Chapter 6

Recommended Temperature and Gas Regimes for Cold Storage of South African Commercial Apple and Pear Cultivars

Compiled by ARC Infruitec-Nietvoorbij in co-operation with SA Apple & Pear Producer’s Association
Revised and updated annually by Anél Botes; ARC Infruitec-Nietvoorbij; JA van der Merwe (Consultant HGS), January 2019

IDEAL STORAGE CONDITIONS

Temperature

• RA-storage: Core temperature must be -0.5°C within 48 hours of harvest. Hold at -0.5°C for storage duration.
• CA-storage: Core temperature must be -0.5°C within 96 hours (4 days) from harvest.
  • Rapid removal of field heat to -0.5°C is more beneficial than rapid attainment of the required gas regime.

Relative Humidity (RH)

• Must be between 90% and 95%.
• Applies to both RA and CA storage.

Gas Regime

• Nitrogen flushing: Must reach 3% O₂ + 1.5% CO₂ (0% CO₂ for Bon Chretien and Forelle) within 4 days of sealing the room.
• Nitrogen generator: Must reach 3% O₂ + 3% CO₂ (0% CO₂ for Bon Chretien and Forelle) within 48 hours of sealing the room.

Important Notes

• Bon Chretien:
  • Can be handled after extended CA-storage if only fruit of optimum maturity is stored and the cold chain is strictly maintained.
  • Must be stored at 0% CO₂.
• Forelle:
  • Mature Forelle pears from certain areas are prone to CO₂ injury and should be stored at 0% CO₂ if possible.

MINIMUM STORAGE CONDITIONS

Loading of CA Room

• Orchard run fruit: Loading should not exceed 7 days; effective cooling must take place.
• Pre-sized fruit: Loading may take up to 14 days from beginning of harvest. Minimum gas regimes must be reached within 7 days of sealing the room (total of 21 days from beginning of harvest).
• Exception: For Packham’s Triumph picked in week 7 stored with Golden Delicious/red cultivars picked in ± week 9:
  • Total loading time should not exceed 21 days.
  • Minimum gas regimes (3% O₂) must be attained within 7 days of sealing the room.
  • Maximum number of days for the whole operation: 28 days.

Temperature

• RA and CA-storage: Fruit must be placed under refrigeration within 24 hours from start of harvesting.
• Core temperatures after sealing the room:
  • Bon Chretien: 2 days to 2°C + 2 days to -0.5°C (total 4 days)
  • Other cultivars: 3 days to 2°C + 3 days to -0.5°C (total 6 days)
• Forced air cooling should be used to attain these temperatures.

Gas Regimes

• Prescribed gas regimes must be reached within 7 days of sealing the room.

APPLES

IDEAL STORAGE CONDITIONS

Temperature

• Golden Delicious, Starking, and other red cultivars: Cool to -0.5°C within 48 hours of harvest and hold at that temperature.
• Granny Smith:
  • Cool to 3°C within 48 hours after harvest and hold for 10 days, then cool to -0.5°C as quickly as possible; or
  • Cool to 0°C within 48 hours, then lift storage temperature to +0.5°C and hold for storage duration.

Relative Humidity (RH)

• Must be between 90% and 95%.

Gas Regimes

• Nitrogen flushing: Attain 3% O₂ + 1.5% CO₂ within 48 hours of sealing the room. CO₂ must not exceed 2.5% during pull-down (except Golden Delicious: max 5%).
• Nitrogen generator: Attain 3% O₂ + 3% CO₂ within 48 hours. Same CO₂ limits as above.

MINIMUM STORAGE CONDITIONS

Loading of CA Room

• Orchard run fruit: Loading should not take longer than 7 days; effective cooling must take place.
• Pre-sized fruit: Loading may take up to 14 days from beginning of harvest; minimum gas regimes must be reached within 7 days of sealing the room (total 21 days).
• Exception: For Packham’s Triumph pears picked in week 7 stored with Golden Delicious/red cultivars picked in ± week 9:
  • Total loading time may not exceed 21 days.
  • Minimum gas regimes must be attained within 7 days of sealing the room.
  • Total 28 days for the whole operation.

Temperature

• Place fruit under refrigeration within 24 hours from start of harvesting.
• Core temperatures after sealing the room:
  • Granny Smith: 4 days to 3°C + 10 days to -0.5°C or +0.5°C (total 14 days)
  • Other apples: 4 days to 2°C + 3 days to -0.5°C (total 7 days)

Gas Regimes

• Should be reached within 7 days of sealing the room (i.e., within 14 days from start of harvesting):
  • Granny Smith: 3.0% O₂, 1.0% CO₂
  • Other cultivars: 3.0% O₂, 1.5% CO₂
  • Note: CO₂ levels should never exceed 2.5% (except Golden Delicious: max 5%).

APPLES & PEARS

Interruption of CA Storage

• If CA conditions are interrupted, a total period of 21 days (including pull-down) above 2.5% O₂ may not be exceeded. Otherwise, fruit should not be regarded as CA-stored.

Measuring Oxygen Concentrations

• Oxygen concentrations in CA rooms to be measured at least once weekly at the room itself with a portable analyser.
• This is additional to the existing control system (O₂ levels measured at least twice daily).

Tolerance

Temperature Range

• Minimum: -0.5°C
• Maximum: 1.0°C

Minimum Storage Period

• Minimum storage period under conventional CA conditions for pears and apples to qualify as CA fruit: 60 days

Log Sheet (See Appendix 3)

• Computer printouts and standard log sheets may be used.
• The following information must be monitored (at least twice daily):
  • Air delivery and return temperature
  • Fruit core temperatures (front and back of room)
  • Oxygen and carbon dioxide readings

Important Dates to Record

• Start harvesting
• Start pre-cooling (if any)
• Start loading the room
• Date of sealing the room

Export Fruit in CA Storage

• Pears and apples stored under CA conditions for export must be treated as for the local market, except for dipping and drenching treatments.
• Producers should apply recommendations supplied by ARC Infruitec-Nietvoorbij and comply with directions of manufacturers.

Safety Precautions

• CA operators should be aware of the content of the safety procedures applicable to CA rooms.

APPENDIX 1

Recommended Gas Regimes and Storage Periods for Pears

APPENDIX 2

Recommended Gas Regimes and Storage Periods for Apples

Abbreviations:

• DCA = Dynamic Controlled Atmosphere storage
• SF = Smartfresh (1-MCP)
• RLOS = Repeated Low Oxygen Stress

APPENDIX 3

Log Sheet

ROOM NO.:
PICKING TIME: FROM __ TO __
PRE-COOLING TIME (DAYS):
Cultivar:
LOADING TIME (DAYS):