Abstract

World trade in kiwifruit was based initially on Actinidia chinensis var. deliciosa ‘Hayward’ but has been expanding rapidly in recent years with the introduction of several new yellow-flesh cultivars. The full conversion of flesh color from green to yellow is important for the commercial acceptance of these cultivars. If this conversion is achieved on the vine, it is often associated with earlier fruit softening and, hence, limiting storability. This study determines the effects of early fruit harvest on postharvest degreening in the yellow-flesh kiwifruit ‘Dori’ at different temperatures. Fruit was harvested weekly at three stages of maturity, M1, M2 and M3 (commercial harvest), based on flesh color hue values of 107, 103 and 100°, respectively. Fruit maturity was also characterized on the basis of starch concentration (%), dry matter (%), titratable acidity (%), soluble solids (%) and firmness (N). At each maturity, harvested fruit was degreened at one of three storage temperatures: 0, 5 or 15°C, for 4, 7, 14, 21, 30 or 41 days, then at 20°C for 3, 6 or 9 days. Highest postharvest degreening occurred at 15°C, and varied according to the initial flesh color. After 14 days at 15°C, M1 and M2 achieved hue values of 99-100°, at degreening rates of 0.5 and 0.08° day-1, respectively. In M3 the hue changes were minimal. Kiwifruit from M1 at 15°C softened at the same rate as fruit at 0°C during the first 21 days, with similar concentrations of soluble solids as fruit of M3. Fruit stored at 0°C showed a 40-50% incidence of chilling injury, but injury was half this at 5°C, and absent at 15°C. Degreening early-harvested fruit of ‘Dori’ at 15°C allows maturation to continue postharvest. Further study will determine optimal conditions for associated low-temperature storage and transport.