported by many years of university and industry research. MA and CA differ only in the degree of control. However, CA is more precise in controlling the level of gases. In summary, the following are the key potential benefits of MA/CA shipment which of course is dependent upon the commodity, variety of cultivars, duration of storage, correct post-harvest handling and proper temperature management (most critical factor).

Retard ripening and slow down respiration, ethylene production rates.

Direct or indirect effect on post-harvest pathogens, reduce decay incident and severity.

Alleviate certain fruit physiological disorders such as chilling injury.

Useful tool for insect control in some commodities to meet quarantine requirements of importing countries.

Appropriate level of gases (O 2 & CO 2 ) is essential to attain the potential benefits.