Multivariate strategies for red wines classification using stilbenes and flavonols content

Abstract

Bioactive polyphenols from grapes and wines, like stilbenes and flavonols (SaF), are often determined to nutritional evaluation, but also for many other purposes. The objective of this study was to quantify SaF in red wines from “Campanha Gaúcha”, a large and young viticultural region from South Brazil. Moreover, through statistical analysis, evaluate the influence of these compounds according to varieties, production process, harvest years and micro-regions of cultivation. A total of 58 samples of red wines were analyzed by high-performance liquid chromatography coupled to diode array detector (HPLC-DAD) for determination of trans-resveratrol (R), quercetin (Q), myricetin (M), kaempferol (K), trans-e-viniferin (V) and their precursor, cinnamic acid (C). During such method validation, the selectivity was confirmed by a high resolution mass spectrometer (QTOF). For statistical analysis, four different data sets were used: wine varieties (34 samples), process influence (58 samples), harvest years (54 samples) and micro-regions (58 samples). The analysis of variance (ANOVA), principal component analysis (PCA) and partial least square discriminant analysis (PLS-DA) were used. The Kennard-Stone algorithm was used to separate the samples into training and test sets. The leave-one-out cross validation method was used to choose the number of latent variables (LVs) in PLS-DA. The limits of detection (LOD) and quantification (LOQ) of (R), (Q), (M), (K), (V) and (C) were, respectively, 0.33 and 1.01, 0.30 and 0.90, 0.23 and 0.69, 0.27 and 0.81, 0.23 and 0.70, 0.02 and 0.05 µg mL-1. The concentration of (C) was below the LOQ in all samples, since it is consumed to synthesize the studied SaF. According to ANOVA, the SaF concentrations changed significantly due to the influence of the studied parameters. However, no patterns were observed in the scores of the first three principal components (PCs) of the PCA for harvest year and micro-regions data set. A tendency of separation was observed in the PCA scores for different varieties and processing data set. Through PLS-DA, it was possible to satisfactorily predict the wine variety and the processing through the concentration of SaF in terms of sensitivity and specificity. These figures of merit were between 67-100% for both data sets. These results indicate that the concentration of secondary metabolites trans-resveratrol, quercetin, myricetin, kaempferol and trans-e-viniferin, determined by HPLC-DAD, have the potential to measure the variation of red wines between micro-regions from “Campanha Gaúcha”. Consequently, it may be part of an efficient strategy to elaborate different styles of wines adapted to a whole region.