Lachenmeier Dirk W, Richling Elke, López Mercedes G, Frank Willi, Schreier Peter
Chemisches und Veterinäruntersuchungsamt (CVUA) Karlsruhe, Weissenburger Strasse 3, 76187 Karlsruhe, Germany.
J Agric Food Chem. 2005 Mar 23;53(6):2151-7. doi: 10.1021/jf048637f.
Principal component analysis (PCA) was applied to the chromatographic and spectroscopic data of authentic Mexican tequilas (n = 14) and commercially available samples purchased in Mexico and Germany (n = 24). The scores scatter plot of the first two principal components (PC) of the anions chloride, nitrate, sulfate, acetate, and oxalate accounting for 78% of the variability allowed a classification between tequilas bottled in Mexico and overseas; however, no discrimination between tequila categories was possible. Mexican products had a significantly (p = 0.0014) lower inorganic anion concentration (range = 1.5-5.1 mg/L; mean = 2.5 mg/L) than the products bottled in the importing countries (range = 3.3-62.6 mg/L; mean = 26.3 mg/L). FTIR allowed a rapid screening of density and ethanol as well as the volatile compounds methanol, ethyl acetate, propanol-1, isobutanol, and 2-/3-methyl-1-butanol using partial least-squares regression (precisions = 5.3-29.3%). Using PCA of the volatile compounds, a differentiation between tequila derived from "100% agave" (Agave tequilana Weber var. azul, Agavaceae) and tequila produced with other fermentable sugars ("mixed"tequila) was possible. The first two PCs describe 89% of the total variability of the data. Methanol and isobutanol influenced the variability in PC1, which led to discrimination. The concentrations of methanol and isobutanol were significantly higher (methanol, p = 0.004; isobutanol, p = 0.005) in the 100% agave (methanol, 297.9 +/- 49.5; isobutanol, 251.3 +/- 34.9) than in the mixed tequilas (methanol, 197.8 +/- 118.5; isobutanol, 151.4 +/- 52.8).
主成分分析（PCA）应用于正宗墨西哥龙舌兰酒（n = 14）以及在墨西哥和德国购买的市售样品（n = 24）的色谱和光谱数据。氯离子、硝酸根离子、硫酸根离子、乙酸根离子和草酸根离子的前两个主成分（PC）得分散点图解释了78%的变异性，据此可以区分在墨西哥境内和境外装瓶的龙舌兰酒；然而，无法区分龙舌兰酒的类别。墨西哥产的产品中无机阴离子浓度（范围为1.5 - 5.1 mg/L；平均值为2.5 mg/L）显著低于（p = 0.0014）在进口国装瓶的产品（范围为3.3 - 62.6 mg/L；平均值为26.3 mg/L）。傅里叶变换红外光谱（FTIR）通过偏最小二乘回归（精度为5.3 - 29.3%）能够快速筛选密度、乙醇以及挥发性化合物甲醇、乙酸乙酯、正丙醇、异丁醇和2-/3-甲基-1-丁醇。利用挥发性化合物的主成分分析，可以区分由“100%龙舌兰”（龙舌兰科的蓝色韦伯龙舌兰）制成的龙舌兰酒和用其他可发酵糖制成的龙舌兰酒（“混合”龙舌兰酒）。前两个主成分描述了数据总变异性的89%。甲醇和异丁醇影响了主成分1中的变异性，从而导致了区分。100%龙舌兰酒中的甲醇和异丁醇浓度（甲醇，p = 0.004；异丁醇，p = 0.005）显著高于混合龙舌兰酒（甲醇，297.9±49.5；异丁醇，251.3±34.9）（甲醇，197.8±118.5；异丁醇，151.4±52.8）。
