Storage regimes to allow softening in a processing apple treated with 1-methylcyclopropene

Abstract

The objective of this study was to investigate the effects of storage regime and postharvest 1-methylcyclopropene (1-MCP) treatment timing on softening of ‘Northern Spy’ apples, to determine if ideal firmness for processing could be achieved after storage while at the same time maintaining fruit quality and extending storage life. Over 4 yr of study, ‘Northern Spy’ apples with or without 1-MCP (1 μL L−1) were held for up to 12.5 mo at 0 °C–1 °C in the following regimes: (1) controlled atmosphere (CA) with or without 2 wk post-storage ambient air; (2) ambient air or CA; (3) CA with up to 6 mo delayed 1-MCP treatment; (4) delayed CA establishment for up to 4 mo; (5) delayed 1-MCP treatment in combination with delayed CA establishment for 1 or 2 mo. 1-MCP treatment at harvest consistently enhanced firmness retention, which remained too high for processing. Delayed 1-MCP treatment allowed more firmness loss but fruit remained firmer than those not treated, and these apples would be acceptable for subsequent processing (∼67–72 N). 1-MCP-treated fruit developed higher incidence of core browning than those not treated, especially after 6 mo of storage. However, this is not a major problem for processing because core tissue is removed. Delayed CA within any regime did not result in apples with firmness values acceptable for processing, while additional air storage for 2 wk at 0 °C after CA had no significant effect. Overall, delayed 1-MCP treatment with no delay in CA provided the most acceptable apple firmness for processing.