采收期对核桃贮藏期间内种皮褐变的影响

Effect of harvest time on browning of walnut endocarps during storage

【目的】为核桃生产中适宜采收期的确定及贮藏期间内种皮褐变的调控提供理论参考。【方法】以‘香玲’核桃为试验材料,分别于2023年的8月25日(果实发育120 d左右)、9月2日(果实发育128 d左右)、9月10日(果实发育136 d左右)分3次采收,采用增加温度和湿度的方式加速贮藏,定期测定不同采收期核桃内种皮的褐变度、相对电导率、丙二醛(MDA)含量、总酚含量、多酚氧化酶(PPO)活性、超氧化物歧化酶(SOD)活性、过氧化物酶(POD)活性、过氧化氢酶(CAT)活性等褐变相关指标。【结果】随着贮藏时间的延长,各采收期核桃内种皮的褐变度、MDA含量、相对电导率均表现出上升趋势,且9月2日采收的核桃内种皮的褐变度、MDA含量及相对电导率在贮藏后期均显著低于其他采收期的样品;总酚含量、POD活性在贮藏期间均表现为下降趋势,PPO活性在贮藏期间表现为先上升后下降的趋势,与其他采收期相比,在贮藏期间9月2日采收的核桃内种皮总酚含量较高,PPO活性较低;在贮藏期间,核桃内种皮的SOD活性、CAT活性总体呈现上升趋势,其中9月2日采收核桃内种皮的SOD活性和CAT活性显著高于其他采收期的样品。【结论】采收期对贮藏期间核桃内种皮褐变相关生理指标有一定的影响。在贮藏期间,9月2日采收的核桃内种皮能够维持较高的多酚含量及SOD、CAT、POD等抗氧化酶活性,同时能降低PPO活性、相对电导率及MDA含量,减轻褐变程度。

【Objective】To provide a theacademic reference for the determination of the best harvest time and regulation of walnut endocarps browning during storage.【Method】The walnut‘Xiangling’were used as the test material,which fruits were harvested three times on August 25,2023(fruit growth 120 d),September 2,2023(fruit growth 128 d)and September 10,2023(fruit growth 136 d).Then,the fruits were accelerated storage by increasing temperature and humidity.And the browning related indicators of walnut endocarps such as browning degree,relative conductivity,MDA,total phenolic content,PPO,SOD,POD,CAT,etc.were measured regularly in storage period.【Result】With the prolongation of storage time,the browning degree,MDA and relative conductivity of walnut endocarps showed an upward trend,and the browning degree,MDA content and relative conductivity of walnut inner testa harvested on September 2 were significantly lower than those of other harvest periods in the later stage of storage.At the same time,the total phenolic and POD showed a downward trend during storage,and the PPO showed a trend of increasing first and then decreasing during storage.Compared with other harvest periods,the total phenolic of walnut endocarps harvested on September 2 during storage was higher,and the PPO was lower.In addition,the SOD and CAT of walnut endocarps showed an overall upward trend,and the SOD and CAT of walnut endocarps harvested on September 2 were significantly higher than those of other harvest periods.【Conclusion】The harvest time had a certain effects on the physiological indexes related to the browning of walnut endocarps during storage.Among them,the walnut harvested on September 2 could maintain a higher polyphenol content and antioxidant enzyme activities such as SOD,CAT and POD during storage,while reducing PPO,relative conductivity and MDA content,and reducing browning degree.