Influence of maturity stage on the effectiveness of 1-MCP treatment of 'Hayward' kiwifruits during storage

'Hayward' kiwifruits were harvested at a commercial maturity stage with flesh firmness of 59 N (±3.9), soluble solids content (SCC) of 11.5% (±0.6), and titratable acidity (TA) of 1.4% (±0.03). They were then divided in 3 groups and treated at different time during storage with 0.5 ppm of 1-MCP for 24 h. A first group was immediately treated (firm stage), a second group was stored at 0°C for 40 days until 1-MCP treatment when a firmness of 36 N (±1.9) was reached (intermediate stage), while a third group was stored at 0°C for 2 months until treatment when a firmness of 25 N (±1.6) was reached (soft stage). 1-MCP treated samples at firm stage were stored for 100 days at 0°C, while fruits at intermediate and soft maturity stages were stored for 80 days, together with the respective untreated control fruits. Initially upon 1-MCP treatment and during storage, firmness, SSC, TA, respiration rate, vitamin C and total phenolic contents, and antioxidant activity were measured. Untreated firm samples showed a severe firmness loss, which, starting from 23% of the initial value at 20 days of storage, reached 44 and 85% after 60 and 80 days of storage, respectively; treated fruits only lost about 20% of initial firmness after 40 days. At the intermediate stage the effect of 1-MCP treatment resulted evident only after 40 days of storage, when treated samples resulted firmer (about 44%) than the control. Also at the soft stage 1-MCP treatment slowed down softening: firmness decreased of 60 and 54% of initial value for control and treated fruits, respectively during the first days of storage. 1-MCP treatment did not affect chemical composition, while it had a significant effect on respiration rate only for fruits of the firm stage.