Effects of Pre-Harvest Hexanal and Post-Harvest 1-Methylcyclopropene Treatments on Bitter Pit Incidence and Fruit Quality in ‘Arisoo’ Apples

This study evaluated the effects of pre-harvest hexanal and post-harvest 1-methylcyclopropene (1-MCP) treatments on bitter pit incidence and fruit quality in ‘Arisoo’ apples during cold storage. Hexanal (0.02%) was sprayed on trees twice, 18 and 8 days before harvest, and 1-MCP (1 μL·L−1) was applied by fumigation immediately after harvest. Treated apples were subsequently stored at 0.5 ± 1 °C for 5 months. At harvest, the control group showed an incidence rate of 20.6% and a severity score of 0.34, while the hexanal-treated group had a reduced incidence of 13.2% and a severity score of 0.18. Fruit quality parameters did not differ significantly between the control and hexanal-treated groups at harvest. During cold storage, spot incidence significantly increased in the control after 2 months and reached 60.5% after 5 months. In contrast, bitter pit incidence in the hexanal and 1-MCP-treated groups was lower after 5 months, at 46.6% and 47.1%, respectively. No significant difference in spot severity was observed between the hexanal and 1-MCP treatments. Polyphenol oxidase activity increased in all treatments during storage, but both hexanal and 1-MCP significantly inhibited this increase compared to the control. Total sugar and uronic acid contents decreased across all treatments during storage. However, the hexanal and 1-MCP treatments mitigated this reduction relative to the control. At the end of storage, apples treated with 1-MCP had lower internal ethylene concentrations and higher flesh firmness compared to both the control and hexanal-treated apples. In conclusion, pre-harvest hexanal application reduced the bitter pit incidence at harvest and during storage, while post-harvest 1-MCP provided a similar reduction effect and better preserved fruit quality during cold storage.