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Storage

The Washington apple industry uses regular cold storage for short-term storage, and Controlled Atmosphere (CA) storage for longer storage. Regular cold storage is used for most of the fruit marketed in the fall and early winter. Controlled atmosphere storage technology makes buying apples all year possible, because the ripening process is slowed down further. CA rooms are sealed, airtight, refrigerated rooms in the warehouse in which the levels of oxygen are reduced to 1-2%, and temperatures are maintained at 32-36° F. Humidity is regulated at 95%, and carbon dioxide levels are also controlled.  Most apples are stored before being sorted and packed for market.
 

Apple

Apples are placed in cold storage when they arrive at the packinghouse from the farm so that field heat can be removed as quickly as possible.  Rapid removal of field heat has positive effects on both fruit quality and reduction in storage decay.  Apples continue to breathe after they are picked from the tree, so postharvest cooling slows respiration and increases storage life.  Apples take in oxygen and give off carbon dioxide while starches change to sugar in the fruit flesh (ripening).

Apple varieties differ in their conditions needed for proper storage. Researchers develop specific recommendations to preserve good fruit quality and extend storage life of fruit.  For example, the Honeycrisp variety is unique, in that higher starch levels than other varieties are considered acceptable in storage.  Honeycrisp tend to require a preconditioning period before being put into regular cold or CA storage, generally being held at 50° F for 5-7 days before storage.

Practices before and after harvest affect disease and decay in postharvest apples, and how well they will store.  Things that can be done in the orchard: apply a late season fungicide to decrease pathogen levels that come to the packinghouse from the orchard. Fungicides need to be rotated to prevent resistance though. Orchard sanitation is important, pruning out dead branches and cankers where fungi live; good nutrition will improve fruit quality; harvesting at the correct maturity level; and cleaning bins to remove pathogens from soil and debris.  In the packinghouse: Sanitation is imperative. Sanitizing rooms, packing lines, surfaces and equipment will kill fungal spores that cause decay in fruit.

Useful References and Resources:

More information specific to handling and storage of apples can be found using the links below. Additional resources can be located using the search box at the top of this page.

Pear

Pears are harvested mature but not yet ripe, and require a chilling time in cold storage in order to ripen properly at room temperature. Different pear varieties have specific handling and storage regimes, depending on the desired length of storage time needed, and the maturity of the fruit at harvest. The goal is to have fruit that will ripen a few days after consumers purchase them at the market, with excellent fruit quality for eating. Ripening pears is a complex process. Fruit are placed in cold storage immediately after harvest to stop the ripening process, so that fruit can be stored long-term, and available for market on specific dates. The cold temperatures and controlled atmosphere (CA) storage stop the natural ripening process, which inhibits ethylene, a ripening hormone. In order for pears to start the ripening process again, at the proper time for marketing, they need to remain at cold temperatures for a specific amount of time (“chilling requirement”), with or without ripening treatments such as addition of ethylene, and then “conditioned” at warmer temperatures before packing and shipping. There have been challenges in storing winter pears long-term due to their ripening processes and susceptibility to fungal storage rots. Currently scientists at Washington State University (WSU) in cooperation with researchers at Oregon State University (OSU) are studying ripening compounds to use for improved fruit quality. (learn more) For more information related to pear handling and conditioning refer to the USA Pear Handling Manual (conditioning begins on page 21).

Useful Resources and References:

More information specific to handling and storage of pears can be found using the links below. Additional resources can be located using the search box at the top of this page.

WSU Resources

 

Industry Resources

 

WTFRC Research Reports:   

 

Trade Articles on Pear Storage:

 

Cherry

Sweet cherries are harvested at full ripeness and at their highest quality. This means that the fruit need to be cooled as soon as possible after harvest to slow down the respiration process, which in turn slows down the aging process degrading quality. Cherries do not have reserve carbohydrates like starch in apples, but it is possible to store them for a few months, depending on their condition when they arrive at the packinghouse. Cherries are not able to prevent water loss very well, so they need to be stored in an environment with temperature and relative humidity monitored closely to minimize movement of water from inside the fruit to the air.

You can find more information on cherries, and postharvest handling and storage of cherries, please visit the WSU-TFREC Postharvest Information Network.

Useful Resources and References:

More information specific to handling and storage of cherries can be found using the links below. Additional resources can be located using the search box at the top of this page.

WSU-TFREC Postharvest Information Network

 

WTFRC Research Reports

 

Other University References on Cherry Handling and Storage

 

Trade Articles 

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