Effect of harvest time on browning of walnut endocarps during storage
[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.
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