Changes in the softening and composition of kiwifruit(Actinidia deliciosa) Affected by Maturity at Harvest and Postharvest Treatments

Kiwifruit ( Actinidia deliciosa (A Chev) Liang et Ferguson cv Hayward) were harvested at a range of maturities, from 4.4‐8.9% w/v soluble solids, and ripened, with or without ethylene, after harvest or after storage for up to 12 weeks at 0 or 4°C. During maturation, the internal ethylene concentration of the fruit increased, and the lag before the onset of rapid softening decreased. Fruit harvested late in the season and ripened at 20°C softened as rapidly as similar fruit treated with ethylene. This occurred both immediately after harvest and after 6 weeks in storage at 0°C. In more mature fruit, and fruit stored at 0°C, the difference between core and flesh firmness was greater than in immature fruit or that ripened at 20°C immediately after harvest. After 6 weeks in storage, softening of the flesh was almost complete and core firmness had the greatest influence on fruit firmness. Soluble solids concentration increased as fruit softened, but during the first phase of softening soluble solids concentration was higher if the fruit were at low temperatures (or at 20°C without ethylene treatment) than if they were ethylene treated and held at 20°C. Sucrose increased and starch decreased during softening regardless of treatment. Citrate decreased during softening at 20°C and 12 weeks in storage at 0°C. Fructose/glucose ratios were lower in ethylene‐treated fruit than in untreated fruit. Malate did not change much on ripening after harvest but increased in response to low temperature, especially during storage at 4°C. These differences were also found in the eating‐ripe fruit.