Controlled Atmosphere Storage

Harvested fruit remains alive and respires, using oxygen and producing carbon dioxide as it slowly ripens and ages. Lowering the oxygen available and raising the carbon dioxide around the fruit reduces the rate of respiration, which in turn slows the metabolic changes that lead to softening, colour change, and loss of acidity. Cold storage already slows these processes; CA storage slows them further, so the effects are additive.

Each commodity, and often each cultivar, has its own tolerated atmosphere: oxygen that is too low, or carbon dioxide that is too high, can cause fermentation and physiological disorders rather than better keeping. For this reason CA conditions are matched to the specific fruit, and the atmosphere is monitored and adjusted throughout the storage season.

• Rooms are built and maintained gas-tight so the atmosphere can be held stable.
• Oxygen is drawn down and carbon dioxide is controlled using generators, scrubbers, and, increasingly, low-oxygen techniques.
• Temperature, humidity, oxygen, and carbon dioxide are monitored continuously and kept within commodity-specific ranges.
• Fruit is harvested at the correct maturity, since CA preserves condition but cannot improve poor-quality or over-ripe fruit.

The low-oxygen atmosphere that preserves fruit is dangerous to people: a CA room does not contain enough oxygen to support life, so entry requires strict confined-space and gas-testing procedures. Managed correctly, CA storage delivers fruit of high quality out of season, but it depends on good fruit at harvest, precise control, and reliable refrigeration.