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Apple controlled-atmosphere CA storage chamber Photo: Iqbal farooz · Pexels License · source ↗

Apple controlled-atmosphere (CA) storage

Controlled-atmosphere (CA) storage extends the marketable life of apple by lowering oxygen and raising carbon dioxide in a gas-tight refrigerated chamber, dramatically slowing respiration, ethylene production and ripening. Regular cold storage (0-1 °C, normal air) holds Delicious-group apples for 4-5 months; CA storage holds the same fruit for 7-9 months without softening. In Jammu & Kashmir, large CA-storage clusters have come up at Sopore, Shopian, Pulwama and Lassipora, mostly built under NHB / MIDH / J&K HADP subsidy and operated by private aggregators and primary processing cooperatives.

Principle

Apple fruit continues to respire after harvest — consuming sugars and starch, producing CO₂, and emitting ethylene, the ripening hormone. The post-harvest life of a Delicious-group apple is dominated by these processes. CA storage manipulates the gaseous environment to slow respiration:

  • Temperature: 0-1 °C for Delicious, 1-2 °C for Ambri and Granny Smith
  • Relative humidity: 90-95% to prevent shrivelling
  • Oxygen: reduced from 21% (air) to 2-3%
  • CO₂: raised from 0.04% to 1-2%
  • Ethylene: scrubbed with KMnO₄ ("Purafil") or catalytic burners

Newer ultra-low-O₂ (ULO, 1-1.5% O₂) and dynamic CA (DCA, oxygen reduced to fluorescence-detection threshold) extend life further but require precise control to avoid CO₂ injury and core flush.

Procedure

  • Harvest at correct maturity: starch-iodine pattern in zones 4-5; firmness around 8 kg-force; soluble solids 12-14 °Brix for Red Delicious and Royal Delicious. Pre-harvest calcium chloride sprays reduce bitter pit during long storage.
  • Pre-cooling: forced-air pre-cooling at 0-1 °C within 24-48 hours of harvest, reducing fruit core temperature from field 18-20 °C to 2 °C.
  • Loading: graded fruit packed in CFB cartons stacked on pallets; entire chamber loaded and sealed within 7-10 days.
  • Pull-down: oxygen reduced gradually using a nitrogen generator (PSA / membrane); CO₂ scrubbed with lime or activated-carbon scrubber.
  • Hold and monitor: gas composition and temperature monitored with paramagnetic O₂ analyser and infrared CO₂ analyser; ethylene scrubbed continuously.
  • Outturn: chamber opened in tranches; fruit re-conditioned at 4 °C for 24 hours before dispatch.

Where it applies

CA storage is best suited to:

  • Long-storing cultivars: Red Delicious, Royal Delicious, Granny Smith, Fuji
  • Operations with steady supply of pre-cooled fruit
  • Markets willing to pay premium for winter / spring apples (Mumbai, Bangalore, Chennai, Gulf exports)

Major Indian CA clusters: Lassipora (Pulwama), Sopore, Shopian, Khalsi (Solan, HP), Parwanoo (HP). NHB subsidy under MIDH covers up to 35-50% of capital cost for CA cold stores ≥ 1,000 t capacity.

Limitations

  • High capital cost: ₹4-6 crore per 1,000 t CA chamber
  • Cultivar-specific gas regimes: a mistake (e.g. low O₂ in a sensitive lot) causes brown-core, scald and total loss
  • Requires uninterrupted power and trained CA technician
  • CA-stored fruit must be marketed within 7-14 days of de-stocking — short shelf life after exit

See also: Royal Delicious, Red Delicious, Ambri, HDP, chilling units.

Sources

  1. Apple Controlled Atmosphere Storage. ICAR-CITH Srinagar.
  2. CA Storage of Apple. HRRS Mashobra, Dr YS Parmar University.
  3. Apple Cold Chain and CA Storage. National Horticulture Board.