采收期对青皮核桃抗氧化特性及耐贮性的影响

Effect of Harvest Stage on Antioxidant Property and Storability of Green Walnut Fruits

以8月上、中、下旬采收的中林5号和辽宁4号青皮核桃果实为试材,于0-1℃,相对湿度70%-80%条件下贮藏,测定贮期核桃各抗氧化相关指标及贮藏品质。结果表明：8月下旬采收果实总酚和类黄酮含量在贮藏30 d后呈上升趋势,超氧化物歧化酶（SOD）、过氧化物酶（POD）、过氧化氢酶（CAT）、多酚氧化酶（PPO）均于贮藏30 d后持续增长或出现活性高峰。两品种均为8月中旬采收果实腐烂指数最高,辽宁4号果实腐烂指数总体上高于中林5号;贮藏后各采收期采收果实的碘价均下降,不饱和脂肪酸的相对质量分数均上升,以8月下旬采收果实的碘价下降幅度最小,不饱和脂肪酸的相对质量分数最大。8月下旬采收青皮核桃有助于抗氧化物质的积累及防御酶活性的提高,果实较耐贮。

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.