RED WINE AGING THROUGH ¹H-NMR METABOLOMICS

Abstract

Premium red wines are often aged in oak barrel. This widespread winemaking process is used, among others, to provide roundness and complexity to the wine. The study of wine evolution during barrel aging is crucial to better ensure control of wine quality.

¹H-NMR has already been proved to be an efficient tool to monitor winemaking process [1]. Indeed, it is a non-destructive technique, it requires a small amount of sample and a short time of analysis, yet it provides clues about several chemical families. The aim of the present study is to investigate the evolution of wine during aging in oak barrels with NMR-based metabolomics.

Red wines, produced in an estate of Bordeaux region, were kept in oak barrels from three different manufacturers. They were firstly sampled after one month of aging. They were then resampled after twelve months of storage in oak barrels within the estate cellar. The evolution of wine constituents during aging was measured by ¹H-NMR-based metabolomics. NMR spectra were submitted to targeted and untargeted approaches.

Data were then statistically processed through multivariate statistical analysis such as principal component analysis (PCA), and orthogonal projections to latent structures discriminant analysis (OPLS-DA). It was used to better watch the distribution of metabolic variance, and to sharpen the separation between observations groups. The results of supervised models were validated using cross permutation tests and ANOVA. Statistical significances were then assessed for the potential discriminant compounds thanks to analysis of variance (ANOVA) or t-test. Based on this analysis, wine maturation effect was monitored, and discriminant metabolites were identified.

Regarding aging effect, wines analyzed after one month of aging exhibit higher contents of amino acids, catechin and epicatechin, acetoin and choline. On another side, wines analyzed after twelve months of aging present higher contents of acetic acid, ethyl lactate, arabinose, and glucose.

As it concerns barrel origins, samples showed higher heterogeneity after one month than after twelve months. However, significant differences were observed between wines depending on the barrel manufacturers.