基于GC×GC/TOF MS对不同等级食用酒精挥发性成分的判别分析

Discriminant Analysis of Volatile Components of Different Quality Grades of Edible Alcohol Based on GC×GC/TOF MS

由于食用酒精挥发性成分含量极低,而这些含量极低的挥发性成分直接影响着食用酒精的口感及等级划分。因此,研究以优级和特级食用酒精为对象,采用顶空固相微萃取结合全二维气相色谱/飞行时间质谱联用技术对2种等级食用酒精进行挥发性成分的定性和定量分析。再以不同等级食用酒精中挥发性成分为变量,采用主成分分析(PCA)、偏最小二乘-判别分析(PLS-DA)等多元统计学方法建立了食用酒精等级判别模型,找出了2种等级食用酒精的主要差异化合物。结果表明:在优级和特级食用酒精中共鉴定出60种挥发性化合物。建立的判别模型能有效地将优级和特级食用酒精区分开,PCA辨别模型的前2个主成分贡献率为51.3%,说明模型具有较好的食用酒精等级区分能力;PLS-DA辨别模型的因变量拟合指数为0.966,模型预测精度为0.934,说明模型具有较好的稳定性和预测能力。基于变量投影重要性分析,判别出23种可区分优级、特级食用酒精的主要差异化合物。其中,特级食用酒精中的癸酸乙酯、正辛烷、顺-β-甲基苯乙烯含量显著高于优级食用酒精;优级食用酒精中乙缩醛、丁酸乙酯、2,6-二叔丁基对甲苯酚、戊酸乙酯、苯乙烯、庚酸乙酯、乙酸乙酯、己酸乙酯、乙酸、苯甲酸乙酯、丙醇、1-甲基萘、壬醛、正己烷、苯甲醛、1,2,3,4-四氢萘、正丙基苯、(-)-柠檬烯、γ-丁内酯、己醛含量显著高于特级食用酒精。2种等级食用酒精挥发性成分相对含量差异最大的为乙缩醛、丁酸乙酯、2,6-二叔丁基对甲苯酚和戊酸乙酯4种化合物。希望研究结果可为不同等级食用酒精的客观辨别提供数据参考和理论支撑。

The content of volatile components in edible alcohol is extremely low.However,these low volatile components directly affect the taste and grading of edible alcohol.Therefore,the superior and super grade edible alcohol were used as the research objects.The qualitative and quantitative analysis of the volatile components in the two grades of edible alcohol were performed by headspace solid-phase microextraction coupled with comprehensive two-dimensional gas chromatography/time of flight mass spectrometry(GC×GC/TOF MS).The volatile compounds identified in different grades of edible alcohol were used as variables,and multivariate statistical methods such as principal component analysis(PCA)and partial least squares-discriminant analysis(PLS-DA)were used to establish a discriminant model for edible alcohol grading,and identified the main differential compounds between the two grades of edible alcohol.The results showed that a total of 60 volatile compounds were identified in edible alcohol of the superior and super grade.The discriminative model could effectively distinguish the edible alcohol of the super grade from superior grade.The contribution rate of the first two principal components of the PCA discrimination model was 51.3%,indicating that the model had good ability to differentiate edible alcohol grades.The fit index of the dependent variable of the PLS-DA discrimination model was 0.966,and the prediction accuracy of the model was 0.934,indicating that the model had good stability and prediction ability.Based on the analysis of the projection importance of the variables,23 marker compounds were discriminated to distinguish between superior and super grade edible alcohol.Among them,the contents of ethyl decanoate,n-octane and cis-β-methylstyrene were significantly higher in super grade edible alcohol than those in superior grade edible alcohol.The contents of acetal,ethyl butyrate,2,6-di-tert-butyl-p-methylphenol,ethyl valerate,styrene,ethyl heptanoate,ethyl acetate,ethyl hexanoate,acetic acid,ethyl benzoate,propanol,1-methylnaphthalene,nonanal,n-hexane,benzaldehyde,1,2,3,4-tetrahydronaphthalene,n-propylbenzene,(-)-limonene,γ-butyrolactone and hexanal were significantly higher in superior grade edible alcohol than those in super grade edible alcohol.The largest differences in the relative content of volatile components between the two grades of edible alcohol were acetal,ethyl butyrate,2,6-di-tert-butyl-p-cresol and ethyl pentanoate.The results of the study were hoped to provide data reference and theoretical support for the objective discrimination of different grades of edible alcohol.