The 2012 ASHS Annual Conference

The SmartFresh label was revised in 2009 to allow for more than one application of 1-methylcyclopropene (1-MCP) to fruit.  To simulate the time taken to fill a controlled atmosphere (CA) room over a 7 day period prior to establishment of the storage atmosphere,  ‘McIntosh’ fruit were harvested 3 times in one week.  The second and third harvests were 3 and 7 days after harvest 1.  At each harvest, fruit were cooled overnight and then 1-MCP applied the following day.  Fruit from earlier harvests were treated again or for the first time when each successive harvest was treated.   Internal ethylene concentration (IEC) was higher in fruit that were held in storage for longer periods before 1-MCP treatment but was kept low with multiple treatments.  CA conditions were established after the last 1-MCP treatment and fruit were stored for 8 months.  1-MCP treated ‘McIntosh’ from harvest 1 were more firm after storage, but no firmer than untreated fruit if treatment was delayed until day 8.  Delaying 1-MCP treatment for harvest 2 until day 4 resulted in lower firmness than treatment on the day after harvest.  For harvests 1 and 2, carbon dioxide injury after storage was more prevalent if 1-MCP treatment was soon after harvest.  Untreated fruit from all harvests and harvest 3 treated on day 1 showed no evidence of carbon dioxide injury.  Senescent breakdown at the end of the storage period was greatest in untreated fruit and when 1-MCP treatment was delayed.  Rapid 1-MCP treatment is important to maintain firmness of  ‘McIntosh’, but  early and multiple 1-MCP treatments exacerbate carbon dioxide injury if fruit are not treated with diphenylamine (DPA).