372 1-MCP-mediated Ripening Changes in `McIntosh' Apples

Abstract

`McIntosh' apples were treated at 20 °C with 0.0, 0.01, 0.1, 1.0, 10, and 100 ppm 1-methylcyclopropene (1-MCP; EthylBloc™) a day after harvest for 18 h and stored at 0 °C in air. Apples were also continuously exposed to 0.0 and 25 ppm 1-MCP under controlled atmosphere (CA; 0 °C in 4.5 kPa CO2 and 3 kPa O2) by re-establishing the initial concentration at week 9 and 17. The threshold concentration of 1-MCP at 20 °C to inhibit de novo ethylene production in apple fruit was determined to be 1.0 ppm. Interestingly, the ethylene antagonist completely inhibited (99.67%) ethylene production in apples, which were removed from 0 °C in air and CA after 9 weeks and held at 20 °C up to 6 days. Overall, ethylene production was 10- to 100-fold less in apples treated with 1 ppm and above 1-MCP than in untreated apples. 1-MCP-treated apples showed less softening; fruit firmness was 2-4 Lb higher compared to untreated apples. Total soluble solids of apples was not affected by 1-MCP treatment. Total hydrophobic volatiles, including the sesquiterpene hydrocarbon α-farnesene, from apples measured by SPME/GC showed an inverse relation to 1-MCP concentration. Contents of α-farnesene and its putative superficial scald-causing catabolite, conjugated triene alcohol, in the skin were reduced 60% to 90% by 1-MCP. However, 1-MCP did not suppress the incidence of scald or other disorders, e.g., stem cavity, browning and brown core, in `McIntosh' apples.