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Sensors 2016, 16(10), 1654; doi:10.3390/s16101654

Discrimination of Apple Liqueurs (Nalewka) Using a Voltammetric Electronic Tongue, UV-Vis and Raman Spectroscopy

1
Department of Analytical Chemistry, Faculty of Chemistry, Gdansk University of Technology, Narutowicza St. 11/12, 80-233 Gdańsk, Poland
2
Department of Inorganic Chemistry, Engineers School, Universidad de Valladolid, 47011 Valladolid, Spain
3
The NanoBioMedical Centre, Adam Mickiewicz University, Umultowska 85, 61-614 Poznań, Poland
4
Faculty of Physics, Adam Mickiewicz University, Umultowska 85, 61-614 Poznań, Poland
5
Department of Materials Science, Engineers School, University of Valladolid, Valladolid 47011, Spain
*
Author to whom correspondence should be addressed.
Academic Editors: Takeshi Onodera and Kiyoshi Toko
Received: 13 July 2016 / Revised: 9 September 2016 / Accepted: 1 October 2016 / Published: 9 October 2016
(This article belongs to the Special Issue Olfactory and Gustatory Sensors)
View Full-Text   |   Download PDF [3248 KB, uploaded 9 October 2016]   |  

Abstract

The capability of a phthalocyanine-based voltammetric electronic tongue to analyze strong alcoholic beverages has been evaluated and compared with the performance of spectroscopic techniques coupled to chemometrics. Nalewka Polish liqueurs prepared from five apple varieties have been used as a model of strong liqueurs. Principal Component Analysis has demonstrated that the best discrimination between liqueurs prepared from different apple varieties is achieved using the e-tongue and UV-Vis spectroscopy. Raman spectra coupled to chemometrics have not been efficient in discriminating liqueurs. The calculated Euclidean distances and the k-Nearest Neighbors algorithm (kNN) confirmed these results. The main advantage of the e-tongue is that, using PLS-1, good correlations have been found simultaneously with the phenolic content measured by the Folin–Ciocalteu method (R2 of 0.97 in calibration and R2 of 0.93 in validation) and also with the density, a marker of the alcoholic content method (R2 of 0.93 in calibration and R2 of 0.88 in validation). UV-Vis coupled with chemometrics has shown good correlations only with the phenolic content (R2 of 0.99 in calibration and R2 of 0.99 in validation) but correlations with the alcoholic content were low. Raman coupled with chemometrics has shown good correlations only with density (R2 of 0.96 in calibration and R2 of 0.85 in validation). In summary, from the three holistic methods evaluated to analyze strong alcoholic liqueurs, the voltammetric electronic tongue using phthalocyanines as sensing elements is superior to Raman or UV-Vis techniques because it shows an excellent discrimination capability and remarkable correlations with both antioxidant capacity and alcoholic content—the most important parameters to be measured in this type of liqueurs. View Full-Text
Keywords: electronic tongue; voltammetric sensor; UV-Vis; Raman spectroscopy; apple liqueurs; nalewka electronic tongue; voltammetric sensor; UV-Vis; Raman spectroscopy; apple liqueurs; nalewka
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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. (CC BY 4.0).

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MDPI and ACS Style

Śliwińska, M.; Garcia-Hernandez, C.; Kościński, M.; Dymerski, T.; Wardencki, W.; Namieśnik, J.; Śliwińska-Bartkowiak, M.; Jurga, S.; Garcia-Cabezon, C.; Rodriguez-Mendez, M.L. Discrimination of Apple Liqueurs (Nalewka) Using a Voltammetric Electronic Tongue, UV-Vis and Raman Spectroscopy. Sensors 2016, 16, 1654.

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