Effects Of Chemical Treatment On Antioxidative Properties Of Fresh-cut Broccoli Florets

Fresh-cut broccoli is easy to deteriorate and has short shelf-life time. In order to study the effects of exogenous 6-benzyladenine?6-BA?, gibberellin?GA?, salicylic acid?SA?, hydrogen peroxide?H₂O₂?, calcium chloride?Ca Cl₂?, ethanol and 1-methylcyclopropene?1-MCP? on the preservation effects and antioxidant properties of fresh-cut broccoli florets, fresh-cut broccoli florets were soaked or fumigated with different concentrations of seven kinds of chemicals. Sensory qualities of fresh-cut broccoli florets in 20°C storage for 4 days were evaluated. According to results of the sensory evaluation, appropriate treatment concentrations were chosen. Then fresh-cut broccoli florets were treated with distilled water and corresponding chemical treatments. Antioxidative enzyme activities, antioxidative substances contents, reactive oxygen species level and senescence physiological indicators of fresh-cut broccoli florets were investigated during cold storage of 10 days at 8°C and room temperature storage of 4 days at 20°C. Each indictor was compared between 6-BA and GA, SA and H₂O₂, Ca Cl₂ and ethanol. The antioxidative mechanisms of delaying fresh-cut broccoli florets senescence of different chemical treatments were discussed.The results indicated that exogenous 6-BA 50 mg/L, GA 120 mg/L, SA 0.5 mmol/L, H₂O₂ 0.15 mmol/L, Ca Cl₂ 0.05 mol/L, ethanol 6 m L/kg and 1-MCP 2.5 ?L/L treatments could effectively delay senescence and maintain the sensory qualities of fresh-cut broccoli florets. Compared with distilled water control, fresh-cut broccoli florets treated with chemical treatments had higher activities of superoxide dismutase?SOD?, catalase?CAT? and ascorbate peroxidase?APX? and lower activity of peroxidase?POD?. The contents of ascorbic acid and carotenoid were higher. The generating rate of superoxide anion?O2??? was smaller, and the content of endogenous H₂O₂ was smaller. The contents of chlorophyll and protein were higher and the content of malondialdehyde?MDA? was less. But exogenous SA treatment showed low CAT activity and higher level H₂O₂ during the storage. The impact of each indicator of antioxidant properties and the preservation effects of 6-BA 50mg/L were better than 50 GA 120 mg/L, SA 0.5 mmol/L were better than H₂O₂ 0.15 mmol/L, ethanol 6 m L/kg were better than Ca Cl₂ 0.05 mol/L. In both cold temperature and room temperature the change trend of antioxidant properties of various exogenous chemical treatments was similar.The above results showed that appropriate concentrations of exogenous 6-BA, GA, SA, H₂O₂, Ca Cl₂, ethanol and 1-MCP treatments could delay senescence and maintain sensory qualities of fresh-cut broccoli. The mechanism was associated with improving SOD?CAT?APX and POD activities and delaying ascorbic acid and carotenoid contents degradation, inhibiting of O2·—and H₂O₂ and MDA levels and alleviating the damage of reactive oxygen species to chlorophyll and protein. The antioxidant mechanism was influenced slightly by the storage temperature.