Effects of exogenous hydrogen peroxide treatment on browning and reactive oxygen metabolism of postharvest litchi

【Objective】To explore the effects of exogenous hydrogen peroxide（H₂O₂）treatment on browning and reactive oxygen metabolism of postharvest litchi, so as to provide a method to keep litchi fresh after harvest and improve the storage quality of litchi.【Method】Litchi was used as material，in contrast to clean water（CK），and soaked with different concentrations（1，5，10 mmol/L）of exogenous H₂O₂ for 3 min，and then placed under 4 ℃，measured once every 3 d， weight loss rate，browning index，malondialdehyde（MDA）content，cell membrane permeability，endogenous H₂O₂ content，superoxide anion（O₂^-）production rate，polyphenol oxidase（PPO）activity，superoxide dismutase（SOD）activity and other physiological indicators were determined.【Result】Different concentrations of exogenous H₂O₂ treatment could produce different storage effects on postharvest litchi. 5 mmol/L exogenous H₂O₂ treatment had the best preservation effect， and it could decrease MDA content，endogenous H₂O₂ content and PPO activity in fruit peel，increase SOD activity，and slow down the production rate of O₂^-. At the end of storage（12 d），SOD activity of postharvest litchi treated with 5 mmol/L exogenous H₂O₂ treatment significantly increased by 31.41%（P<0.05，the same below）compared with CK. Compared with CK，MDA content，PPO activity，O₂^- production rate and endogenous H₂O₂ content were decreased by 44.72%， 38.72%，22.63% and 13.75%，respectively，and weight loss rate，browning index and relative conductivity of postharvest litchi were the lowest. The effect of 1 mmol/L exogenous H₂O₂ treatment was slightly inferior to that of 5 mmol/L exogenous H₂O₂ treatment，while 10 mmol/L exogenous H₂O₂ treatment significantly increased MDA content and endogenous H2O2 content in postharvest litchi，and accelerated the senescence of post-harvest fruits.【Conclusion】5 mmol/L exogenous H₂O₂ treatment can delay the senescence process of litchi by regulating the metabolism of reactive oxygen species，which will provide theoretical support for the application of hydrogen peroxide in the preservation of postharvest litchi.