4种枸橼类柑橘果皮挥发性成分分析

Analysis of volatile substances in peels of four citron varieties

【目的】系统比较4种枸橼类柑橘果皮挥发性成分并筛选差异特征挥发性成分,对利用枸橼类柑橘种质资源及促进柑橘精油产业开发具有重要意义。【方法】采用溶剂萃取结合气相色谱-质谱(GC-MS)联用技术对云柠1号柠檬、红柠檬、香水柠檬和香橼果皮的挥发性成分进行测定。【结果】在云柠1号柠檬、红柠檬、香水柠檬和香橼果皮中共检测出85种挥发性成分,依次检测出72种、57种、58种、58种;从总挥发性成分含量看,云柠1号柠檬>香水柠檬>红柠檬>香橼。通过偏最小二乘法判别分析(PLS-DA),可将4种枸橼类柑橘品种有效区分;以VIP≥1,p<0.05为基准,筛选得到12种差异特征挥发性成分,其中云柠1号柠檬果皮中γ-松油烯、β-桧烯、柠檬醛、β-蒎烯、α-蒎烯、橙花醛的含量显著积累;红柠檬果皮中(Z)-α-佛手柑油烯、α-金合欢烯的含量显著积累,其中α-金合欢烯是红柠檬果皮中所特有的;香水柠檬果皮中D-柠檬烯、香茅醛含量显著积累;香橼果皮中香叶醇、紫苏醛含量显著积累。【结论】不同枸橼类柑橘果皮的挥发性成分种类和含量差异显著,其中D-柠檬烯、γ-松油烯、β-桧烯、香茅醛、柠檬醛、香叶醇、(Z)-α-佛手柑油烯、β-蒎烯、α-蒎烯、α-合金欢烯、紫苏醛、橙花醛可作为这4种枸橼类柑橘果皮的差异特征挥发性成分。云柠1号柠檬和香水柠檬香气成分丰富,可作为优异的柑橘香气资源。

【Objective】Systematic comparative analysis of the volatile components in the peel of four main cultivated citron,screening of the characteristic volatile components in the four citrons and analyz-ing their differences in aroma substances from the perspective of metabolism are of great significance for better utilization of the germplasm resource of citron citrus and promoting the development of citrus essential oil industry.【Methods】The volatile components of YN 1 lemon,Red lemon,Xiangshui lem-on and Citron peels were detected by low temperature ultrasonic solvent extraction combined with GC-MS,and compounds were identified with the Xcalibur software and NIST mass spectrometry database for compound matching,combined with artificial spectrum analysis and comparison with relevant litera-ture.The content of volatile components was determined by the internal standard method,and the data were statistically analyzed by WPS Office 2020 software.SPSS 26.0 software was used to analyze the variance and difference significance of means.Origin 2021 software was used for constructing graphs with the data,and Simca14.1 for multivariate statistical analysis to screen the characteristic volatile components.Partial least square discriminant analysis(PLS-DA)was used to predict the stability and re-liability of the data.【Results】There were significant differences in the types and contents of volatile components in the peel of the four citrons.A total of 85 volatile components were detected in the peels of YN 1 lemon,Red lemon,Xiangshui lemon and Citron,and 72,57,58 and 58 were detected respec-tively,which fell into 11 classes,including monothenes,sesquiterpenes,monoterpene alcohols,sesqui-terpene alcohols,monothene aldehydes,aldehydes,esters,alcohols,etc.Monothene substances accumu-lated significantly,accounting for more than 80%of the total volatile components,among which D-lim-onene was the highest volatile substance in the peels of the four citrons.Among the 85 volatile compo-nents detected,34 were common to the four varieties and they were the typical volatile components of citrons.The peel of YN 1 lemon contained 9 unique volatile components,and the peel of Red lemon contained 7 unique volatile components,while no unique volatile components were detected in the peels of Xiangshui lemon and Citron.YN 1 lemon peel had the highest total volatile component con-tent(24554.42µg·g-1),followed by Xiangshui lemon peel with 22004.48µg·g-1,Red lemon peel with 9677.24µg·g-1,and Citron peel with the lowest content(6671.86µg·g-1).Further,by partial least square discriminant analysis(PLS-DA),the established PLS-DA model could effectively distinguish the vola-tile components of the four citron varieties.The largest contribution to principal component 1(PC1)was D-limonene,followed by citronellal,citral,neral,etc.,and the largest contribution to principal com-ponent 2(PC2)wasβ-pinene,followed byγ-perpinene,α-pinene,β-myrcene,etc.With VIP≥1,p<0.05 as the basis,12 volatile components with different characteristics were screened.Among them,D-limo-nene,γ-terpinene,β-pinene,citral,β-myrcene,α-pinene and neral were significantly accumulated in the peel of YN 1 lemon.(Z)-α-bergamotene andα-farnesene accumulated significantly in the peel of Red lemon,in which(Z)-α-bergamotene was 61.14 times that of YN 1 lemon,5.11 times that of Xiangshui lemon and 281.27 times that of Citron,andα-farnesene was unique to the peel of Red lemon.D-limo-nene and citronellal accumulated significantly in the peel of Xiangshui lemon,especially citronellal,which was 111.77 times that of YN 1 lemon,37.35 times that of Red lemon and 814.44 times that of Cit-ron.Geraniol and perillal accumulated significantly in Citron peel,in which geraniol was 10.57 times that of YN 1 lemon,6.17 times that of Xiangshui lemon,and perillal was 3.66 times that of YN 1 lem-on,and 16.01 times that of Xiangshui lemon.The contents of D-limonene,citral and neral in the peel of YN 1 lemon and Xiangshui lemon were significantly higher than those of Red lemon and Citron.【Con-clusion】There were significant differences in the types and contents of volatile components in different citron citrus peel.Monopetene compounds were the most important volatile components in the peel of the four kinds of citron varieties.The content and types of volatile components in the peel of YN 1 lem-on were the highest,and the content and types of volatile components in the peel of citron were the least.Based on the PLS-DA result,γ-terpinene,β-pinene,α-pinene andβ-myrcene might be the charac-teristic volatile components of YN 1 lemon peel;(Z)-α-bergamotene andα-farnesene were characteristic volatile components of Red lemon peel;citronellal might be used as the characteristic volatile compo-nent of Xiangshui lemon peel,and geraniol and perillal might be used as the distinctive volatile compo-nents of Citron peel.YN 1 lemon and Xiangshui lemon had rich aroma components and might be excel-lent citrus aroma resources.