Report to the Industry on Fruit Quality and Packing Practices for Washington Grown Apples
Project Goals and Methodology
This information comes from a report on fruit quality and packing practices for Red Delicious, Golden Delicious, Gala, and Fuji apples sampled during the 1989-1992 seasons. The project was funded by the Washington Tree Fruit Research Commission. A portion of the work on Golden Delicious was funded by the Washington Apple Commission. The cooperation of numerous packinghouse managers and personnel is acknowledged.
A primary goal of this project is to help the industry learn about the quality of apples shipped from Washington and how packing practices affect fruit quality. Warehouse managers need to learn how their fruit and packing practices compare with those of other packinghouses.
Technicians sampled fruit from every participating packingline actively packing during weekly visits. The fruit were sampled from just before dumping to just prior to being put into the box.
The technician recorded the temperature of the apples at various stages in the packing process while in the packinghouse as well as the temperatures of the water and the dryer air. Temperatures were taken using an electronic thermometer with a needle probe. Water temperatures were taken by dipping the probe into the water at various locations in the tank. Fruit temperatures are an average of five apples with the probe inserted 0.5 inch into the flesh. Dryer temperatures were read off the gauges at the side of the dryer. Chemicals applied were noted.
The technician brought the samples back to the laboratory in Wenatchee. The apples' firmness, soluble solids, and acidity were tested. Fruit were also examined for internal and external disorders. During the early part of the season, fruit were also rated for starch clearing.
Twenty fruit were sampled from the packingline at each visit. Ten fruit were examined the day after collection and another 10 were held at room temperature (70°F) for 7 days and tested.
This information can be considered in light of differences in fruit quality by variety, variety by year, packing practices by variety, packing practices by packinghouse, and/or by grower lot. It is also useful to compare the four varieties.
Fruit Quality by Variety
Obviously there are differences in the characteristics of apples of different varieties. This study considered the quality of fruit sampled on the packingline as well as after being held for 7 days at 70°F. The following table illustrates the comparative quality characteristics of each variety. These data reflect the quality characteristics regardless of date of sampling, storage regime, or year.
|Variety||Firmness at time of packing (lbs.)||Firmness after 7 days at 70°F (lbs.)||Soluble solids (%)||Acidity (%)||Sugar/acid ratio|
Storage type affects fruit quality. The study demonstrates the importance of CA over regular storage to retain crispness, even when the storage period is short. This is illustrated in the next table in which short-term CA-stored fruit is compared with fruit from regular storage sampled the same week. These data are from commercial samples of "special storage" compared with those from regular storage packed during the first 90 days after harvest.
|Red Delicious||14.2 lbs.||14.8 lbs.|
Temperature management also affects fruit quality. Heating fruit in a dump tank to clean it and get a better shine can be detrimental to fruit quality if the apple is not cooled during or immediately after the packing process. The following table compares temperatures at various points in the packing process.
The average packing (tray-filling) temperatures were higher than desirable to maintain fruit quality. Further studies indicate that fruit firmness is rapidly lost when heat is not removed. Contained in the body of this report are the results of studies on the decline in fruit firmness when held at different temperatures. For example, when Red Delicious are held at 60°F for 14 days they will lose an average of 2.3 lbs., as compared with a loss of 0.6 lb. when held at 32°F. More work will be done to determine the actual rate of cooling of fruit in packed boxes under commercial conditions.
|Variety||Starting temperature*||Dump tank water temperature**||Packing temperature***|
|* Fruit temperature in
bin prior to dumping.|
**Water temperature in dump tank.
***Fruit temperature (0.5' under skin) at tray filler.
Annual Variation in Fruit Quality
It has been a pleasure working on this project. I express appreciation to the Washington Tree Fruit Research Commission, packers and, most of all, to Ken Miller, Lori Kutch, and Casey Parish for their efforts. I hope this information is of help to you in improving your understanding and points the way toward better fruit quality upon arrival. If you have comments or wish to discuss this information, feel free to give me a call.
Dr. Eugene Kupferman, Postharvest Specialist
WSU Tree Fruit Research and Extension Center
1100 N. Western Ave., Wenatchee, WA 98801
Tree Fruit Postharvest Journal 5(2):3-4