Study of chemical and sensory properties of Loureiro monovarietal wines from portuguese Vinho Verde Region: a chemometric approach

Monovarietal white wines produced in the Demarcated Vinho Verde Region are distinguished by their characteristic flavor and color, revealing the variety that gave rise to them. Thus, the aim of this study was to characterize the chemical composition, namely phenolic composition of Loureiro monovarietal wines, from different Vinho Verde sub-regions (Sousa, Lima, Cávado and Melgaço) of 2014 vintage. It was also performed a Categorical Principal Components Analysis (CATPCA) correlating these data with the sensory profile of the different wines analyzed. A non-parametric MANOVA was used to statistically analyze the results, for there was no assumptions of normality and homogeneity of variance-covariance matrices. To identify significant differences between samples, it was performed the Kruskal-Wallis test, followed by the multiple comparison of means of orders (SPSS software Statistics, version 22.0) considering a probability of error type I () of 0.05. In the monovarietal Loureiro wines, significant differences in relation to the physico-chemical parameters: dry extract, reducing sugars and glucose/fructose ratio were found. Regarding the dry extract, the QLI, QDM and QCL wines present a significantly higher level (25.5 to 23.9 g/L), also being these wines those with a significant content of reducing sugars, 8.71 to 6.51 g/L. Concerning the chemical parameters related to color and phenolic composition, the color ranged from 0.070 - 0.084 u.a., total phenolics from 277 - 371 mg gallic acid/L, flavonoids between 143-201 mg gallic acid/L and non-flavonoids between 132-169 mg gallic acid/L. There were only significant differences in the content of phenolic acids (gallic acid and coutaric acid isomer) and catechin. The sensory profile of the seven Loureiro wines is quite similar, however, one wine –QPLL- shows a lower score in the attributes related to the nasal perception (aroma), ortho-nasal perception (flavor) and mouthfeel. When we correlate these data with the chemical data, the CATPCA clearly shows the detachment of QPLL wine from the other wines. Being this the only wine of Lima Vinho Verde Sub-Region, these differences probably occur due to the different terroir.

This work was partially funded by Chemical Research Centre of Vila Real (CQ-VR). University of Trás-os-Montes and Alto Douro. School of Life Sciences and Environment and by Portuguese Funds through FCT — Fundação para a Ciência e a Tecnologia, within the Project UID/MAT/00013/2013.