Oak wood barrel tannin potential builds white wines oxidative stability and contributes to wine metabolomics fingerprint

Abstract

Considerable advances have been made in the chemical characterization of wine metabolites through its holistic study using both targeted and untargeted metabolomics approach. The metabolite pool is subject to an intense molecular dialogue which reinforces the wine complexity even after bottling. The wine oxidative stability might be understood as the intrinsic matrix capacity to prevent aroma deterioration due to oxidative processes. Barrel aging in oak wood is a key element of the elaboration of premium white wines. We have shown that the oak wood tannin potential can influence the wine character and its oxidative status. Here, we report the cross-analysis of the evolution of the antioxidant capacity and related metabolomic fingerprint for white wines made from three distinct varieties (Chardonnay, Semillon, Sauvignon) in barrels with distinct tannin potential. 

The sample set was made of 10 bottles of 2016 Chardonnay where 5 were raised in low tannin potential (LTP) barrels and 5 in medium tannin potential (MTP) barrels; 6 bottles of 2016 Sauvignon (3 LTP and 3 MTP). Fourteen bottles of blends of Sauvignon and Semillon of two vintages (6 bottles of 2016 and 8 of 2017) were also considered to compare new barrel aging to the aging in already used barrel. Wines were assayed for their ability to scavenge DPPH radical, and they were analyzed through untargeted UPLC-Q-Tof-MS and targeted GC-TQ-MS analyses. The untargeted metabolomics approach revealed molecular fingerprints (elemental composition determination) resulting from complex interactions between the wine matrix and the tannin potential. In brief, wines aged in MTP barrel presented a higher density of CHON features in the lower mass range (100-350 Da), while wines aged in LTP barrel rather presented higher density in higher mass range (350-650 Da). This indicated that wines aged in MTP were richer in compounds like mono and di-amino acid peptides that mostly correlated with wine antioxidant capacity (evaluated as EC20) when LTP rather contained oligopeptides. The analysis of the wine volatile profile revealed differences between varieties as well as barrel tannin potential distinction. Thus, LTP presented higher contents in γ-octalactone, γ-nonalactone, furaneol, β-damascenone, furfural, gaiacol, E-whiskylactone and Z-whiskylactone. The present study provided evidence that new MTP oak wood barrels are the most suitable to extend the white wine oxidative stability and to maintain a varietal signature.