Effects of aminoethoxyvinylglycine plus 1-methylcyclopropene on 'Royal Gala' apple volatile production after cold storage

Abstract

Both aminoethoxyvinylglycine (AVG) and 1-methylcyclopropene (1-MCP) are useful tools for managing apple fruit ripening, and their impacts on apple volatile production have been independently assessed. In this work, their combined effect, as might occur in commercial production and postharvest storage, on 'Royal Gala' apple volatile production at harvest and after air storage was compared with the effect of each alone. An aqueous solution of AVG was applied to 'Royal Gala' apple trees 4 weeks before the normal harvest date (H1) at 124 g ha-1/a.i. in 2004 and 2005. Control and AVG-treated fruit were treated at H1 or after harvest of AVG fruit 2 weeks later (H2) for 20 h at 30 °C with 1-MCP at a final headspace concentration of 1 μL L-1. Fruit were ripened for 7 d at room temperature immediately after harvest and treatment or after treatment and then cold storage at 4 °C for 6 or 12 weeks. Peel and cortex tissue of control and AVG plus 1-MCP-treated fruit was provided with butanol or hexanol and ester production was quantified. The combination of AVG plus 1-MCP was more effective in reducing internal ethylene concentration than either alone. Both total volatile production and that of the major individual esters, including hexyl acetate, butyl acetate, and 2-methylbutylacetate, which are considered key constituents of 'Gala' aroma, were consistently repressed by the combination of AVG plus 1-MCP after harvest and up to 12 weeks of cold storage. The effects of AVG plus 1-MCP were evident even with H2 fruit when the effects of AVG alone on fruit ripening were at least partially lost. Because alcohol-acyl transferase activity was unaffected by AVG plus 1-MCP, AVG plus 1-MCP-treated peel and cortex samples had similar total ester production when they were provided butanol or hexanol. Total alcohols showed recovery in most treatments except AVG plus 1-MCP, so precursor availability was likely the major factor limiting ester production. The results indicated a sustained adverse effect of the AVG plus 1-MCP treatment on aroma volatile production that could impact consumer acceptability.