Commercial Yeast: Threat or Menace?

Mea culpa

For twenty years now, wine professionals in both production and the trade have allowed the Natural Wine movement to drive the wine marketing bus without a license. Most of its proponents have never actually made wine and have simply invented their doctrine out of whole cloth, based on premises that are now thoroughly road tested and debunked.

The prime doctrine of the movement, the violation of which immediately disqualifies a wine from consideration, is the inoculation of a must with commercial yeast. This is based on the mythical notion that true terroir expression can only occur when the fermentation is conducted by yeast from the vineyard. The geological term for this is autochthonous, which means “originating in the place where found.”

To be fair, the belief is not implausible. Bear in mind that for eight millennia of winemaking, nobody had the slightest idea what the mechanism of fermentation might possibly be. As late as 1872, Professor Pierre Pachet, Professor of Physiology at the University of Toulouse, declared Louis Pasteur’s theory of germs “a ridiculous fiction.” The transformation from sugar to alcohol in wine and beer has been utterly mysterious ever since the dawn of civilization.

When it comes to wine fermentation, there is only one genus that can complete a fermentation beyond 10% alcohol: Saccharomyces, a genus that came into being over 100 million years ago. There is no question that strains from the wild vinified the first wines. However, it is extremely difficult to isolate Saccharomyces from vineyards, where many other yeasts and bacteria, most intolerant to alcohol and low pH, proliferate in their millions.

In the last hundred years, yeast companies like Fleishman, Red Star (and its subsidiary Lallemand), Anchor and Laffort have busied themselves selecting, breeding and hybridizing super-yeasts with robust specialized capabilities. What has changed in today’s vineyards is that these yeasts overwhelmingly predominate. What’s more, commercial yeasts can set up shop in any winery microbiome environment that suits them. They arrive on the feet of insects, workers and tourists as well as many other sources unrelated to actual purchase.

The result is that “the place where found” is not the vineyard but rather the winery. A brilliant ETS study published in 2016, “The Natives Are Restless,” harvested fruit from six Oregon Pinot Noir vineyards which were then vinified at six wineries that had never purchased commercial yeast. PCR analysis on the resulting wines showed that all six wines at each winery were fermented on the same yeasts, but little similarity was seen in the strains found in lots from the same vineyard vinified at different facilities.

Additionally, small batches of grapes were shipped directly to ETS for micro-vinification. For the most part, these failed to complete AF due to the lack of Saccharomyces from the vineyard, further confirming the paucity of the genus in vineyards. Exhaustive swab studies at the ultramodern research winery at UC Davis nevertheless confirm that once they set up in wineries, commercial strains persist in adequate numbers despite draconian attempts at sterilization.

This is not to say vineyards no longer contain local strains that can be isolated given sufficient time and money. Impressive work at Opus One by ace microbiologist Sydney Rogers proved it can be done. She managed to isolate and purify novel strains from their estate vineyards that weren’t in anyone’s commercial strain database. Since other subspecies have likely taken up residence in the facility since its inception in 1979, Sydney ensures that the house bugs do the deed by growing up large batches for prompt inoculation, leaving the natties to ponder whether this violates their commandments.

Having otherwise dispelled the myth of vineyard-borne yeast under normal conditions, there remains to the winemaker to choose a path. What works in one winery may not work across the street. Joel Peterson of Ravenswood successfully avoided inoculation for three decades, producing sound, fine wines owing to a combination of cellar practices and good fortune that fostered a positive microbiome in his facility.

In some cases, a unique house microflora can become a signature stamp. It is said that San Francisco sourdough bread is unique because of the city’s specific microbial ecosystem, where a symbiotic relationship between the bacterium Lactobacillus sanfranciscensis and indigenous wild yeast thrives in the cool, humid coastal fog. The unmistakable pumpkin aroma of Château La Gaffelière is surely due to a resident microbiology seen nowhere else and survives through some mysterious collaboration of vine and cave. This is one way to speak of terroir.

On the other hand, consider the story recounted by Virginia’s legendary Jim Law of Linden Vineyards at a 2014 symposium. Jim has three Chardonnay vineyards from very different soils. For his first ten years, no inoculations were performed on these ferments, but when it dawned on him that they all tasted the same, he switched to a neutral commercial yeast that permitted the vineyard characteristics to display themselves. A house style was the last thing Jim wanted, thus a notion of terroir diametrically opposite from that of the châteaux of Bordeaux.

One aspect of uninoculated fermentations (or “feral ferments,,” as the Australians call them) is that they take a few days to get going, during which time, a variety of vineyard-borne bacteria and non-Sacch. yeasts such as Torulaspora, Kloeckera, Pichia, Candida and Brettanomyces have an opportunity to add complexing nuances which can be positive but are something of a gamble I personally would rather avoid. Part of my concern is the high levels of allergenic amines these bacterial incubations produce. This activity can be held in check by introduction of the commercially available killer yeast Metschnikowia pulcherrima, to which Saccharomyces is immune. But then one is left to wonder what was the point of the delay.

One thing that freaked out the early natural wine movement was the rash of outrageous claims in commercial yeast catalogues that their products would impart distinctive characteristics. Never having made wine, Ms Feiring and her ilk took these blatant falsehoods at face value while experienced winemakers chuckled at their naiveté. Ralph Kunkee instructed us in 1980 that the differences we observe early on were due to the production of acid-labile esters that would disappear within a year, and therefore we should choose or yeasts based on physical factors such as cold intolerance (to permit us to arrest fermentations), low foaming (permitting less messy in-barrel fermentations) and alcohol suppression, (enabling long, slow red fermentations at elevated temperature).

Times have changed. In recent years, commercial yeasts with enduring characteristics have emerged. Today we can choose between a flowery, high thiol rosé and a fruity, high ester version. Terpene aromatics in Riesling and Muscat can be enhanced. We can reduce titratable acidity. We can enhance red fruit aromatics in reds, a godsend when a little smoke character needs masking. Other red yeasts can convert harsh, astringent tannins into smooth, oily, supple tannins supporting aromatic character. There is also a fleet of commercial non-Saccharomyces with sundry magical properties.

These tools make tastier wines that receive higher scores and medals and sell more readily. So shoot me.

But now, Feiring’s point must be taken more seriously. The issue is no longer whether these yeasts actually work (now they do) but whether we will burn in hell if we use them. It’s a slipperier slope than it used to be. I think a woman should feel free not to shave her armpits, but I also think she has the right to do so if she so chooses. Can my profession be granted the same courtesy?

Today’s winemaker has many tools unavailable a decade ago. Along with these new yeasts, I include flavor-liberating enzymes and oak in its various forms. In the hands of a skilled artisan, their use need not obscure terroir, just as when cosmetics are properly applied, you can’t tell he’s wearing any.

Randall Grahm’s distinction between vins d’effort and vins de terroir need not apply. Sometimes it takes a lot of effort to become invisible. If the hand of the winemaker is apparent, that’s just bad cooking. But neither is raw food the pinnacle of haute cuisine. Rather than trying to legislate morality, consumers should choose leave the cooking to the professionals and reward with their patronage those who do it well and are forthcoming about the tools they use and why.