UNEXPECTED PRODUCTION OF DMS POTENTIAL DURING ALCOOLIC FERMENTATION FROM MODEL CHAMPAGNE-LIKE MUSTS

Abstract

The overall quality of aged wines is in part due to the development of complex aromas over a long period (1.) The apparition of this aromatic complexity depends on multiple chemical reactions that include the liberation of odorous compounds from non-odorous precursors. One example of this phenomenon is found in dimethyl sulphide (DMS) which, with its characteristic odor truffle, is a known contributor to the bouquet of premium aged wine bouquet (1). DMS supposedly accumulates during the ten first years of ageing thanks to the hydrolysis of its precursor dimethylsulfoniopropionate (DMSp.) DMSp is a possible secondary by-product from the degradation of S-methylmethionine (SMM), an amino acid identified in grapes (2), which can be metabolized by yeast during alcoholic fermentation. As a consequence, the totality of DMSp is not released into a young wine (3). Previous studies show that DMS and DMSp are effective as quality indicators for Champagne wines.

However, in beer, dimethyl sulphide (DMS) is either the result of the reduction of dimethylsulfoxide (DMSO) or the hydrolysis of DMSp, and is also linked with the fermentative process (4). Our current question: is the DMS present in wines liberated exclusively from DMSp of vegetal origin – i.e., produced by the vines – or do yeast likewise contribute DMSp during fermentation?

That question is particularly important in the case of Champagne wines because of the double fermentation required for its production. As part of an ongoing study of these Champagne base wines, lies production using Saccharomyces cerevisiae in both grape must and model solutions were standardized at a laboratory level. Modalities omitting DMSp and DMS in the original solution allowed us to monitor the appearance of DMSp during and post-fermentation. While the yeast in these modalities did not initially produce DMS, concentrations of DMSp rose from the onset of fermentation. Further analysis showed this onset coincided with a dramatic drop in methionine concentrations in the fermenting must. While the precise correlation is still being determined, these initial results showed DMSp can originate in both the vineyard and from yeast activity during fermentation, and implies that it may be possible to improve aging quality production using oenological techniques.