Postharvest Application of Various Gas Treatments to Improve Passion Fruit Quality

The local Israeli purple passion fruit (Passiflora edulis Sims) line ‘Passion Dream’ (PD) is a hybrid of purple and yellow passion fruits which produces two cycles of fruit a year, in summer and winter. Fresh fruit quality is reduced after ~3 weeks of storage, mainly from shriveling and decay development. Passion fruit is typically collected from the ground after natural abscission; however, these fruit will suffer from damage and are not suitable for export. Here we examined the effect of various postharvest gas treatments aimed at maintaining fruit quality of picked fruit after storage. On the day of harvest, fruit at breaker stage were sealed in 250 L chambers for 24 h at 25 °C and provided with 100 ppm ethylene, 500 ppb 1-methylcyclopropene (1-MCP), 2% ethanol vapors (EtV) or 1% low oxygen atmosphere (LO2). After treatment, fruit was placed in 1-L plastic boxes covered with stretchable shrink film and transferred to storage at 12 °C or 20 °C. In another experiment, we compared the effect of 500 ppb 1-MCP on pink and breaker PD fruits, in order to extend storability. Ethylene levels as well as fruit acidity were initially much higher in winter fruit compared to summer fruit. LO2 enhanced peel color due to anthocyanin accumulation in winter fruit after 12 °C storage, but not in summer fruit. Ethylene treatment increased color development and production of aroma volatiles in breaker fruit, similar to levels in pink fruit, after natural abscission. Aroma volatiles were determined in juice by SPME/GC-MS techniques. In both seasons, 1-MCP, EtV and LO2 delayed ripening by reducing ethylene production, color development and production of aroma volatiles. LO2 and even more so EtV, caused ‘off’ flavors likely due to more ethanol and ethyl esters production. In both summer and winter seasons, fruit treated with 1-MCP at breaker or pink stage and subjected to 12 °C storage and 20 °C shelf life displayed the best appearance, as measured by minimal weight lost, peel shriveling, and decay, enabling 5–6 weeks of postharvest storage life.