Zurich’s Rauschling wine: proof of a genie in the bottle
ZURICH, SWITZERLAND – A live yeast discovered four years ago in an 1895 Rauschling wine from Obermeilen, canton Zurich, will provide the world’s winemakers with an exciting new option in 2013. The yeast, which plays an important role in developing a wine’s nose, or unique natural perfume, is already proving its real value to Zurich area winemakers, researchers at the Agroscope federal research station say. Beautiful wines from a new generation of the yeast are starting to win awards.
Next year, sales outside Switzerland begin. The yeast can be used with many grape varieties, not just Rauschling, and it’s already shown its worth for sparkling wines and distilled eaux-de-vie.
The 1895 yeast wines are now coming of age, recalling the wines that once made the area around Zurich famous. One hundred years ago this was still Switzerland’s largest wine region; today it is the fourth in size, thanks in part to urbanization.
Zurich discovery is “unique” in world
Perhaps more importantly for world wines, the new bottles are the proof of the genie in the bottle, for the Zurich experience is “unique” in the world of wine, says Juerg Gafner of Agroscope, who led the project. Gafner says that nowhere else in the world has a live yeast been found and successfully grown from a very old vintage wine.
The research that was part of the Agroscope project is also forcing some rethinking about yeast, one of the most intriguing areas of current wine research.
The 113-year-old yeast discovery came about after a small group of winelovers opened a “Meiler 1895″ bottle at the Schwarzenbach family’s Reblaube winery one evening in 2008 and discovered that it had remained surprisingly fresh. The bottle was part of a vertical (different vintages) tasting session and several of the others were also surprisingly well maintained.
The rest of the 1895 bottle was quickly put into a sterilized jar and rushed off to the federal research station on the hunch that some of the yeast that accounted for the beautiful taste and aromas might still be alive.
Wine yeasts can tell us much about terroir, aromas and the vintage
Wine yeast is a complex business: yeast is essential to turn grape juice into wine, but several types of yeast are involved at different stages of the process. Those that cannot survive high alcohol levels, for example, may be present during grape ripening but they die off during the fermentation process, when other yeasts become more active. Some are critical for developing good aromas while others play a more negative role. The yeast, particularly those helpful ones that give wines their distinctive aromas and impart part of what we know as terroir, generally die off as the wine develops, creating the lees, or sediment.
One type of yeast is Saccharomyces cerevisiae, a main fermentation agent. A study of wine yeast and bacteria species published in 2007 in the International Journal of Vine and Wine Sciences by University of California Davis noted that “S. cerevisiae was detected only in bottles of recent vintages.”
Agroscope’s confirmation of this yeast, live but dormant, in a 1895 wine, marked a turning point.
Alive but in need of resuscitation
Agroscope found 13 colonies of S. cerevisiae from three separate layers of the yeast in the 1895 wine, a success rate that encouraged them to look further.
Their dormant yeast-hunting expedition turned up 12 other old vintages from 1897 to 1962 that had yeast, but only two years, 1935 and 1962, gave them the precious S. cerevisiae. The others had colonies of another yeast, Candida stellata. The researchers at the Swiss centre, whose research is carried out in Nyon and Wadwil, found that this yeast was in wines from years that were humid and cold.
S. cerevisiae, on the other hand, appeared in years that were good vintages, climate-wise.
Discovery saving Swiss wine cellars
If that were the end of the story, there would simply be a rush on rare bottles of Rausling from the good years, but the research didn’t end with the discovery of an old dormant yeast.
Agroscope scientists discovered the “how” of the yeast’s survival: yeast in a bottle will find another source of energy, rather than glucose, if its survival depends on it.
Research now shows that it can be used to avoid or correct a costly problem in cellars when fermentation stops at the wrong point. The unplanned stoppage can cause a wine to have unwanted residual sugar that ruins it, but S. cerevisiae can correct this.
Daniel Fuerst from Hornussen was seducedby the yeast, after working with it in 2011 to repair a problem with his wine. He then used it in 2012 with 8,000 kg of Pinot Noir must, the juice that is starting to ferment. “It gave me beautiful, fruity wines with remarkable, rich aromas.”
Sparkling wines and distilled beverages get “1895” results
Technically speaking “1895” has good sales potential for sparkling wines and distilled beverages as well as still wines. The yeast produces only one-third the biomass of most wine yeasts, a bonus for any wine, but particularly useful during the delicate disgorgement (sediment is ejected from the neck of the bottle, under pressure) process for champagnes and other sparkling wines.
Eaux-de-vie benefit as well, a group of 24 judges confirmed at a 2011 tasting session by the Swiss Fruit Union: the yeast keeps the fruit up front. “Fruity, fruitier, the fruitiest!” is the enthusiastic final word from Sonia Petignat-Keller, Agroscope’s distilled beverages specialist.