Original research article by

Inès Le Mao, Grégory Da Costa, Guillaume Leleu, Tristan Richard

 

Wine maturation in oak barrels is a well-known winemaking practice that, among other things, brings roundness and complexity to wine. Studying wine evolution during barrel maturation is crucial to ensure wine quality. Red wines produced in a wine growing estate of the Bordeaux region were monitored after one and twelve months of maturation in oak barrels in the estate’s cellar. Wines were kept in oak casks from three different manufacturers. The evolution of the wine constituents during maturation was monitored by 1H NMR-based metabolomics combined with multivariate statistical analysis. NMR spectra were submitted to targeted and untargeted approaches. The wine maturation effects were thereby monitored and the discriminant metabolites identified. The wines analysed after one month of maturation exhibit higher contents of amino acids, catechin and epicatechin, acetoin and choline than the wines analysed twelve months after maturation; for their part, the latter wines showed higher contents of acetic acid, ethyl lactate, arabinose and glucose. In addition, significant differences were observed between the wines depending on the barrel manufacturers.

Introduction

  Maturation of wine occurs between the end of the maceration and the bottling stage. Wine can be stored in different containers, including stainless-steel tanks, concrete tanks or oak barrels. Oak barrel maturing is very popular nowadays, because it positively influences the quality and aromas of the wines (Garde-Cerdán & Ancín-Azpilicueta, 2006). Many Bordeaux wines, especially the famous ones, are matured in oak barrels. The use of a barrel is not enough to produce a wine of high quality. It is also necessary to carry out this oenological method in a sustained way and with expertise. Wine ageing in an oak barrel promotes a balance between oxygen and the various constituents of wine, such as tannins, colours, aromas, proteins and enzymes. During this stage, wine is subject to many chemical changes due to reactions between the wine constituents, the micro-oxygenation through the staves and the compounds extracted from the oak barrel (Fernández de Simón et al., 2014; Maioli et al., 2022).

Recently, 1H NMR-based metabolomics has emerged as a meaningful tool to ensure the traceability of alcoholic beverages, such as spirits (Teipel et al., 2020) and wines (Le Mao et al., 2023; Solovyev et al., 2021; Valls Fonayet et al., 2021). Based on quantitative analysis (targeted approach) or fingerprinting (untargeted approach), NMR metabolomics can be used to control geographical origin, real composition (including grape variety, for example) and vintage. More recently, 1H NMR-based metabolomics has been used successfully to monitor wine quality during the winemaking process (Le Mao et al., 2021; López-Rituerto et al., 2022).

Red wine maturation in oak barrels induces numerous chemical transformations as a result of different mechanisms, including oxidative reactions and compounds released from oak (Alcaide-Hidalgo et al., 2007; Ma et al., 2022). In turn, this maturation process induces significant sensory changes in the final wine. Recently, Cassino et al. have demonstrated the interest of applying 1H NMR when investigating wine evolution during bottle ageing (Cassino et al., 2019). The aim of the present study was to investigate the evolution of wine during maturation in oak barrels via NMR-based metabolomics. Monitoring wine compound evolution during maturation could be useful for controlling overall wine quality. Red wine was conserved in new oak barrels provided by three different manufacturers, and analysed after one and twelve months conservation in the controlled environment of a cellar. The wine constituents were monitored via 1H NMR spectrometry combined with multivariate statistical analysis.