Optimise controlled atmosphere storage techniques for selected pome and stone fruit cultivars

Oxygen (O₂) concentration, carbon dioxide (CO₂) concentration, storage temperature and controlled atmosphere (CA) storage period affected several quality parameters on Pioneer plums over a period of two seasons.  Low O₂ concentration (2%) and 5% CO₂ resulted in lowest internal breakdown and wilting compared to CO₂ concentrations of 0, 10 and 15% CO₂.  Fruit stored at CA storage for a period of 20 d developed a significantly lower incidence of internal breakdown than a 10 d CA storage period.  Fruit stored for 10 d at -0,5°C followed by 7,5°C had a significantly lower incidence of internal breakdown than fruit stored at 20 d or 30 d at -0,5°C.  Sunkiss, Sundew, Fortune and Lady Red plums were not tested at CA conditions, as instructed by the DFPT, but stored at dual temperature conditions simulating export conditions.  Sunkiss, Sundew, Fortune and Lady Red plums developed a 39,8%, 81,8%, 33,3% and 4% internal breakdown, respectively.

Quality of Rosemarie and Abate Fetel pears were best maintained in storage atmospheres containing 1,5% O₂, 1,0% CO₂; 1,5% O₂, 0% CO₂ or 1,5% O₂, 1% CO₂ and 1,5% O₂, 3,0% CO₂, respectively, for 5 months at a storage temperature of -0,5°C.  Quality of Flamingo pears could be maintained for 3 months storage in regular atmosphere or controlled atmospheres containing 1,5% O₂ and 0, 1 or 3% CO₂.  The development of mealiness in Forelle pears from the Grabouw and Ceres areas was not decreased by storage at a higher temperature (4°C) compared to the industry standard protocol of 8 to 10 w at -0.5°C.  Josephine pears could be stored under CA conditions for 8 m. at 1,5% O₂/1,0% CO₂ at -0,5°C and 1,0% O₂/3,0% CO₂ at 1°C without loss in fruit quality.  Rosemarie could be stored for 5 months employing a regular atmosphere (RA) storage of 14 d at -0,5°C followed by CA storage at 1,5% O₂/1,0% CO₂ at -0,5°C without loss in fruit quality.

An initial low oxygen stress treatment followed by CA storage at 1,0% O₂, in combination with 1,0%, 3,0% and 5,0% CO₂, respectively inhibited the development of superficial scald on Topred to less than 0,5% and had a 100% inhibition on Granny Smith apples after a 8 and 9 months storage period without the use of DPA.  The loss in post-storage quality of Packham’s Triumph pears, Golden Delicious, Topred, Royal Gala and Granny Smith apples was effectively minimised by CA storage at 1,0% O₂/3,0% CO₂ at temperatures of -0,5°C and 1°C for periods of 6, 7 and 8 months..  Flavour and quality of Royal Gala apples are influenced by O₂– and CO₂ concentrations during CA storage.  The best flavour and quality retention were obtained between 2 m. and 4 m. CA storage at 1,0% O₂/1,0% CO₂ ,1,0% O₂/3,0% CO₂ , initial oxygen stress followed by 1,0% O₂/3,0% CO₂ and 1,5,0% O₂/1,5% CO₂.

Pink Lady, Braeburn and Sundowner apples could be stored for 7 , 8  and 8 months in storage atmospheres containing 1,5% O₂, 1% CO₂, 1,5% O₂, 1,5% CO₂ and 1,5% O₂, 3% CO_2, respectively, at a storage temperature of -0,5°C without loss in fruit quality.  Results from the 2002 season show that Pink Lady and Sundowner apples picked at the optimum maturity could be stored for 7 and 9 months, respectively at atmospheres of 1,5% O₂ and 3% CO₂.  In South Africa there are indications that post-optimum maturity (wait for colour development) in combination with other factors are responsible for this defect.  Recommendation to industry since 2001 is to store this cultivar in atmospheres containing 1,5 O₂ and 1% CO₂ to lower the risk.  It is recommended that research on the storage of Pink Lady to detect the exact causal factor should continue under this project since it can be executed more cost-effectively.  The recommendations to industry for CA storage of Braeburn and Sundowner apples are 1,5% O₂ and 1,5% CO₂ and 1,5% O₂ and 2,5% CO₂ respectively.  Both Pink Lady and Sundowner apples are susceptible to superficial scald and have to be pre-storage treated with 1000 ppm diphenylamine.