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ARS Home » Pacific West Area » Wenatchee, Washington » Physiology and Pathology of Tree Fruits Research » Research » Publications at this Location » Publication #250828

Title: Harvesting by Peel Color to Reduce Bruising of "Golden Delicious" Apples

item MITSUHASHI-GONZALEZ, KAY - Washington State University
item Curry, Eric
item FELLMAN, JOHN - Washington State University
item PITTS, MARVIN - Washington State University
item CLARA, CARTER - Washington State University

Submitted to: International Journal of Fruit Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/7/2010
Publication Date: 6/8/2010
Citation: Mitsuhashi-Gonzalez, K., Curry, E.A., Fellman, J.K., Pitts, M.J., Clara, C.D. 2010. Harvesting by Peel Color to Reduce Bruising of "Golden Delicious" Apples. Journal Tree Fruit Production. 10(2):166-176.

Interpretive Summary: ‘Golden Delicious’ apples are usually harvested in a single pick depending on peel ground (background) color, compared to other cultivars such as ‘Gala’ that are harvested more than once based on development of red pigmentation as well as changing ground color. ‘Golden Delicious’ apples are harvested approximately 130 days after full bloom at which time peel color is transitioning from green (less mature) to yellow (more mature), and fruit firmness is gradually decreasing. The objective of this research was to determine if apple bruising at harvest was more closely related to changing peel color or fruit firmness for possible use as a predictive tool. This study was completed over two harvests (2007-2008) in a commercial organic apple orchard. Sixty fruit were harvested at each peel color stage (green, white and yellow). Fruit were transported to the laboratory and left at 22 °C for 48 hours to establish temperature equilibrium. To simulate bruising by a picker, a silicon finger was attached to an Instron universal materials testing instrument and a force applied to each fruit. Bruise volume was measured and calculated in cubic millimeters. Flesh firmness was also measured on each fruit. Analysis of these data suggest 1) peel color is a better indicator of bruise susceptibility than fruit flesh firmness; 2) severity of picker-induced bruising in ‘Golden Delicious’ might be reduced by picking apples while they are green; and 3) although green apples bruised less than white and yellow apples at constant depth (as imposed by the silicon finger), they are also more firmly attached to the tree and one must exert a greater force to remove them. Thus, proper technique is key to minimizing picker-induced bruising.

Technical Abstract: ‘Golden Delicious’ apples harvested at three peel color stages were immediately bruised to a constant depth using an artificial finger attached to an Instron universal material testing instrument. Bruised tissue was sliced sequentially from the fruit surface in a plane perpendicular to the direction of the applied force until discoloration was no longer evident. Discolored area was measured on each tissue slice using a digital caliper. Analysis showed there was a significant difference in bruise volume between green and yellow peel stages, whereas susceptibility to bruising of fruit at the white (intermediary) stage appeared to vary with environmental condition (year to year). Compared with the previous year, 2008 growing season was cooler and shorter and bruise volume at all stages was greater. Analysis of fruit maturity suggested bruise volume was influenced by ripening-induced changes in cell structure, size and integrity. Where fruit peel color changed but firmness did not, bruise volume increased. We conclude that peel color is a better indicator of bruise susceptibility than fruit flesh firmness.