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Fingerprint of enological tannins by multiple techniques approach

Laghi, Luca, Parpinello, Giuseppina P., Rio, Daniele Del, Calani, Luca, Mattioli, Alessia U., Versari, Andrea
Food chemistry 2010 v.121 no.3 pp. 783-788
wines, tannins, food analysis, analytical methods, antioxidant activity, spectral analysis, mass spectrometry, food composition, ultraviolet-visible spectroscopy, Fourier transform infrared spectroscopy, nuclear magnetic resonance spectroscopy, size exclusion chromatography, liquid chromatography, electronic nose
In this study, six enological tannins (T1-T6) from different source were analysed by selected analytical techniques, including UV-Vis, FTIR, NMR, SEC, LC-MS/MS and electronic nose. Moreover, the samples were tested for their antioxidant activity. Spectra and chromatograms are considered as a fingerprint with a pattern that is distinctive for a given type of sample. In particular, tannins showed the maximum UV-Vis absorbance (λ max) at 273-280nm, the inflection point (λ min) at 247-264nm, and the ratio λ max/λ min was 1.03, 1.35, 1.67, 1.36, 2.15, 2.02 for tannin T1-T6, respectively. The FTIR analysis of tannins showed the presence of most important absorption bands at 1522, 1453, 1380, 1350, 1328, 1286, 1210, 1148 and 1044cm⁻¹. Besides, SEC and NMR analysis allowed to sort the tannins according to their average DP as follows: T1>T2=T4>T3>T6=T5. Based on this multiple techniques approach three condensed tannins (sample T3, T5 and T6) were clearly identified, together with two mixtures of hydrolysable tannins (sample T1 and T2), whereas one sample (T4) showed a peculiar pattern different from the commercial tannin commonly used in enology.