Influence of ethylene inhibition by 1-methylcyclopropene on apricot quality, volatile production, and glycosidase activity of low- and high-aroma varieties of apricots

Apricots of two varieties, Ceccona with strong aroma and San Castrese with low aroma but good firmness, were treated with 1 muL L-1 1-methylcyclopropene (1-MCP) for 12 h at 20 degreesC and then kept for shelf life at 20 degreesC and 85% relative humidity. 1 -MCP treatment strongly inhibited ethylene production in apricots of both varieties, and softening was delayed. Fruit softening started before the rise of ethylene in air-treated apricots, which softened even when the rise of ethylene production was inhibited by 1 -MCP. The softening reduction was more significant in Ceccona apricots than in San Castrese. Pectinmethylesterase (PME) activity declined in Ceccona fruit regardless of the treatment; in San Castrese, PME of air-treated fruit slightly increased, whereas in 1-MCP-treated apricots the activity declined. alpha-D-Galactosidase (alpha-gal) and beta-D-galactosidase (beta-gal) activities in Ceccona apricot were significantly reduced by 1 -MCP treatment, whereas in San Castrese apricot no difference in activities was observed between air- and 1-MCP-treated fruit. The pattern Of beta-D-Xylosidase (xyl) activity in San Castrese apricot was similar to that of beta-gal, showing a peak on day 4 without difference between treatments. (X-D-Mannosidase (a-man) activity of air-treated apricots of both varieties rose slightly, and 1-MCP treatment decreased the enzyme activity in both varieties. alpha-D-Glucosidase (alpha-glu) decreased in air-treated apricots in both varieties, and 1 -MCP maintained higher activity in Ceccona fruit but not in San Castrese. Acidity decreased during postharvest ripening regardless of the treatment, whereas soluble solids content (SSC) increased in Ceccona apricot and slightly diminished in San Castrese ones without any effect by 1-MCP treatment. 1-MCP did not show any effect on apricot color; in contrast, it affected the volatiles profile, especially in Ceccona apricot, reducing the synthesis of lactones and promoting the rise of terpenols.