Some Science

ON LOW OXYGEN FRUIT STORAGE

 

LOW OXYGEN STORAGE

Low Oxygen storage is now at the forefront of fruit storage for apples and pears. 

For optimal storage results fruit should be stored just above, but as close to the fruit's Low Oxygen Limit (LOL) as possible (typically below 0,7% for apples and pears). Storing at low oxygen levels can provide significant benefits compared to conventional controlled atmosphere (CA) storage. These benefits include control of superficial scald, improved colour and taste retention and significantly extended storage life. 

Fruit from different cultivars, seasons and growing regions have different LOL's.

Storing at oxygen levels below the fruit's LOL may result in unwanted fermentation which is detrimental to fruit. It is very important to be able to accurately and reliably determine the LOL and store just above this level. 

WHAT IS DYNAMIC CONTROLLED ATMOSPHERE (DCA)?

DCA is the latest evolution of CA storage for apples and pears and provides significant quality benefits compared to conventional CA storage. These benefits include control of superficial scald, improved firmness and colour retention, taste enhancement, and significantly extended storage life.

The concept of DCA involves the reduction of oxygen concentrations in the storage atmosphere to the lowest level that can be tolerated by the fruit without inducing anaerobic metabolism and thus fermentation. This point is referred to as the Low Oxygen Limit (LOL). Fruti from different cultivars, seasons and growing regions have different LOLs.

Storing apples below their anaerobic compensation point or low oxygen limit can destroy the fruit. It is very important to be able to accurately and reliably determine the LOL and store just above this level.

DCA technologies allow operators to adapt the oxygen level in the storage room in direct response to changes in the fruit’s physiology and thus store safely at optimal low oxygen levels.

REQUIREMENTS FOR DCA

DCA storage may be considered an enhancement to existing CA-stores, however there are a number of infrastructural requirements in order to accommodate the oxygen levels required for the approach. These requirements are:

  • Well sealed airtight CA stores (in order to maintain oxygen levels below 1%);
  • Adequate on-site nitrogen supply for oxygen removal;
  • High performance Carbon Dioxide (CO2) scrubbers or lime. 

 

HARVESTWATCH DYNAMIC CONTROLLED ATMOSPHERE – CHLOROPHYLL FLUORESCENCE

The HarvestWatch DCA-CF system allows operators to reliably detect the Low Oxygen Limit in fruit and to store safely with confidence at optimal low oxygen levels.

HarvestWatch 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.

There are currently more than 2500 commercial DCA rooms under HarvestWatch™ worldwide (as of 2019). The HarvestWatch™ system is supported by extensive global research and is the most is commonly used DCA technology commercially adopted worldwide. It is considered by many as the most successful of the DCA technologies.