2019 ASHS Annual Conference

The efficacy of different formulations of a new ethylene antagonist, 1H-cyclopropa[b]naphthalene (NC), on the postharvest physiology and quality of Japanese plum was investigated. Two independent experiments were conducted with Japanese plum cultivars namely ‘Tegan Blue’ and ‘Angeleno’. In both experiments, plum fruit were harvested at commercial maturity and the fruit free from diseases or injuries were subjected to five different formulations i.e., NC fumigation (1 µM) for 18 h and spray treatments on the fruit surface with NC aqueous solution (2 µM) containing 5 % ethanol, NC aqueous solution (2 µM) containing 0.02 % Tween-20, NC aqueous solution (2µM) containing 5 % β-cyclodextrin or NC aqueous solution (2 µM) only, at the room temperature (20±1 °C). The untreated plum fruit were considered as control. In the first experiment, the treated and untreated ‘Tegan Blue’ plums were stored at ambient temperature (20 ±1 °C, 85±5 % RH) for 10 days and at 0 ± 1 °C (90±5 % RH) for 40-days. In the second experiment, the treated and untreated ‘Angeleno’ plum fruit were stored at 0 ±1°C (90±5% RH) for 25 and 40 days. In both experiments, the ethylene production (nmol kg^-1 hr ^-1), respiration rate (mmol kg^-1 hr ^-1), weight loss (%), fruit firmness (N), soluble solid content (SSC) (%), titratable acidity (TA) (%), SSC:TA , individual sugars and organic acids (g kg^-1), total phenols (g kg^-1 GAE), vitamin C (mg kg^-1), anthocyanin (g kg^-1) and total antioxidant activity (µM kg^-1 Trolox) were determined at the end of each respective storage periods. The ‘Tegan Blue’ and ‘Angeleno’ plum fruit treated with NC regardless of type of formulations exhibited significantly suppressed and delayed climacteric peak of ethylene production, reduced percent weight loss and higher fruit firmness. The levels of SSC, SSC:TA and individual sugars were lower whilst TA and individual organic acids concentrations were higher in NC-treated plums as compared to the control fruit. However, the NC fumigation treatment was significantly more effective in maintaining the studied fruit quality parameters as compared to other NC formulations. The levels of total phenols, vitamin C, anthocyanin and total antioxidant activity were not generally affected with NC treatments. Overall, NC delayed the ripening and maintained the postharvest fruit quality of ‘Tegan Blue’ and ‘Angeleno’ plums. The presence of co-solvent or surfactant in preparation of spray solutions enhance the effectiveness of NC application in antagonising action of ethylene.