Combined application of ethylene and 1-methylcyclopropene on ripening and volatile compound production of 'Golden' papaya

Papaya (Carica papaya L.) fruit are consumed worldwide, but they are highly perishable. The effects of the application of 1-methylcyclopropene (1-MCP) with and without ethylene on 'Golden' papaya ripening and production of volatile compounds responsible for aroma. Fruit were treated with 2.5 mu l L(-1 )ethylene and/or 100 nL L-1 of 1-MCP for 12h as follows: I) control, II) ethylene, III) 1-MCP, IV) ethylene + 1-MCP (simultaneous), V) ethylene followed by application of 1-MCP at a 12 h interval and VI) ethylene + 1-MCP without any interval. Pulp firmness, skin color, skin chlorophyll content, skin and pulp carotenoids, ethylene production, respiratory activity, internal ethylene concentration (IEC), pectin methyl esterase (PME) activity, 1-carboxylic acid-1 -aminocyclopropane oxidase (ACC oxidase) activity and volatile compounds were measured. Fruit were stored at 22 degrees C, with analysis of volatile compounds performed until day 8 and all others until day 6. Fruit treated with only 1-MCP developed rubberized pulp. Fruit treated simultaneously with ethylene and 1-MCP reached desirable firmness for consumption by day 6. Co-application of 1-MCP + ethylene promoted chlorophyll degradation. A consistent increase in ethylene production in 1-MCP-treated fruit above those observed in control fruit and in fruit treated with ethylene only was observed. In relation to volatile compounds, linalool and its oxides were affected less by 1-MCP treatment, with or without ethylene, on days 2 and 6, and did not affect fruit flavor.