How to avoid the production of sulfur off flavors in red grape varieties with high reduction potentialPubliée le 19/07/2019 13:59
Some red grape varieties, such as Shiraz, Pinot noir, Merlot or Tempranillo, have a certain trend to express sulfur off flavors and reduction characteristics. These characteristics mask the red fruit aromas and thus have a negative impact on wine.
To tackle this issue and bring a new solution to winemakers, Lallemand Oenology, Montpellier SupAgro and INRA Montpellier have collaborated and designed an innovative selection technique for yeast.
A new QTL yeast strain to target grape variety with high reduction potential
With this collaboration, Lallemand Oenology, Montpellier SupAgro and INRA Montpellier were targeting the production of red wines with low level of unpleasant sulfur compounds, SO2 and acetaldehyde in varieties known to have the risk of producing negative reduction and sulfur off flavors like Shiraz, Pinot noir, Merlot and Tempranillo.
A patented innovative selection technique
To develop this new yeast, an approach of direct breeding, the QTL strategy, was used, targeting the following main phenotypes: low H2S, low SO2, low unpleasant sulfur compounds and low acetaldehyde production.
The strain was obtained through the directed transfer of two genes identified as responsible for the control of the sulfur assimilation pathway by backcrossing cycles.
The innovative selection technique has been patented: “Method of control on the production of sulfites, hydrogen sulfur and acetaldehyde by yeast”.
Double-checking for low H2S production
Once the yeast was obtained, its low H2S production was double-checked and confirmed with various tests on plates (Grape Juice Lead Acetate) and in fermentation conditions (Lead Acetate Strips).
Many trials were carried out in 2018 with this new selected yeast in various wine regions (Spain, Italy, USA and France) and in different wine conditions, mainly with varieties well known to have sulfur off flavor production risk (Shiraz, Merlot, Pinot noir or Tempranillo) but also with other red grape varieties (Grenache, Dolcetto, Incrocio Bruni).
The yeast showed a very good fermentative performance: alcoholic fermentation was fast and clean with excellent implantation. Almost no VA was produced and its tolerance to alcohol is high.
Besides, the trials allowed to demonstrate that the yeast has an excellent MLF compatibility.
The sensorial profile of wines produced with this yeast, which has low nitrogen requirements, expressed bright red fruit, no amylic aromas. The wines produced had very clean aromas and a soft and round mouthfeel. As far as sulfur off flavors production is concerned, in all the trials carried out, reduction was never perceived even when the control wine showed certain off flavors characteristics. The yeast presented a clear trend to have lower total SO2 (with the same free SO2), at the end of AF. It shows that the yeast has a unique property in that it will not produce SO2 during AF and also non-perceptible amount of H2S.
Lalvin Persy™: The first selected natural wine yeast for red to not produce SO2
For this new vintage, Lallemand Oenology is proud to launch Lalvin Persy™. When using it for the alcoholic fermentation of Shiraz, Tempranillo or Pinot noir grapes, wines will fully express their varietal aromas, avoiding the mask of H2S off flavors. The fruity characters are enhanced, the crispiness and aromatic persistency optimized.