Abstract:

Green walnut fruits from two cultivars, Zhonglin 5 and Liaoning 4 were harvested in early, middle and late
August, and stored at 0–1 ℃ and a relative humidity (RH) 70%–80%. Physiological indices of green husk and quality
traits of kernel during the storage were evaluated. The results showed that total phenolic and flavonoid contents present
an increasing trend after the 30th day of storage in fruits harvested in late August, and the activities of SOD, POD,
CAT and PPO increased continuously or reached a peak after the 30th day of storage. For both cultivars, middle August
provided the highest fruit decay index among three harvest stages, and Liaoning 4 showed an overall higher fruit decay
index than Zhonglin 5. After storage, green walnut fruits harvested at each stage presented a decrease in iodine values
and an increase in the relative contents of unsaturated fatty acids. Moreover, the smallest reduction in iodine values
and the highest relative contents of unsaturated fatty acids were observed for fruits harvested in late August. This
harvest stage was beneficial for the accumulation of antioxidant substances and the induction of defensive enzyme
activities and resulted in enhanced disease resistance in green walnut fruits.

Key words: green walnut fruit, variety, harvest stage, antioxidant property, storability