Reductive off-odors are a not infrequent outcome of wine production, particularly of bottle aging and are responsible for an important proportion of faulty wines with nasty consequences for the brand image. Such a problem is mostly caused by the development of H2S and Methanethiol (MeSH), although a number of different other volatile sulfur compounds (VSCs) have been also identified. A third relevant molecule, dimethyl sulfide (DMS), is also frequently included within the group of reductive problems.
The reasons why these molecules accumulate during bottle aging, more often in those wines in which these compounds were previously formed in fermentation, are not clearly known. Several hypothesis have been formulated by scientists along the years, most of which have not been ever demonstrated. One of the hypothesis that has received more credibility among winemakers states that the origin of these compounds is the reduction of disulfides or of elemental sulfur.
Only that it is not true! Or at least it is not all the truth! As shown by the findings of Ferreira's team.
Winner of the International OENOPPIA AWARD 2015