WIN reached out to winemakers to find out more about how they’re finding and using wild yeast.
By Kathleen Willcox
For millennia, the process of alcoholic fermentation was shrouded in mystery. Fruit was left alone in covered containers; at some point, it would start to roil, roll and bubble. Solids were removed, and then, presto! A complex beverage emerged, which we know today as wine.
While vintners of yore couldn’t name the acting agents in the process, through close observation, they learned what seemed to work and how to guide it. For centuries, supernatural forces were credited for the transfiguration.
Then a Dutch tradesman and naturalist by the name of Antoni van Leeuwenhoek came along in 1680 and directly observed yeast cells through the high-quality magnifying lenses he invented. Two centuries later, Louis Pasteur expanded on his discovery, hypothesizing that yeast — not God — fermented wine, and that the type of yeast in the mix could drastically alter the end flavor of the wine. The race toward the understanding and controlling of the process of fermentation began.
Herman Müller completed the next leg of the race in 1890, when he successfully began producing commercial yeasts that vintners could rely on if they wanted more dependable, predictable flavors and aromas in their wines.
While most winemakers — about 80%, according to several estimates, including Jamie Goode, who took a deep dive into the subject in Authentic Wine: Toward Natural and Sustainable Winemaking — still use commercial yeasts to ferment their wines as insurance against funk, others see wild yeast as an essential ingredient in pure, terroir-driven wine.
The process of sourcing the best eukaryotic micro-fungus for your Pinot Noir can be a fraught process, seemingly requiring a blend of art and science akin to a magic spell. We’re nowhere near the finish line in the marathon toward the precise control of fermentation that still transparently reflects terroir, but we are certainly in an interesting portion of the race. We reached out to winemakers to find out more about how they’re finding and using wild yeast to holistically and completely translate the terroir of their growing site into their finished wines, without allowing the process to go off the rails.
Yeast + Grapes = Wine. How?
Before we take a walk on the wild side with vintners, a primer. It is not possible to see yeast with the naked eye, and yet they’re everywhere.
When grapes come into the winery, they’re covered in yeast. About 1,500 wild yeasts have been identified, but there are probably hundreds, if not thousands, more; the ones we need to worry about are classified as Saccharomyces or non-Saccharomyces species. The most common yeasts present on grapes coming in from the vineyard are Kloeckera apiculata and Hanseniaspora uvarum, according to research from University of California.
“Those yeasts are very sensitive to alcohol, so as soon as alcohol is generated, which happens when yeast eat sugar and create carbon dioxide, they die off,” says Morgan Beck, winemaker and general manager at biodynamic winery Johan Winery & Vineyard in Rickreall, Ore. “If you’re working with wild yeast, at that point, Pichia and Candida, which came in on the grapes in smaller amounts, are among the primary yeasts that take over, until the alcohol level hits about 10%. At that point, if you’re looking at Saccharomyces cerevisiae, which can tolerate higher amounts of alcohol.”
Saccharomyces cerevisiae was the first eukaryotic genome to be completely sequenced, and several hundred strains have been identified, with dozens and dozens currently commercially available for winemaking.
Evoking Fleuroir
“I was at an incredible dinner made with all Chilean ingredients, including edible flowers,” says Cristián Vallejo, winemaker at VIK Winery in Millahue, Chile, of the moment he had an epiphany on wild yeast. “It was so exciting to taste how all of the elements came together, creating complex flavors. I started thinking about how I could create a wine that was completely from our estate, without anything from outside of our vineyards and fields.”
That led to a deep examination and transformation. VIK Winery now ages wine in amphorae sourced from clay found on the estate, and in barrels toasted with fallen wood from the estate.
“We have a 4,000-hectare [9,884 acres] private park, and most of the estate is untamed fields filled with wildflowers,” Villejo explains, adding that only 10% of the estate is under vine. “Flowers, I discovered, have an extremely high concentration of wild yeasts, and a wide variety of them, too.”
Villejo decided that, by bringing in a sampling of the flowers from all over the estate, drying them and creating a tea that they could spray on grapes in the field, they could impart terroir through flowers — fleuroir — to the wines.
“Already we have discovered two new yeasts present on the grapes that come in that were not present before,” he says, adding that VIK partnered with the Universidad Católica de Chile on a study.
The 2022 vintage was the first to include fleuroir in VIK’s Cabernet Sauvignon, Carmenere and Cabernet Franc, and Villejo says he detected a new level of complexity, elegance and expressiveness in each of them.
The Bucket Method
Some vintners with less acreage to work with are using an ancient French technique for harvesting wild yeast. The method is gaining excited contemporary adherents in the New World, each of whom have a slightly different approach.
“It’s called ‘pied de cuve,’” says Johan’s winemaker Beck. “It translates to ‘kick of the tank.’ It’s a kind of kickstart or revving of the engines during fermentation. We have done this since 2005 with our first vintage. I wouldn’t even consider making wine with cultivated yeast, because it takes away from the expression of the place, which is the whole point of winemaking. From what I’ve tasted, it also produces more generic wines. With Pinot Noir, it’s all about sexy red fruits. Native yeasts do that, plus turn up the floral and spice characteristics along with umami and vegetal elements.”
Beck says that the Pied de Cuve method also curtails the risk many associate with native ferments.
“I understand that it feels scary, especially with Pinot Noir, which is so finicky and susceptible to bacteria that can take the fermentation sideways,” she says. “And sometimes, the process of gathering wild yeast in a bucket in our prized plots feels silly. But it works.”
The team places healthy grapes plucked from their most prized blocks into a sealed bucket, and lets it sit in the vineyard, where more than 22 cover crops (including yarrow, birdsfoot trefoil and self-heal) are grown.
“We give them time to absorb a wide variety of native yeasts, and then we literally dump that bucket of grapes — after a careful sensory analysis — into the tank,” she says. “That helps control the fermentation and deliver the good yeasts we want.”
Another Pied de Cuve Convert
More and more, George Nosis, owner of Atwater Vineyards in New York’s Finger Lakes AVA, has been exploring native yeasts via Pied de Cuve.
“We started experimenting with native yeasts with our orange wines in 2015,” he says. “We have a 30-gallon, sealable tank that I add plants to from all around the vineyard. We have chicory, several types of wildflowers, grape leaves, wild bergamot and hibiscus that I throw in there and feed periodically. We then inoculate the wines to eliminate the dangerous lag time right before fermentation, when bacteria can grow.”
As long as you eliminate that lag time, he says, you don’t face the “VA bomb” that so many hardcore adherents of commercial yeast fear.
“We don’t do anything here just so we can put it on our label,” Nosis says. “We did trials and taste comparisons, and we determined that [this process] actually makes better wines. The flavor is more complex, but the biggest difference for us is in the texture.”
Since 2015, Nosis has transitioned the orange wines, pet-nats and reds. He’s currently in the process of transitioning all of the whites to native fermentations; Riesling is currently fermented with commercial yeast, but will likely be fermented with native yeasts shortly.
Bringing in Wild Yeasts From the Wind
Sun, water, aspect and soil are considered essential components of terroir, but Scheid Family Wines vintner Casey DiCesare sees wind — and the yeasts it brings — as another integral contributor to wine’s character and flavor. When Scheid created Metz Road, DiCesare began exploring the impact of wind-blown native yeast.
“The yeast blowing in the winds down the Salinas Valley into our Riverview Vineyard influences the fermentation,” DiCesare says, explaining why he chose to focus on this vineyard for Metz. “The location of the vineyard is extremely special, on a cool climate shelf above the Salinas River, across the valley from Santa Lucia Highlands. We set up a shipping container right there in the vineyard to do the fermentation and take advantage of the native yeasts within the vines.”
The approach — as romantic and whimsical as it sounds — is rooted in science.
“We’ve analyzed our yeasts through VNTR [multi-locus variable copy number tandem repeat analysis] DNA fingerprinting from ETS Laboratories,” DiCesare explains. “We’ve identified non-saccharomyces yeasts including Torulaspora delbrueckii, Metschnikowia pulcherrima, Pichia species and Candida species at the start of our fermentations. Each contributes varying amounts of precursors for unique aromatics, along with mouthfeel building blocks such as mannoproteins and polysaccharides. Following the non-saccharomyces, we typically see 2-3 saccharomyces yeast early fermentation, 8-16 saccharomyces yeasts mid-fermentation and 4-12 saccharomyces yeast at the end of fermentation.”
The magic and mystery, DiCesare says, “is in the biodiversity through the life of a fermentation.”
Next up? DiCesare is considering exploring yeast sourced from bee hives located in the Hames Valley Vineyard.
Once you step onto the wild side, it seems, it’s hard to turn back.
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Kathleen Willcox
Kathleen Willcox writes about wine, food and culture from her home in Saratoga Springs, N.Y. She is keenly interested in sustainability issues, and the business of making ethical drinks and food. Her work appears regularly in Wine Searcher, Wine Enthusiast, Liquor.com and many other publications. Kathleen also co-authored a book called Hudson Valley Wine: A History of Taste & Terroir, which was published in 2017. Follow her wine explorations on Instagram at @kathleenwillcox
