Determine optimum controlled atmosphere storage conditions for Abate Fetel pears

Objective and rational:  Determine the optimum CA storage conditions for Abate Fetel pears in order to advise industry on the optimum CA storage conditions to maintain the best fruit quality.

Methodology:  Completely randomized research trials to determine the optimum CA storage conditions were conducted on Abate Fetel pears at optimum picking maturity from the Ceres and Grabouw production areas.  Fruit were stored at CA conditions of 1.5% O₂ in combination with 0, 1 and 2.5 %CO₂ during 2012 season and at additional storage treatments of 6 and 8% O₂ and 0% CO₂ during the 2013 and 2014 seasons respectively.  Storage temperature was at -0.5°C for periods of 4 and 6 months followed by a simulated shipment period of 4 w at RA storage and shelf life periods of 0 and 7 d at 20°C.  Fruit quality were evaluated after 4 and 6 months according to industry standards.  Data was statistically analysed and progress reported annually.

Main conclusions:

• During the 2012 season Abate Fetel pears from both the Grabouw and Ceres production areas stored at CA 1.5% O₂+1% CO₂ were of the best post storage quality after a storage period of 4 months and a simulated storage period of 4 w RA at -0.5°C followed by a shelf life period of up to 7 d at 20°C.  The fruit were susceptible to CO₂ damage (2.5%) and CO₂ gas regimes with a CO₂ concentration of between 0-1% were tested during the 2013 season.
• During the 2013 season Abate Fetel pears from the both Grabouw and Ceres production areas stored at CA 1.5% O₂+0% CO₂ were of the best post storage quality after a storage period of 4 and 6 months and a simulated shipment period of 4 w RA at -0.5°C followed by a shelf life period of up to 7 d at 20°C.  Higher O₂ storage regimes (8%) also showed promising results.  Storage of Abate Fetel pears at storage regimes of 1.5% O₂ +0% or 1% CO₂ with good quality confirmed susceptibility to high CO₂ during storage.

• During the 2014 season Abate Fetel pears from both the Grabouw production areas stored at CA 1.5% O₂+1% CO₂ were of the best post storage quality after a storage period of 4 and 6 months and a simulated shipment period of 4 w RA at -0.5°C followed by a shelf life period of up to 7 d at 20°C. Superficial scald incidence was significantly lower on fruit stored at RA and CA 6% O₂+0% CO₂ than on fruit stored at CA 1.5% O₂+0% CO₂, CA 1.5% O₂+1% CO₂.  Storage of fruit at high O₂ concentrations, 6-8% O₂+0%CO₂ showed best results for inhibiting superficial or soft scald, but fruit were significantly more yellow than fruit stored at lower O₂ concentrations (1.5% O₂+0-1% CO₂)
• Seasonal variation occurred as far as fruit quality is concerned.

Recommendations:

The project should be extended for one additional season to confirm the CA 1.5%O₂ +0%CO₂ and the CA 6% O₂ +0% CO₂ storage results.  Currently CA conditions of 1.5%O₂ +<1%CO₂ can be recommended for storage of Abate Fetel pears.