title: Multivariate analysis of FTIR and ion chromatographic data for the quality control of tequila.
abstract: 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).
authors.affiliation: Chemisches und Veterinäruntersuchungsamt (CVUA) Karlsruhe, Weissenburger Strasse 3, 76187 Karlsruhe, Germany. Lachenmeier@web.de
authors.forename: Dirk W
authors.initials: DW
authors.lastname: Lachenmeier
authors.forename: Elke
authors.initials: E
authors.lastname: Richling
authors.forename: Mercedes G
authors.initials: MG
authors.lastname: López
authors.forename: Willi
authors.initials: W
authors.lastname: Frank
authors.forename: Peter
authors.initials: P
authors.lastname: Schreier
mesh_terms: D027882:Agave / Q000737:chemistry*; D000434:Alcoholic Beverages / Q000032:analysis*; D000704:Analysis of Variance; D000838:Anions / Q000032:analysis; D000440:Butanols / Q000032:analysis; D002845:Chromatography / Q000379:methods*; D005506:Food Contamination / Q000032:analysis; D000432:Methanol / Q000032:analysis; D011786:Quality Control; D017550:Spectroscopy, Fourier Transform Infrared
chemical_list: D000838:Anions; D000440:Butanols; C040507:isobutyl alcohol; D000432:Methanol