Impact of aging on dimethyl sulfide (DMS) in Corvina and Corvinone wines

Abstract

Dimethyl sulfide (DMS) is a low molecular weight sulfur compound produced in wine during aging by the chemical degradation of S-Methyl-L-methionine (SMM). Investigating the aromatic profile of Amarone commercial wines from different wineries, it was found that DMS presented a high variation in concentration across wine samples ranging from 2.88 to 64.34 μg/L, which potentially can affect the perceived aroma. Therefore, in order to investigate this variation, the influence of grape variety, withering, precursor, and vintage on DMS formation was studied. To achieve this a set of experimental wines, vintage 2017, 2018 and 2019 made with Corvina and Corvinone (fresh and withered) grapes from five different vineyards was submitted to accelerated aging. Samples in duplicate were kept at 45 °C for 24, 48, and 96 days, and then analyzed by HS-SPME GC-MS to determine their DMS content. Results showed minor increases in all samples at 24 and 48 days, whereas a considerable accumulation of DMS occurred at 96 days with concentrations approaching values around 120 μg/L. Additionally, it was observed that wines made from withered grapes presented higher concentrations respect to those made with fresh grapes, while the grape variety did not show a significant difference. The precursor influence in the wines was explored as well through the correlation between DMS concentration and primary amino acid nitrogen (PAN) content in wines (before aging). PAN content was measured at 340 nm in an automatic analyzer. In wines from vintage 2017, a good correlation (R2=0.7742) was found between the DMS (concentration of DMS at 96 days minus initial concentration) and PAN. While for wines from vintage 2018 and 2019, the correlation was 0.5581 and 0.4043, respectively. Finally, in order to further elucidate additional factors related to the variability in the ability of wines to generate DMS during aging, the influence of pH was also investigated. For this, two sets of wine, one spiked with SMM, were submitted to accelerated aging (one month, 45 °C), in which pH was adjusted to 3 and 4. Results showed an increase in DMS of 10% in the samples with pH 4, which could be explained by the stability of SMM in acid conditions, therefore, at a higher pH, the precursor could be more prone to release DMS.  Concluding, this study points out PAN as a potential tool to predict the production of DMS during aging. As well as providing some indications of the influence of withering in DMS production.