Controlled atmosphere storage is a system for holding produce in an atmosphere that differs substantially from normal air in respect to CO2 and O2 levels. Controlled atmosphere storage refers to the constant monitoring and adjustment of the CO2 and O2 levels within gas tight stores or containers. The gas mixture will constantly change due to metabolic activity of the respiring fruits and vegetables in the store and leakage of gases through doors and walls. The gases are therefore measured periodically and adjusted to the predetermined level by the introduction of fresh air or nitrogen or passing the store atmosphere through a chemical to remove CO2.
The storability of fruits and vegetables is strictly related to their respiration rate, which is an expression of metabolic activity. Aerobic respiration requires O2, and results in CO2 and heat release. More than 95% of the energy released is lost as heat. The temperature decrease, in particular if helped by modification of the atmosphere leads to a reduction in respiration rate, and therefore to an increase in storage life in fruits with climacteric respiration.
Selection of the most suitable atmosphere depends on cultivars, stage of maturity, environmental and cultivation parameters. No one atmosphere is best for all produce, specific recommendations and cautions must be determined fro each crop over the range of storage temperature and periods.
A gas tight room is an obvious prerequisite for achieving a good controlled atmosphere. Thus it is necessary to make room walls gas-tight. In order to ensure that the walls were gas tight to CA storage they were lined with sheets of galvanized steel.
Doors may be mounted on a sliding rail, or, they may be mounted to open vertically on overhead rails, as pictured to the right.