Determination of total polyphenol index in wines employing a voltammetric electronic tongue

Abstract

This work reports the application of a voltammetric electronic tongue system (ET) made from an array of modified graphite-epoxy composites plus a gold microelectrode in the qualitative and quantitative analysis of polyphenols found in wine. Wine samples were analyzed using cyclic voltammetry without any sample pretreatment. The obtained responses were preprocessed employing discrete wavelet transform (DWT) in order to compress and extract significant features from the voltammetric signals, and the obtained approximation coefficients fed a multivariate calibration method (artificial neural network-ANN-or partial least squares-PLS-) which accomplished the quantification of total polyphenol content. External test subset samples results were compared with the ones obtained with the Folin-Ciocalteu (FC) method and UV absorbance polyphenol index (I(280)) as reference values, with highly significant correlation coefficients of 0.979 and 0.963 in the range from 50 to 2400 mg L(-1) gallic acid equivalents, respectively. In a separate experiment, qualitative discrimination of different polyphenols found in wine was also assessed by principal component analysis (PCA).

Voltammetric and spectrometric determination of antioxidant capacity of selected wines

“…The first observation that can be taken from Tables 1 and 2 is that red wines present higher antioxidant capacity than white ones, which is in agreement with the expected results [16,21,22,23]. For instance, the average EC 50 for red and white dry wines were 20.1 µL (n = 27) and 98.4 µL (n = 6), respectively.…”

“…Moreover, small correlations have been A c c e p t e d M a n u s c r i p t 16 found even between similar methodologies [4,13,18]. Such fact reinforces the use of electroanalytical approach, which is less expensive and simple, thus it showed to be at least two times faster.…”

“…Nevertheless, to the best of our knowledge no study involving a wide and diverse variety of wines has been conducted. Thus, other researchers have shown that red wines has far greater antioxidant capacity than white wines, but the ageing of the grape variety may have no expressive influence [6,11,14,16,17,24].…”

“…The total polyphenol index of wines was also determined by using an electronic tongue and multivariate calibration, but the relationship between polyphenol content and antioxidant capacity was not discussed in this approach [16]. Furthermore, most papers have A c c e p t e d M a n u s c r i p t 5 focused on a low number of samples, mostly red and white wines, from a single geographical area [6,11,14,16,17]. Thus, the aim of this work was to evaluate the antioxidant activity of a range of wines from geographically distinct locations, different quality levels and varied production techniques.…”

A nondestructive method for fish freshness determination with electronic tongue combined with linear and non-linear multivariate algorithms

“…The E-tongue technologies coupled with multivariate algorithms have proved to be a powerful analytical tool widely applied in food quality analysis of such products as wine (Cetó et al 2012;Kirsanov et al 2012), tea (Ghosh et al 2012), milk (Wei et al 2013), oil (Men et al 2013), meat (Campos et al 2010), cocoa (Teye et al 2014) etc., and have been found to be simple, rapid, convenient, reliable, and accurate methods.…”