The 2010 ASHS Annual Conference

Two experiments were conducted to identify volatile compounds during ripening of 'Simmonds' avocado (Persea americana Mill.) and how the volatile composition is affected by exogenous ethylene and 1-methylcyclopropene (MCP) treatments. For Experiment 1, treatments were: C1 - non-treated control; E24 – exogenous ethylene for 24 h at 20 °C; MCP – immersion in aqueous formulation of 1-MCP at 150 µg.L^-1 a.i. for 1 min at 20 °C. In Experiment 2, treatments were: C2 - non-treated control; E12 – exogenous ethylene for 12 h, E12+MCP – exogenous ethylene for 12 h + 12 h air + aqueous 1-MCP at 150 µg.L^-1 a.i. for 1 min. Treatments were applied to mature-green fruit 24 h after harvest and fruit ripening was monitored at 20 °C. Respiration and ethylene production rates were measured daily, while whole fruit firmness was determined every other day. Fruit were considered commercially ripe upon reaching 10 to 15 N firmness at the equator (5-cm dia. flat-plate probe at 2.5 mm deformation). Fruit were assessed for volatile analysis at mature-green, mid-ripe (half of initial fruit firmness) and ripe maturity stages. Volatiles were collected for 1 h from 100 g of diced pulp using a purge-and-trap system and compounds were identified by GC-MS. In Experiment 1, C1-fruit ripened within 7 d. Treatment E24 hastened the onset of the ethylene climacteric peak by 1 d and ripening by 2 d, while MCP delayed both by 2 d. In Experiment 2, C2-fruit ripened in 6 d. Treatment E12 did not hasten the climacteric nor ripening, but E12+MCP delayed both by 2 d. Total volatiles decreased during ripening, most markedly from mid-ripe to ripe stage. The main group of volatiles identified was sesquiterpenes, predominant in mature-green and mid-ripe stages; β-caryophyllene, α-copaene and β-cubebene were the most abundant compounds. Hexanal was also a great contributor to total volatiles. Only a few compounds were detected in ripe fruit; alcohols and aldehydes were predominant and several sesquiterpenes were not detected. Reduced amounts of several compounds and total volatiles were found for MCP-treated fruit when assessed at mid-ripe maturity stage. However, application of exogenous ethylene or 1-MCP did not affect total volatiles in ripe fruit. The additional benefit of shelf-life extension promoted by aqueous 1-MCP treatments corroborates the potential use as a postharvest treatment for the fast-ripening West Indian ‘Simmonds’ avocado.