1-MCP Concentration and Timing of Application Alters the Ripening of ‘McIntosh’ Apples during Storage

This study evaluated the effects of 1-methylcyclopropene (1-MCP; SmartFresh^SM) concentration (1000 vs. 625 ppb) and treatment delays (3, 7, and 10 days after harvest) on the ripening and incidence of storage disorders in ‘McIntosh’ apples from three harvest times. Apples were stored in air at 0-1^oC for 3 and 6 months or in controlled atmosphere (CA) storage at 3^oC for 6 and 9 months. 

Apples treated with 1-MCP and held in air or CA storage were firmer than those not treated, but this difference in firmness was less with later harvests, more delay before 1-MCP treatment, and longer storage time. Apples treated with 1000 ppb 1-MCP were often firmer than those treated with 625 ppb after 6 months of storage and/or 7 d at 22^oC. These results show the importance of 1-MCP concentration and time between harvest and application. Since a specific amount of 1-MCP is utilized for a range of commercial room sizes (SmartFresh^SM application by AgroFresh Inc.), in certain commercial situations the concentration of 1-MCP can be less than the expected 1000 ppb and for cultivars like ‘McIntosh’ this can reduce the beneficial effect on firmness. The SmartFresh^SM label in Canada states that application must be made within 3 days of harvest, whereas the window for treatment in the USA is 7 days. Firmness retention in ‘McIntosh’ apples due to 1-MCP would be better with application closer to harvest, as indicated by the results of this study.

Ethylene and respiration were reduced in apples treated with 1-MCP, especially in fruit from the first harvest and those treated 3 days after harvest. Fruit treated with 1000 ppb 1-MCP showed a slower increase in ethylene production than those treated with 625 ppb during 14 days at 22^oC after storage. Storage disorders were most prevalent in ‘McIntosh’ apples stored for 6 months in air at 0-1^oC, while fruit from the first harvest treated with 1-MCP 3 days after harvest developed the fewest disorders. 1-MCP reduced the incidence of superficial scald, flesh browning, core browning, and senescent breakdown, while 1-MCP concentration and treatment delay had varying effects.

The research described here has provided the basis for the Canadian SmartFresh^SM label and the recommendation by AgroFresh Inc. that ‘McIntosh’ apples should be treated within 3 days of harvest. The importance of minimizing 1-MCP treatment delays becomes greater as storage time increases and apples are pushed to their maximum life span. 1-MCP concentrations less than 1000 ppb due to application methods can also reduce the beneficial effects in ‘McIntosh’ fruit, especially with treatment delays or long-term storage periods. Therefore, storage operators should take care as to when and how their apples are treated with 1-MCP. 

Anyone wanting the complete scientific paper (in HortTechnology, 2008) can contact the author at Jennifer.DeEll@ontario.ca

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