The Effects of ReTain, Harvista, and NAA on the Quality of 'Mcintosh' Apples

It is recommended that fruit treated with NAA (naphthalene acetic acid) not be treated with SmartFresh^TM (postharvest 1-MCP) because the former stimulates ethylene production.  If fruit have already been treated with ReTain, it may be all right since the stimulation of ethylene production would be prevented.  ReTain was sprayed 2 weeks prior to harvest, Harvista 1 week prior to harvest and NAA 3 days prior to harvest.  In one year, there were 2 harvests of ‘McIntosh’, the second harvest 3 days after the first.  In the second year, there was only one harvest.  SmartFresh^TMwas applied to half the harvested fruit.  In the second year, it was applied either on day 1 or delayed until day 5. In both years, the internal ethylene concentration (IEC) was higher, firmness lower and the starch index higher for untreated and NAA treated fruit.   ReTain and ReTain + NAA treated fruit were similar to Harvista treated fruit for these assessments.  After 8 months of controlled atmosphere (CA) storage, untreated and NAA treated fruit had the lowest firmness while Harvista treated fruit were the most firm.  Use of SmartFresh^TM made the ReTain and the ReTain + NAA fruit as firm as the Harvista fruit while the NAA treated fruit were softest.  Delaying the  SmartFresh^TM treatment until day 5 lowered the firmness in all fruit except those treated with Harvista.  In the first year, harvest 2 had higher levels of flesh browning than harvest 1 and the use of SmartFresh^TM lowered the flesh browning, although not by much for the NAA treated fruit.  External carbon dioxide injury was generally worst in ReTain and ReTain + NAA treated fruit and tended to be worse with SmartFresh^TM use.  There were low levels of senescent breakdown, mainly in harvest 1 NAA treated fruit and ReTain treated fruit without SmartFresh^TM.  Low levels of core browning were present, but lowest with Harvista.  In the second year, Harvista without SmartFresh^TM had the highest level of external carbon dioxide injury and this was reduced with  SmartFresh^TM use.  Untreated, ReTain and ReTain + NAA treated fruit all showed higher levels of external carbon dioxide injury when SmartFresh^TM was used.  Combining ReTain with NAA resulted in fruit that behaved similarly to fruit treated with ReTain only.