An investigation of ripening and handling strategies for early season kiwifruit (Actinidia deliciosa cv Hayward)

Abstract Several strategies for ripening and handling early season kiwifruit ( Actinidia deliciosa (A Chev) Liang et Ferguson cv Hayward) were investigated. Fruit were harvested from the same block of mature vines of kiwifruit in 1985 and 1986, when fruit had reached 5.5 and 6.2% w/v soluble solids concentration (SSC), and treated with ethylene (1 ml litre −1 , 12h, 20°C), either before or after cool storage at 0°C for either 4 or 6 weeks. In addition, the effect of short delays at 20°C and/or ambient temperatures (16–21°C) for up to 5 days prior to ethylene treatment, and the effect of short delays at 20°C for up to 96 h after ethylene treatment prior to cool storage, were assessed. Fruit softening in response to ethylene treatment comprised two phases: a rapid phase lasting 3 to 4 days during which flesh firmness decreased from a harvest firmness of 8–10kgf (kgf × 9.807=N) to approximately 1.5–2kgf, followed by a second, slower phase during which flesh firmness decreased from 2 kgf to an eating firmness of approximately 0.7kgf. Softening was more rapid and uniform in response to ethylene treatment, irrespective of fruit maturity or prior treatment. Delays at ambient temperature and/or 20°C prior to ethylene treatment had no effect on subsequent softening rates. Fruit which had been cool stored at 0°C after ethylene treatment continued to soften but at reduced rates relative to fruit held at 20°C. Increasing delays at 20°C prior to cool storage decreased subsequent storage and shelflife. Softening and ripening rates were similar in fruit of different maturity indices in 1985 but not in 1986. Fruit harvested at 5.5% SSC always had acceptable eating quality if treated with ethylene. The results indicate that several ripening and handling strategies are possible for early season kiwifruit. However, an appropriate maturity index is required to determine how early fruit should be harvested if fruit are to be treated with ethylene for early season marketing.