In just three decades since 1990, average alcohol levels gradually increased by about 1% ABV across some of the world’s best-known fine wine regions such as California and Bordeaux.
This shift can be attributed to the association of wine quality with grapes that have achieved complete phenolic ripeness, potentially resulting in a greater alcohol content, and to the warming climate, which leads grapes to develop increasingly higher amounts of fermentable sugars. This trend has raised concerns, including worries about its potential impact on the distinct characteristics of certain wine styles, consumer well-being, and market demand too. Studies show that younger Americans display a tendency to reduce their alcohol intake, and might therefore choose a lower-ABV option over a higher-strength one.
Producers have adopted a variety of approaches to tackle the challenge, however, many come with drawbacks, whether practical, related to taste, or to consumer expectations. A common viticultural solution consists of harvesting the grapes before they have a chance to accumulate excessive amounts of sugar, but this can affect the quality of the wine. Reducing alcohol levels through enological strategies, such as vacuum boiling and membrane filtration, present even more intricate challenges, often washing away fruit, tannin, and flavor at the same time.
The industry has instead turned its attention towards an alternative solution: the use of low-alcohol yield yeasts. “In our hot Southern California climate, high brix levels and the resulting potential high alcohol levels have been an ongoing concern for winemakers,” says Kristina Filippi, the winemaker at Wilson Creek Winery in Temecula, California, who has recently begun experimenting with alternative yeast types and strains beyond Saccharomyces cerevisiae. “My purpose in lowering starting brix is related to creating a balanced wine … a delicate dance between alcohol, acidity, body, tannin, and residual sugar. If one of those components is much higher than the others, a wine can come across as disjointed and unpleasant.” This approach offers numerous advantages: it tends to be cost-effective and straightforward to adopt for producers and, crucially, can potentially benefit wine’s organoleptic qualities, too.
Searching for Non-Saccharomyces Yeasts
The metabolism of Saccharomyces cerevisiae yeasts, whose effectiveness and suitability in wine fermentations are well-established, consists in the transformation of sugars into alcohol. To naturally limit the production of alcohol, researchers have therefore been looking at non-Saccharomyces strains, some of which might be capable of fermenting must to complete dryness and generating appealing flavors while also producing lower levels of ethanol.
David Castrillo Cachón, a researcher at the Estación de Viticultura e Enoloxía de Galicia (EVEGA-AGACAL), has worked on both Saccharomyces and non-Saccharomyces strains such as XG3 and Metschnikowia fructicola. “Studies on non-Saccharomyces yeasts are relatively recent … with the most relevant ones being from 2010,” he says. “Non-Saccharomyces were once considered undesirable as they could cause spoilage, were uncontrollable, and generated higher concentrations of unpleasant aromas.”
Yet, the industry’s perception of non-Saccharomyces yeast has shifted as a result of the growing popularity of “indigenous” yeast cultures—often featuring non-Saccharomyces strains—and, crucially, more academic research on the subject.
“Part of our work has focused on the regional biodiversity of yeasts obtained directly from the surface of grapes and natural musts, and from natural fermentation of both conventional and organic musts,” says Castrillo Cachón of his work at the EVEGA-AGACAL. “Most of them are non-Saccharomyces yeasts, some of which have a metabolism that can … produce less alcohol.”
He explains that developing efficient lower-alcohol yeasts proves challenging as some non-Saccharomyces species, while yielding less ethanol, can’t complete fermentation independently. They typically need to undergo sequential fermentation with Saccharomyces cerevisiae, which tends to outcompete and eliminate them after inoculation.
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As reported in a 2016 paper, the inoculation of non-Saccharomyces species Starmerella bombicola and Metschnikowia pulcherrima—sequentially inoculated with Saccharomyces cerevisiae—can achieve a reduction of up to 1.6 percent ABV compared to the Saccharomyces cerevisiae-only control sample. The same year, the Australian Wine Research Institute reported that Saccharomyces uvarum, alone or in combination with Metschnikowia pulcherrima, yielded less ethanol, yet the resulting wine showed negative sensory attributes.
A further study, whose results were announced last year, demonstrated how non-Saccharomyces yeast Starmerella bacillaris utilized in sequential inoculation with Saccharomyces cerevisiae can reduce alcohol yields during fermentation by up to two percent, while still producing faultless wines. Developed by French enological products firm Sofralab as Starbella Low Alcohol, the yeast was due to be commercially available this year. Yet, Arnaud Soulier, the international marketing director of the Sofralab Group, says that the firm is undertaking further, larger-scale testing. “We have been working on it for three to four years by now, and we are still working on optimizing the process for its use,” says Soulier.
Is Aerobic Fermentation the Answer?
To minimize alcohol production during fermentation, the Institute of Grapevine and Wine Sciences (ICVV) in Spain’s Rioja has been focusing on a particular type of metabolism called respiration, applied to both Saccharomyces and non-Saccharomyces strains.
“The winemaking process is usually anaerobic,” explains Pilar Morales, an ICVV researcher who’s involved in the study. “Our proposal is to have an aerobic fermentation, which allows yeast to respire—breathe—the sugars. When sugars are fermented anaerobically, we get ethanol and CO2, but if they are respired, we get CO2 but no alcohol.”
Morales’ team found a Saccharomyces strain that, used in aerobic conditions, developed up to three percent less ethanol than a Saccharomyces yeast working without oxygen. “This process requires one inoculation only, so it’s easily manageable for a cellar,” she says.
Despite promising results in the laboratory, AZ3 Oeno, the enology consultancy firm working with Morales’ team, found that adapting the solution for commercial winery use still faces considerable hurdles.
Jesus Jimenez, pictured above, is the technical director for Bodega Numanthia and is researching the effects of Lachancea thermotolerans. Photo credit: Bodega Numanthia.
“We worked on scaling at different levels to develop an industrial process that could work in a winery,” says Gema Serrano, the innovation facilitator at AZ3 Oeno. “From the results obtained in the technological and process viability studies carried out in the wineries, it was concluded that it is necessary to continue researching … to find viable solutions.”
The latest research from the ICVV team shows that a Saccharomyces and Metschnikowia pulcherrima co-culture can lead to a whopping alcohol reduction of four percent ABV. “With the developments we published in our latest paper, we think it will be easier to make it scalable and commercially viable for a cellar,” argues Morales.
A Potential Research Breakthrough
In July this year, enological products firm Grupo Agrovin announced one of the most promising projects in the field to date. Agrovin’s yeast, belonging to the non-Saccharomyces Lachancea thermotolerans family and marketed as Viniferm NS Chance, provides lower alcohol levels and regulates pH and acidity of musts.
“There are other solutions and yeast available on the market, but for now Lachancea thermotolerans seems to be the best solution,” says Jesus Jimenez, the technical director at LVMH-owned Toro producer Bodega Numanthia. “It seems really good because it helps keep the wine in balance.”
Jimenez conducted trials on part of the 2022 vintage, using Lachancea thermotolerans samples from two suppliers. He observed positive results when the yeast was introduced either alongside Saccharomyces or a few days before. The wine involved is currently aging in barrels and will be used for blending and eventual commercialization once it reaches maturity. Meanwhile, Numanthia is also undertaking further trials with the current vintage.
“We will be doing five vinifications using the same parcel and different yeast combinations,” says Jimenez.
With the favorable feedback on Lachancea thermotolerans and the promising advancements in other approaches involving non-Saccharomyces strains and alternative fermentation techniques, a solution to regulate alcohol levels in wine may be on the horizon.
“Today, it’s very easy to find 16 percent ABV wines in Toro,” says Jimenez. “If we can manage to keep alcohol levels at 15 percent here, we’re good. And given our trials, I’m very hopeful about the future.”
