Preconditioning at the Shipping Point
Ethylene preconditioning treatment, typically performed at the shipping point, is only effective when conducted on kiwifruit that is recently harvested. It is also effective on kiwifruit that has been in cold storage for less than 5 weeks. Fruits kept in cold storage for longer than 5 weeks will produce their own ethylene and ripen upon transfer to ripening temperatures of 15-21°C (59-70°F).
Apply 100 ppm ethylene for a minimum of 12 hours during the initial phase of the ripening cycle.
The temperature during ethylene application and shipment should be adjusted according to the anticipated consumption schedule:
Rate of kiwifruit softening after ethylene application at 20°C (68°F):
To prevent softening due to delayed shipments, apply ethylene to cold kiwifruit. Cold kiwifruit treated at near 0°C (32°F) and maintained at that temperature may be held up to 5 weeks. These kiwifruit will reach a firmness of about 3 pounds in 2 to 3 days after being transferred to 20°C (68°F). High relative humidity is recommended: 90-95%
When ethylene application is complete, vent ripening room thoroughly by opening the doors to remove excess ethylene and carbon dioxide that builds up during the ripening process.
For delayed ripening, transport preconditioned kiwi near 0°C (32°F).
Ripening at a Distribution Point
Firmness tests should be performed on incoming kiwifruit. As a general rule, kiwi that have a flesh firmness level of 8- 10 pounds or greater should be ripened by using ethylene at warm temperature. Fruit that has been in storage equal to or longer than 4 weeks or have a flesh firmness of less than 8 pounds can be ripened close to “ready to eat” by temperature management only.
In all the cases, temperature conditions for kiwifruit during storage treatment should be adjusted according to a shipment schedule to stores / customers. When held at 20°C (68°F), kiwi will soften at about 2 pounds per day, and this is slowed by lower temperatures.
Unless they will be consumed within three days, keep kiwi at temperatures below 7.5°C (45°F).
Some parts of this article are adapted from:
Crisosto, Carlos H. Optimum Procedures for Ripening Kiwifruit. http://kare.ucanr.edu/files/123835.pdf
For more information on Kiwi and other fruits, please visit the web site of UC Davis.
A great resource for any Fruit Ripener is a publication from UC Davis entitled “Fruit Ripening & Ethylene Management”. Click here for more information.
For ethylene generators, visit Catalytic Generators.
Information on this site is amassed from a diverse number of sources. While we have made great effort to provide accurate and current ripening techniques, we make no warranties regarding these recommendations or the applicability of such information to a particular ripening operation. Please note that we do not provide these recommendations as a replacement for technical ripening experts; if having ripening problems or starting a ripening program, we suggest that professionals be consulted.