Effects of N-butanol on chilling injury and active oxygen metabolism of postharvest Hami melon fruits

Abstract:【Objective】The purpose of this work was to investigate the effect of N-butanol on chilling in- jury and active oxygen metabolism of Hami melon (Cucumis melo var. reliculatus) fruits. Hami melon Xizhoumi 25 was used in this experiment【. Methods】The fruits were soaked in the N-butanol treatment solution with a concentration of 1.0% for 30 mins, and the fruits soaked in clear water for the same time were used as control group. After the surfaces were completely air- dried, they were placed in a (3 ±0.5) °C mechanical cold storage for 42 days. Then the Chilling injury incidence, chilling injury index,the activities of catalase (CAT),superoxide dismutase (SOD) and peroxidase (POD), superoxide anion radical (O_ ) production rate and the contents of hydrogen peroxide (H2O2), the activities of glutathione2 reductase (GR), ascorbate peroxidase (APX), the contents of ascorbic acid (ASA) and glutathione (GSH), the dehydroascorbic acid (DHA) content and L-glutathione oxidized (GSSG) content were mea- sured at every seven days【. Results】The results showed that compared with the control group, the N-bu- tanol treatment could reduce the cold injury index of Hami melon fruits in the late storage period (35-42 d). For example, the cold injury index of the control group was as high as 44% when stored for 42 days, while the cold injury index of the group treated with N-butanol was 33%. The symptoms of cold injury were obviously alleviated by N-butanol treatment. The H2O2 content of the fruits treated with N-butanol decreased rapidly 14 days before storage and was higher than that of the control group. However, dur- ing the subsequent storage time(14-42 days)the H₂O₂ content of the two groups of fruits began to rise and reached the maximum value at 28 days of storage, and then it started to decline, and the H2O2 con- tent of N-butanol treatment group was always lower than the that of the control group (Except 35 days) (p < 0.05 ). The O2- · production rate presented a trend of rising, falling, rising and falling. The O2- · pro- duction rate of N-butanol treatment group was always lower than that of the blank control group during the storage , and the inhibitory effect was better (p < 0.05).The superoxide dismutase (SOD) activity of superoxide dismutase was positive during the entire storage period. The N-butanol treatment group was higher than that of the blank control group, and the superoxide dismutase (SOD) activity of the N-buta- nol treatment group was significantly higher than that of the control group after 21, 28, and 42 days of storage. Peroxidase (POD) activity of the N-butanol treatment group was always higher than that of the control group during the middle and late storage period (21-35 days). The catalase (CAT) enzyme activi- ty showed an overall upward trend during the storage, and it was improved bythe N-butanol treatment . In addition, N-butanol treatment also increased the content of ASA-GSH circulating substrates. Statisti- cal analysis revealed that the level of ascorbic acid (ASA) and the ascorbic glutathione (GSH) of the N- butanol treated fruits were significantly higher than that of the control fruits.【Conclusion】The N-buta- nol treatment could induce the production of active oxygen signal molecules in Hami melon fruits, in- crease the activity of active oxygen scavenging enzymes, delay the membrane lipid peroxidation pro- cess, and thereby weaken the occurrence of chilling injury. The research results would provide technical support and theoretical reference for the postharvest storage of Hami melon.