H2O2对采后龙眼果实果皮褐变的促进及其与活性氧代谢的关系

Effects of H2O2 (hydrogen peroxide), an exogenous reactive oxygen, on browning and active oxygen metabolism in pericarp of harvested longan fruits were investigated in this paper. The harvested longan fruits were dipped in 6% H2O2 for 20 min, while, the control fruits were dipped in distilled water. The fruits were dried prior to packaging and stored at (15±1)℃. During fruit storage, pericarp browning index, contents of malondialdehyde (MDA), relative leakage rate of cell membrane, production rate, activities of active oxygen scavenging enzymes such as superoxide dismutase (SOD), catalase (CAT) and ascorbate peroxidase (APX), contents of endogenous antioxidant substances such as ascorbic acid (AsA) , glutathione (GSH) and carotenoid were determined. The result showed that，as compared the control fruits, there was a higher browning index in pericarp of H2O2-treated longan fruits. The longan fruits treated with H2O2 resulted in increased rate of production and kept higher rate of O2-. production during the whole storage, reduced the activities of SOD, CAT and APX, decreased amounts of AsA, GSH and carotenoid, and increased MDA content and relative leakage rate of cell membrane. From the results it can be concluded that H2O2-induced browning of longan pericarp may be due to the increased the production of active oxygen, the decreased the capacity of scavenging active oxygen and the accumulation of active oxygen caused by H2O2 treatment, which may destroy cell membrane system, allowing phenolase to react with phenolic substrates and oxidation phenolics to form brown polymers.