Some Science



Maintaining the Oxygen (O₂) level in a refrigerated apple store at approx. 1.5% can increase the commercial storage life significantly. While there may be quality deterioration during storage of up to 12 months in conventional CA the fruit is generally of acceptable eating quality.


Low Oxygen storage is now at the forefront of fruit storage, and the benefits of storage below ~0.7% oxygen are well documented. These benefits include control of superficial scald, improved colour and taste retention, and significantly extended storage life.

The lowest oxygen level at which fruit can be safely stored is known as the Low Oxygen Limit (LOL). For optimal results the fruit should be stored as close to the LOL as possible.

Fruit from different cultivars, seasons and growing regions have different Low Oxygen Limits.

When storing at low oxygen levels where there is a risk of quality loss due to anaerobic metabolism, it is important to be able to accurately determine the Low Oyxgen Limit and store just above this level.


Dynamic Controlled Atmosphere searches for the Low Oxygen Limit, by adapting oxygen levels dynamically during the storage period and is based on a measurement of a biological response of the stored fruit under low oxygen conditions. – Zanella 2003

Requirements for DCA-CF

  • Well sealed CA rooms (Pressure frop from 25 to 188mm water gauge in longer than 30 minutes);
  • Adequate on-site Nitrogen supply
  • High performance CO₂ scrubbers that can operate at low CO₂ levels without adding Oxygen to the CA store.



The HarvestWatch Dynamic Controlled Atmosphere system is chemical free and allows operators to reliably detect the Low Oxygen Limit in fruit and to thus store safely with confidence at optimal low oxygen levels.

The HarvestWatch system directly measures the fruits response to low oxygen conditions by analysing the fluorescence intensity emitted from the chlorophyll in the skin of the fruit.

If the oxygen levels in the storage room become too low, the system indicated the fruit stress and allows for corrective measures to be taken.