‘Natural Wine’ Pt.2: A View on Native Yeast
There is a strident debate today concerning wines fermented with indigenous ‘wild’ yeast versus cultured ‘laboratory’ yeast. Those who argue for, and/or practice the former, valorize the wine’s ‘naturalness’ and champion terroir. (The Charter of the Association for Natural Wine states that, for its members, “only indigenous yeast directs vinification.”) Those who employ cultured yeast tend to dismiss the difference between ‘wild’ and ‘domesticated’, consider themselves pragmatists, not dogmatists – and, also, often champion terroir.
Everyone agrees that yeast forms flavor, but there have been few other agreements between the two sides.
Points of view:
• Speaking of their portfolio, this statement can be read on the website of wine importer Louis/Dressner: “All wines are made with the natural yeasts on the grapes, in the vineyards and in the cellars. Cultured yeasts to rush fermentation or add ‘enhancing’ aromas and flavors are unacceptable. We look for wines that express their terroir. No enzymes, no hormones.”
• “Yeast are yeast”, claims John Kelly, Sonoma winemaker: “The emphasis by the ‘natural’ wine movement on a distinction between ‘native’ and ‘cultured’ yeast is largely misguided and arbitrary.”
• In his recent book, Reading between the Wines (2010), my friend and esteemed wine importer Terry Theise wrote, “It sounds laudable to culture one’s own vineyard yeasts, but it has yet to be proved that it’s anything more than a seductive romance to assume yeasts are a crucial, inherent aspect of terroir.”
Two recent studies are clarifying the issue.
This summer, a team of researchers from the University of Florence conclusively proved, for the first time, that place-specific, indigenous strains of Saccharomyces cerevisiae yeast enjoy a year-long life-cycle synchronous with their site.
“Our findings indicate that wasps are a key environmental niche for the evolution of natural S. cerevisiae populations, the dispersion of yeast cells in the environment, and the maintenance of their diversity”, state the researchers, led by I. Stefanini and L. Dapporto. They determined that a portion of the growing season’s S. cerevisiae survive in the insects’ intestines through the winter, and the queen passes these unique strains – a signature of place – to the rest of the hive, and thereby, back to the growing fruit in the summer.
(S. cerevisiae is otherwise known as ‘baker’s yeast’ or ‘brewer’s yeast’; it’s the most powerful and important yeast in the fermentation process, and is critical to the transformation of grape juice to wine.)
Stefanini and Dapporto’s article was published in the Proceedings of the National Academy of Sciences (http://www.pnas.org/content/109/33/13398), and covered by the New York Times (http://www.nytimes.com/2012/08/07/science/dont-swat-that-bug-it-may-be-working-on-next-years-vintage.html).
(PARENTHESES 1: Cultured Yeast as Enhanced-Flavor Creator)
For millenia, wines have been crafted with the help of S. cerevisiae, along with some combination of over 1,000 ‘wild’ yeast strains like it, yet the final product of this ‘wild’ fermentation is not always predictable; temperature conditions in the winery, the size and material of the fermentation vessel, and the enzymatic composition of the juice, can slow or even stop the fermentation process.
In the last several decades, our ability to scientifically isolate and employ ‘pure’ yeast cultures has resolved this uncertainty for most wineries around the globe, providing more consistency and control. Laboratory wine yeasts are isolated, developed, and marketed by companies like Lallemand, Phyterra, and Red Star’s Fermentis division; among other effects, these yeasts may “enhance spicy clove, nutmeg, and fruity flavors”; “contribute creamy fruit”; “encourage the fresh fruit aromas of orange blossom, pineapple, and apricot”; “minimize vegetal characteristics”, and much more. Lallemand alone offers over 100 of these yeast strains, in addition to enzymes, nutrients, and bacterias – and they’re widely used.
“Harnessing the power of nature”, is one way this business has been described.
For example, to help meet demand for their ‘fruity, aromatic’ Sauvignon Blancs, the New Zealand government spent six years and $9.6 million studying Sauvignon’s singularity, and succeeded in isolating the wild ‘Pichia kluyveri’ yeast strain in 2005 at Kumeu River. Grown on Petri dishes, and combined with S. cerevisiae, it “lifts the fruity zing” of Sauvignon Blanc from Auckland to Queenstown (http://www.newzealand.com/travel/media/press-releases/2008/3/08_mar_28_foodwine_discoverytorevolutionisewine_pressrelease.cfm).
(PARENTHESES 2: Cultured Yeast as Salvaged Harvest)
In his engaging blog ‘Notes from the Winemaker’, John Kelly (quoted earlier), a former biochemist, and current winemaker at Westwood Winery, gives a very reasoned argument for the use of cultured yeast (http://www.winemakernotesblog.com/2010/04/natural-wine-and-yeast.html).
He describes how fruit from two separate blocks from the same harvest ferment differently. In one, S. cerevisiae is strong enough to succeed the initial mix of wild yeasts to complete fermentation. In the other, a yeast strain named kloeckera apiculata (a major species on wine grapes, bearing a relationship to brettanomyces) typically dominates the fermentation, giving strong aromas of ethyl acetate (nail polish remover). In John’s words, “Simply, and brutally, if the Kloeckera dominates — the wine spoils. To make sure this does not happen, as a practical matter in lots where I detect strong ethyl acetate early in the ferment I always choose to inoculate with a selected strain of Saccharomyces. This response defines the difference between dogmatism and pragmatism.” Even the utmost care in the second block and/or the winery, he claims, cannot rectify the issue.
(PARENTHESES 3: Mental Disconnect)
‘Conventional’ knowledge in the trade: yeast strains live on the skins of mature grapes in the vineyard, yet these are not strong enough to carry fermentation through; they often die at 3% alcohol. S. cerevisiae is needed; if one isn’t lucky enough to vinify in an ancient cellar, with cerevisiae living in the walls’ seams, ceiling cracks and barrel surfaces – but still ONLY in the cellar! – a ‘pure’ strain must be introduced to bring the wine to over 10%, and to meet the winemaker’s (or market’s) desired flavor profile.
“Choose your yeast as you would choose a tool”
(Advanced Winemaking Basics, http://winemaking.jackkeller.net/strains.asp)
From this train of thought, a mental disconnect can result between the terroir in the vineyard and the reality in the winery. If a vineyard’s exposition, altitude, and soil drainage, added to a summer’s drought, humidity, or hail, only amounts to the harvest of as healthy fruit as possible, while the REAL creation of wine occurs scientifically in the cellar, then terroir can be rejected as a qualitative consideration to the finished wine.
But what if yeast were an integral part of terroir, as the studies quoted earlier seem to prove?
In 2010, for the World of Fine Wine (“Are Yeasts Part of Terroir?” Issue 29, 70-73), Dr. Jaime Goode spoke with Dr. Mat Goddard about his groundbreaking research earlier that year. “’This was the first demonstration’, Goddard states of his work, ‘that [yeast] strains in spontaneous ferments derived from the local environment.’”
In his research in the Kumeu River region of New Zealand, Goddard’s experiments showed the following: 1) ‘Wild’ populations of S. cerevisiae were quite different than escaped commercial strains. 2) These ‘wild’ strains did not exist on winery equipment or walls. 3) The strains in the wild ferments analyzed were brought into the winery with the grapes. 4) There are strains of yeast indigenous to particular geographies, particular terroirs, resident in the soil, tree bark, and flowers, transferred to the fruit by insects.
(Goddard’s research can be referenced at: Goddard, M.R., Anfang, N., Tang, R., Gardner, R.C., and Jun, C. (2010), A distinct population of saccharomyces cerevisiae in New Zealand: evidence for local dispersal by insects and human-aided global dispersal in oak barrels. http://onlinelibrary.wiley.com/doi/10.1111/j.1462-2920.2009.02035.x/abstract)
TRUTH OR TASTE?
Does it all come down to taste? i.e.: How much ethyl acetate is too much? How much “creamy fruit” and “spicy clove” and “minimized vegetality” is too homogenized? How much brettanomyces is too much? Some winemakers (and wine drinkers) are offended at trace levels; others find pleasure in wines with medium-high levels. What makes the flavor profile of a wine region ‘correct’? Can one taste a difference between three otherwise identical wines from… Gigondas, let’s say: one made with indigenous yeast, one made with cultured yeast, and one made with a mix of the two? Other than some sort of truth-valence, what does ‘native’ yeast bring to the table?
I couldn’t agree more with Terry that applying categorical moral judgements to wine are infantilizing. I do NOT want to say that ‘native’ yeast wines are inherently BETTER or more TRUE than ‘cultured’ yeast wines.
But I do know this:
• Working the grape harvest and outdoor crush pad for an organic winery in western Piedmont for 3 weeks in 2007, I watched – with an annoyance that quickly turned to wonder – the endless stream of bees, wasps, and other insects who flew from neighboring forests and flora to alight briefly on the newly-broken grape skins; they landed on the fruit, flew off again, and returned in a timeless cycle, ensuring a seamless fermentation.
• Alsace’s Olivier Humbrecht describing indigenous yeast fermentation in these (paraphrased) terms in 2010: “While it’s true that S. cerevisiae is what completes the fermentation, and that it is NOT the leading strain at the beginning, what’s most important to the complexity of the finished wine – and impossible, yet, to measure scientifically!! – is the rich mix of variable yeasts at work on the wine in the first hours and days of the fermentation process. Their effect on acids and enzymes at this point determine what S. cerevisiae will later have to work with. Consequently, they have a direct impact on the finished wine. With all we know, it’s still a mystery, and one we need to embrace.”
• The extra dimension of texture which indigenous, or ‘sponti’ (spontaneous) yeasts give the finished wine are undeniable, and are due in no small part to the effect of multiple variable yeasts initially at work. I find that the sooner colonizing S. cervisiae yeasts dominate the fermentation process, the keener, more primary, and swifter the finished wine will be on the palate; the more time it takes to ‘grab hold’, the wider range of impressions will be manifest to the palate.
It’s this ‘wider range’ to which recent studies point, giving greater possibilities to terroir expressions whose striking – and delicious – individual examples we’ll continue to offer at Telegraph.
(I look forward to the results of further researches!)
- jeremy quinn