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What Really Happens With 'Native Yeasts'

Recent revelations put conventional wisdom into a different light
Photo by: David Yellen

Posted: Dec 1, 2015 2:05pm ET

"Our industry gets so stuck in lore," laments Ken Wright. One common idea the Oregon winemaker has challenged involves native yeasts.

Conventional wisdom once warned that less robust yeasts that come from vineyards on the grapes might cause incomplete fermentations, but that long ago proved to be unfounded. Winemakers let their fermentations begin spontaneously to get smoother textures and complex flavors. But just what do those native yeasts do?

Savvy winemakers know better, but the myth persists that it's the yeast from the vineyard that completes an "indigenous" fermentation. It's not.

Wright and five Oregon colleagues actually studied what was present in their Pinot Noir vineyards and in their fermentation tanks. Rich DeScenzo of ETS Laboratories, who conducted the tests, found anywhere from one to 19 different yeast strains in samples from six Willamette Valley vineyards in the 2014 vintage. Most common were hanseniaspora and pichia; metschnikowia was also prominent. No commercial yeasts were added, but midway through all fermentations ETS found only strains already present in each individual winery, all of them Saccharomyces cervisae, the strain responsible for commercial yeasts.

"No matter what, the yeast in your house performs the fermentation," Wright says. That's not surprising. Non-saccharomyces yeasts are less tolerant of alcohol, usually petering out when the alcohol level hits 5 or 6 percent.

"Even if you add yeast," Wright adds, "in the middle of the fermentation that yeast you added is gone, out-competed by the house yeasts that are there all the time."

For years, rather than dispose of the settlings from fermentations through the town system, he sprays them over his Savoya Vineyard, where it apparently loses out to the only reportable strain in his vineyard: hanseniaspora.

ETS found significant numbers of a commercial Williams-Selyem yeast strain in Wright's winery. "Over the years I inoculated with it a lot," Wright says. "And now it's become part of my native population in the facility. All that stuff I've added at Savoya has had no effect. I need to spray my facility down with the yeasts that I want.

"If I were building a new facility, I would be washing that place down with the strains I love."

For different reasons, another Oregon winery has found a way to exploit indigenous yeasts' tendency to convert sugar to alcohol less efficiently. At Chapter 24 and Maison l'Envoyé, Burgundian winemaker Louis-Michel Liger-Belair employs techniques to encourage non-saccharomyces yeasts early in the fermentations, before they fall by the wayside. The winery reports drops in sugar concentration as much as 4 to 5 degrees Brix before any alcohol was measured in the musts. It could be native yeasts at work early in the fermentation.

With less sugar to ferment when saccharomyces takes over, Chapter 24 gets lower alcohol levels in finished wines, even when picking the grapes fully ripe. Tasting blind, I find a spaciousness and transparency in the structure and texture that allows rich flavors to float serenely.

A Pinot Noir world of rich, ripe flavors without intrusive alcohol? Sounds like nirvana to me.

Harvey Steiman
San Francisco —  December 2, 2015 1:21pm ET
Several winemakers emailed me privately with questions about this study.

One, who has never used commercial yeasts, asked if the result presupposed commercial yeasts were used. Saccharomyces cerevisae must be present to complete a fermentation, and that's what floats around in the air and survives in the winery. The Williams-Selyem strain happens to be part of the mix of S. cerevisae strains identified in Wright's winery. DNA tests identified other Sacchoryces cerevisae strains in other wineries.

The others involved in this study were Beaux Frères (Grand Moraine Vineyard), Bethel Heights and KWC (Savoya 777 House Block), Cristom (Eileen 114), Penner-Ash (Lillies) and Solena (Hyland).

Another vintner expressed astonishment at Chapter 24's reported drop in Brix before any alcohol showed up in the fermentation vats. That strains credulity for me, too, but that's what they said. In any event, some of Chapter 24's 2012 wines clocked in at less than 13 percent alcohol yet showed the ripe flavors of wines at 14-plus. Something is working there.
Louis Horta
Regional Lisboa, Portugal —  December 2, 2015 1:33pm ET
I am conducting native fermentations in a small boutique production scale in "Regional Lisboa", Portugal. In 2015 our 23 degrees Brix, across four Classic Bordeaux varieties blend resulted in 13.4 Alc., not measurably different from commercial yeasts. That said, I would like to mention that we may have a possible unknown yeast strain in the vineyards that protects the wine from oxidation. Our 2009, 75% Cabernet Sauvignon blend, can endure up to twenty days in a decanter without significant decline and still enjoyable. Will anyone, please, shed some light on what may be going on with my wine and, or the organically farmed vineyard. Total SO2 never exceeded 60ppm.

Thank You,
Louis Horta
Lyle Kumasaka
Arlington, VA —  December 6, 2015 9:37pm ET
In his book, "The Science of Wine,"* author Jamie Goode describes studies done by a Matthew Goddard on yeast strains at isolated New Zealand wineries. Goddard found that the dozens of strains of S. cerevisaie in a wild ferment at Kumeu River were unique, or at least genetically distinct from commercial strains. However, a strain found in a new oak barrel from France also contributed, so it wasn't entirely "indigenous." It appears as though S. cerevisaie exists in local forms that can become established and dominant even in the absence of cultured yeast.

Interestingly, Goddard found that S. cerevisaie was not present in the winery buildings or equipment pre-harvest, and also found S. cerevisaie in vineyard bark and soil, so concluded that the yeasts were indeed being brought in with the grapes. These findings and conclusions seem to be different from those in the Oregon study.

*This is an interesting book, by the way.
Harvey Steiman
San Francisco —  December 7, 2015 11:34am ET
"The Science of Wine" is an excellent book. I read it avidly when it came out.

One explanation for the Oregon study's finding no evidence Saccharomyces cerevisae in some vineyards there might be that that the populations are relatively small in the vineyards, but they are the only yeasts that survive in fermentations once they get past concentrations of 5 or 6 percent alcohol. And Saccharomyces strains are found in abundance in wineries up and down the west coast.

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