本项目研究龙眼核精油体外抗氧化性及常温保鲜效果，以有机溶剂正己烷提取龙眼核精油，测定精油对 1,1-二苯基-2-苦肼基自由基（DPPH·）、羟基自由基（·OH）及亚硝酸钠（NaNO2）的清除能力，以龙眼果肉颜色、果皮褐变指数、失重率、可溶性固形物、可滴定酸含量等生理指标变化作为保鲜效果的评判标准。结果表明：龙眼核精油对DPPH·、·OH及NaNO2均有一定清除作用，IC50分别为11.04、4.58、0.12 mg/mL，在试验浓度范围内呈一定量效关系；精油可降低龙眼果皮褐变指数及失重率上升速度；可溶性固形物含量变化起伏小；贮藏前期，可滴定酸含量变化缓慢，后期上升较快；精油处理组与空白对照组间差异不显著（p＞0.05）,龙眼核精油对龙眼果实不具备明显保鲜效果；精油浓度过大会对龙眼果实产生不同程度的药害。

This study investigated the in vitro antioxidant activity and preservative effect at ambient temperature of Longan seed essential oil. Longan seed essential oil was extracted with organic solvent n-hexane for the determination of 1, 1-diphenyl-2-picrylyl (DPPH·) free radical,hydroxyl radicals (·OH) and sodium nitrite (NaNO2) scavenging abilities. The preservative effects were assessed based on the changes in physiological indices including Longan flesh color, peel browning index, weight loss rate, soluble solids content and titratable acidity. The results showed that the Longan seed essential oil exhibited detectable DPPH·, ·OH and NaNO2 scavenging activities, with respective IC50 values as 11.04, 4.58 and 0.12 mg/ mL, and a dose-effect relationship was found within the experimental concentration range. The essential oil can reduce peel browning index and weight loss rate of Longan peel; the change in the soluble solid content was small; the titratable acidity changed slowly in the early stage of storage, but increased rapidly in late stage. There was no significant difference (P ＞ 0.05) between the essential oil-treated group and the control (untreated) group. The Longan seed essential oil did not exert obvious preservative effect on Longan fruit. Excessive essential oil could also cause different degrees of phytotoxicity to Longan fruit.

大学生创新创业训练项目（201714278082）