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Harvest Maturity Affects Storability of ‘Ambrosia’ Apples

As part of a larger project, ‘Ambrosia’ apple maturity was again monitored during the 2007 harvest season. Fruit maturity was evaluated on 10-apple samples twice a week from two commercial orchards in the Simcoe area of Ontario. 

Similar to the results in year 1 of this study, ‘Ambrosia’ apples produced very little ethylene during maturation on the tree (Table 1). As the starch degraded and color changed, there continued to be only trace amounts of internal ethylene present (<1 ppm). This makes IEC a difficult indicator of fruit maturity for ’Ambrosia’, but at the same time makes ‘Ambrosia’ an ideal candidate for postharvest SmartFresh (1-MCP) treatment. 

¹ Values are the average of 10 apples
² BC ‘Ambrosia’ color chart
³ BC ‘Ambrosia’ starch chart
⁴ Harvest for the storage experiments

Sample of 50 apples were also harvested from each orchard during each week of maturity evaluation, starting on Sept. 21^st. These fruit were held in air storage at 0.5^oC for 4 months and then evaluated for quality during 14 days at 21^oC, to determine the effect of harvest maturity on storability.

Overall, harvest time significantly affected (P<0.01) firmness, internal ethylene concentration (IEC), acidity, and greasiness of ‘Ambrosia’ apples after 4 months of storage in air at 0.5^oC. ‘Ambrosia’ fruit harvested on Sept. 28^th or before were less greasy after storage than those harvested on Oct. 5^th or after. In Orchard 2, apples harvested on Sept. 28^th or before were firmer than those harvested on Oct. 5^th or after (2+ lb difference). This effect was also observed in fruit from Orchard 1, but only after 14 days at 21^oC.

The above storage trends suggest that optimum harvest should have been somewhere between Sept. 28^th and Oct. 5^th in 2007. In Orchard 1, there was a notable increase in yellow color, fruit softening, starch index values, and IEC during this time. These changes were more subtle in Orchard 2, as the variation in fruit maturity was greater, which was likely due to orchard management and more canopy growth.

Trends in apple maturity can vary enormously year-to-year. Therefore, these evaluations need to be continued for additional growing seasons before confident conclusions can be made.mMore data and replication is needed in order to reduce the large variations and standard error.

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