03.31.2017  
 

Innovation and Technique with Wine Yeast

The catalyst to winemaking is also key to style and a means of innovation for winemakers

 
by Andrew Adams
 
wine yeast chimney rock
 
Winemaker Elizabeth Vianna tastes through samples of Sauvignon Gris fermented with different types of yeast at Chimney Rock Winery. Viana views yeast as a component of the finished wine and experiments with a couple of new varieties each vintage.

Napa, Calif.—In 2002, the Terlato family that owns Chimney Rock Winery planted Sauvignon Gris near Rutherford, Calif. The location is thought to be one of only two sites growing Sauvignon Gris in Napa County. But that’s not the only thing that distinguishes Chimney Rock’s Elevage Blanc, a white wine that blends the Terlatos’ Sauvignon Gris with Sauvignon Blanc from the same vineyard.

The blend is comprised of more than 40 barrels, and several of these are used by winemaker Elizabeth Vianna as small-lot fermentations to experiment with new yeast strains. Vianna uses each vintage as an opportunity to trial yeasts she thinks may bring a specific aroma, flavor or texture to the wine and improve the blend overall. “I’ve been on a quest for guava,” Vianna told Wines & Vines during a tasting of her trial wines earlier this year, “and I think I found a yeast for that.”

That particular yeast was VIN13, a hybrid designed to boost aromatics by releasing large amounts of thiols during fermentation. Each vintage Vianna uses a core of about six to eight yeasts and tries one or two different ones.

Building components for a blend
Yeast is an elemental component of wine, and which strain to use can be one of the most important decisions a winemaker makes in perfecting his or her style. Each year suppliers unveil new strains and hybrid yeasts and yeast-derived products to help fermentation. These innovations are the focus of a recent Product Focus report in the April edition of Wines & Vines.
 
Each of Vianna’s trial wines tasted quite different and it might even challenge an experienced taster to be wholly confident they were in fact the same wine.  “You have to think of these as components,” she said. “The final wine doesn’t taste anything like the blending components.”

Some of the yeasts she uses are well known and often used for Chardonnay. D47 and CY3079 are sturdy fermentors, and Vianna likes D47 for its citrusy flavors and aromas, while CY3079 (which is often used for barrel fermentations) helps establish sufficient texture on the palate to balance the impact of oak. Other strains, like Laffort’s Zymaflore X5, can provide even more aromatic impact by producing high levels of thiols that lead to aromas of boxwood, citrus and tropical fruit.

While the Sauvignon Blanc and Sauvignon Gris come from the same vineyard, the grapes are picked over a period of a few days. Fermenting them with different yeasts provides Vianna a range of blending components. She doesn’t agree with the point of view that using such yeasts is not a true expression of the terroir of the vineyard. “Just because it’s an Alsatian yeast doesn’t mean it’s going to be an Alsace wine. Ultimately the goal is to make great wine.”

Ensuring purity of expression
Steve Matthiasson has earned commercial and critical acclaim for his line of wines from vineyard sites throughout Napa Valley. Matthiasson describes his wines as restrained, balanced and generally lower in alcohol.

One then might expect him to also use native fermentations, or to allow for spontaneous fermentations, but Matthiasson produces his wines at the custom-crush facility Bin-to-Bottle in Napa, where if he left his must to ferment naturally it most likely would ferment from the workhorse yeasts floating around the winery.

“Our experience in busy custom-crush facilities is that there are very fast and aggressive fermenting endemic yeast strains, and when we don’t inoculate our own fermentation, the resident strain ferments our fruit way too fast and hot,” he said.

Matthiasson prefers a “nice slow and cool fermentation,” and he inoculates with a specific strain so that the fruit and vineyard will shine through in the finished wine. “The yeast catalogues are hard to decipher. What does “enhance varietal character” mean?” he asked in an email to Wines & Vines. “We aren’t looking to enhance anything, we just want a nice clean and neutral fermentation that doesn’t get too hot or go dry too fast, and doesn’t produce strange, generic or off aromas—a yeast that would basically act like an indigenous yeast fermentation that we would get if we were in our own facility.”

After several years of trying different strains, Matthiasson settled on Clos by Lallemand. He said it generally starts well and then ferments dependably with the Brix falling by 2° to 4° per day. “It ferments slowly and steadily, and the wines seem very distinctive: true to the variety and the vineyard, not bulked up or generic in any way.”

Skip the hydration step
Innovation in yeast is not limited to strains and breeding. Windsor, Calif.-based ATPGroup is the U.S. distributor of French yeast supplier Fermentis, which is developing a line of yeast called “Easy to Use” that do not require the lengthy process of hydrating and making sure the yeast solution is at the right temperature before being added to the must. “This has been something they’ve been working on for a while in response to industry feedback,” said David Douglas, senior director of the science and technical division of ATPGroup.

Fermentis is now looking to patent revisions to its culturing and drying processes that enable it to produce dried yeast that is ready to ferment without needing to be rehydrated. The company is going back through all of its strains to confirm they can market them as “Easy to Use.”

Douglas said the rehydration process requires extra water, staff time and is vulnerable to error. A properly hydrated yeast could be added to cold juice and fail from temperature shock. Or, a distracted cellar worker could add DAP to a yeast solution. Simplifying the process also means less trained staff could perform inoculations with the same expectation of success.

“You get much less opportunity for mistakes.…But you get the same or better fermentation,” Douglas said.

Tips on ‘going native’
Nova Cadamatre, director of winemaking at Constellation Brands’ Canandaigua facility, was one of the speakers on a panel discussion about yeast at this year’s Unified Wine & Grape Symposium in Sacramento, Calif. Cadamatre said a wine’s price and market position are factors to consider if one is thinking of experimenting with using different strains. The right yeast, for example, could be an affordable and efficient way to boost the aromatics of a value-priced white wine, but a top-tier red from a well-known vineyard may only require a clean and efficient fermentation.

Yeast can be used to influence a wine’s aromatics, the speed of fermentation, completeness of fermentation, reductive elements, mouthfeel and the speed of autolysis. How the yeast can affect these elements of a wine, however, are in turn impacted by the cleanliness of the grapes, availability of nutrients, if the fruit was harvested by hand or machine and how long it took them to get to the crush pad.

Cadamatre recommends “cautious experimentation” with yeast to determine what works best with a particular vineyard. “A winemaker’s goal should always be to make the best wine possible, but it is only through thorough but intelligent trial and error that they can learn what it will take to do that,” she said in an email.

Going “native” or using spontaneous fermentations may sound great, but Cadamatre suggested asking if one’s customers even care, and if the risks of a stalled, sluggish or incomplete fermentation are worth not inoculating. The general rule she offered was “the better the fruit, the better the native fermentation.”

A less risky way to experiment with native fermentations is to allow a spontaneous start and have a backup strain ready to add at 16° to 18° Brix to ensure a successful completion.

Another practical example in her presentation included using Epernay 11, which is described as providing “slow, steady and clean” fermentations, and then finishing with VIN 13 to help aromatic development in white wines.

Cadamatre said winemakers should be willing to experiment and not limit themselves to exclusively native fermentations or a few strains they trust. “Where I do end up seeing tension is when a winemaker puts a limitation on themselves such as only using native yeasts or only using a specific strain of cultured yeast and not having room to experiment beyond those limitations,” she said. “Don't put limitations on yourself. Let the fruit tell you where the limits are through your own discovery.”

 

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