Normal atmosphere consists of 78% nitrogen (N2), 21% oxygen (O2) and 0.03% carbon dioxide (CO2). An unventilated container of fruit, with rapid respiration rates, can quickly change the atmosphere, reversing the normal levels of oxygen and carbon dioxide in less than 24 hours. That could be disastrous, because too little oxygen or too much carbon dioxide can lead to spoilage.
Atmospheric composition is important to fruit and vegetables because they ‘breathe’ or respire, consuming oxygen and producing carbon dioxide. Optimal atmospheric control can slow down the rate of produce respiration and delay ripening beyond what refrigeration alone can do.
Atmosphere management involves:
Atmospheric composition is important to fruit and vegetables because they ‘breathe’ or respire, consuming oxygen and producing carbon dioxide. Optimal atmospheric control can slow down the rate of produce respiration and delay ripening beyond what refrigeration alone can do.
Atmosphere management involves:
- Reducing oxygen
- Increasing or removing carbon dioxide
- Removing ethylene and other volatiles
Fresh air control
The amount of fresh air needed depends on the tolerance of the commodity to low levels of oxygen and high levels of carbon dioxide and ethylene, as well as the rate at which the commodity respires and produces ethylene.
Fresh air exchange:
- Protects some agricultural products by removing unwanted heat, ethylene, carbon dioxide and other gases produced by the cargo
- Helps prevent unwanted ripening and the accumulation of odors
- Ensures longer shelf life for many perishables
The fresh air exchange vent* can be set from 0 to 141cfm** (240cmh**) and air is drawn into the container at a controlled rate to provide ventilation for commodities. Fresh air ventilation is particularly useful for commodities that produce high levels of ethylene, like tomatoes and apples.
The fresh air ventilation technique is essential. However, excessive ventilation may result in freezing of the evaporator coils and will require additional defrosting to remove the build-up of ice.
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