So, does it bruise the fruit?
Fruit handled by a mobile harvesting system had an acceptable level of damage, preliminary tests showed.
The Picker Tech harvester is on tracks, making it easy to turn and reducing soil compaction.
A concern about mechanically assisted harvesting of fresh apples has been the amount of bruising that might be caused by the machine.
Dr. Ines Hanrahan, project manager with the Washington Tree Fruit Research Commission, conducted preliminary tests with the Oxbo mobile harvesting system last season and concluded that fruit damage was within acceptable levels.
The machine was developed by Picker Technologies. Hanrahan did the tests at the company’s machine shop in Bellevue, Washington, using Golden Delicious, a variety that is particularly sensitive to bruising.
The machine has four transport tubes into which workers place apples picked from the trees. The apples are carried up the tubes and into a decelerator tank before moving into an electronic sorter and through a dry bin filler into the bin.
Only one of the machine’s four transport tubes was used for the experiments. As the tests were done in May, the apples had been stored in controlled atmosphere and treated with MCP (1-methylcyclopropene). Sizes were mixed, averaging 88, and average fruit firmness was estimated at 15.1 pounds. The apples were all considered Washington Extra Fancy grade and were free of bruising and puncture wounds before they went into the machine.
To test the effects of the full machine, apples were fed into the tube at a rate of 50 apples per minute. The harvester graded the fruit as 88.4 percent Washington Extra Fancy and 5.6 percent U.S. Extra Fancy.
Forty-four percent of the fruit had no defects after going through the machine. Another 44 percent had minor defects that would not cause downgrading from Washington Extra Fancy and 5.6 percent were downgraded to U.S. Extra Fancy because of stem abrasions or scratches. The rest of the fruit was downgraded to cull because of stem punctures or impact bruises more than 3/4-inch long.
Hanrahan concluded that fruit classified as U.S. Extra Fancy could blend in with the Washington Extra Fancy because none of the defects were severe enough to affect the appearance of the pack and a 10 percent tolerance level for out-of-grade fruit is typically allowed.
Hanrahan and the Picker Technologies employees thought the long impact bruises were most likely caused by a sharp edge on the cups of the bin filler and believe modifications done since the tests have addressed that.
The stem punctures, and possibly some of the stem abrasions and small scratches, were likely caused primarily by the transport cups between the decelerator and grader. Picker Technologies believes this problem will be eliminated in the commercial version, which will have different cups.
Hanrahan also did experiments with just the transport tube and decelerator. Of the fruit run through those sections of the machine, no fruit were classified as culls and 3.5 percent were downgraded to U.S. Extra Fancy.
“We think this part of the machine works well,” she reported.
To test the dry bin filler alone, Hanrahan placed apples on the conveyor belt going into the filler at a rate of 50 apples per minute and collected samples from the bin. Ninety-seven percent of the fruit were afterwards classified as Washington Extra Fancy. The modifications to the bin filler cups should result in less fruit damage, she said.
John Albert, vice president of business development for Picker Technologies, said this fall that the company’s goal in terms of bruising was to damage no more fruit than with traditional picking. “Our whole objective from day one was that machine harvesting, at its worst, should be no worse than hand harvesting, and we believe we’re better.”
Hanrahan was conducting field tests this fall to determine the picking efficiency of workers with the machine; the effectiveness of in-field cull sorting; the extent of bruising caused by the bin filler; and the quality of the fruit after storage. Tests were done on Gala, Fuji, Red Delicious, Golden Delicious, and Granny Smith.