Dimethyl Sulfide (DMS) is a chemical compound with a potent aroma that can be found in many foods and beverages. In fact, it can be found in wine and beer, but also in cooked meat, cheese, tomatoes, citrus, melons, truffles, cereals, and vegetables.
But, as an aromatic component is it a good attribute or a defect?
When perceived in high concentration DMS has an odor which can be very unpleasant leading it to often be considered giving an "off" flavor with notes of cooked corn, tomato and asparagus. However, interestingly, in lower concentrations it can often enhance the complexity of the bouquet of food and wine. Therefore, in wines, DMS can be perceived either positively or negatively, depending on its concentration and the type of wine.
DMS is always generated during fermentation, but due to its high volatility the left-over concentration in young wines is often too low to be perceived. Conversely, while a red wine ages in the bottle, the DMS concentration grows again reaching a peak after 10-15 years. Therefore, it can be perceived in certain aged, red wines.
DMS impact on the aromas of great Bordeaux red wines.
The aging bouquet of a great red wine is fascinating, but the least well-known phenomena in enology. It is the result of oxidation and other complex transformations which occur in the wine during bottle storage often resulting in a more complex and balanced bouquet. In addition, once the bottle is opened, the bouquet continues to change rapidly until it is consumed.
One of the key components of the ageing bouquet of red wines is the presence of DMS. A recent study found that among a large set of Bordeaux red wines aged between 10 and 20 years, those considered to have the best, or more typical, bouquet were found to have a much higher concentrations of DMS compared with the wines considered to have a less typical bouquet. In these aged red wines DMS was found to contribute to the wine with aromatic notes of truffle, undergrowth and hay. The same truffle notes were found also in Syrah wines with relatively high concentrations of DMS.
The concentration of DMS is also impacted by the terroir in which the grape is cultivated: DMS is higher where the temperature is warm and the soil has a moderate water deficit and a high nitrogen level. Moderate water deficit and high nitrogen status are characteristics of many Bordeaux terroirs. This is how truffle notes are often considered typical of great aged Bordeaux wines.
DMS impact on the fruity aromas of quality red wines.
Besides contributing notes of truffle, undergrowth and hay to a wine's bouquet, DMS was found to enhance the sweet fruity notes of red wine, and in particular of the blackcurrant aroma. This has been confirmed by several studies. DMS cannot be considered a direct compound of a fruity aroma, since it does not present fruity aromas itself, but it indirectly contributes to the expression of fruity aroma.
DMS in Beer.
A high concentration of DMS in beer is considered a defect. However, in lower concentrations it is acceptable in lager beers. A high concentration of DMS can be caused by problems in the production process or by infections. It presents itself with notes of cooked corn, cabbage, green beans, asparagus, tomato juice.
5 facts to remember about DMS.
- It contributes notes of truffle, undergrowth and hay to the ageing bouquet of great red wines.
- In low concentrations, it enhances the fruity notes of young red wines.
- In high concentrations it gives an "off" flavor (notes of cooked maize, tomato and asparagus).
- It increases with bottle ageing of wine for up to 10-15 years.
- It is typical of aged Bordeaux wines.
Additional reading:
- "Involvement of Dimethyl Sulfide and Several Polyfunctional Thiols in
the Aromatic Expression of the Aging Bouquet of Red Bordeaux
Wines"- Journal of Agricultural and Food Chemistry.
- "Olfactory impact of dimethyl sulfide on red wine fruity
esters aroma expression in model solution" - link here