Yeast Q&A with Hanzell's Consulting Winemaker

First, please forgive the lapse in posting. I've been "out sick." Now, back to our regularly scheduled program... I read an interesting round-table discussion about yeast in a 2006 WineBusiness.com interview with Michael Terrien, Peter Anderson, and Larry Biagi. I had a few questions of my own about the role of native yeast in wine-making, so I contacted Mr. Terrien to get his thoughts. Michael is currently Consulting Winemaker with Hanzell Vineyards.

SLG: I've visited Sonoma and Napa during crush a couple of times and noticed that the entire valley seems to become saturated with the aroma of yeast at that time of year. I also noticed the same aroma coming off the nose of several wines I sampled there last October.

What can you tell me about how yeast affects the aromas in wine, and what do you make of this similarity I noted between the smell in the glass and in the air?

MT: Wine is made from grapes and yeast. Often, it is aged in barrels too. It should not surprise you to smell the aroma of yeast in the bottled wine, no more than finding it is possible to identify the ingredients of grapes and oak. The first responsibility of the yeast is to turn the grape sugars into alcohol. The wonderfully aromatic bi-products of this metabolism contribute to the identity of wine, from fruity esters to funky sulfides.

SLG: Are you aware of whether any study has been done in Sonoma County to determine which ambient yeast strains wafting through the valley during harvest/crush are dominant, and whether commercial strains are dominant outside of the cellar? If not, do you see such data as being pertinent?

MT: I am not aware of such as study in Sonoma, but Sonoma County is enormous and encompasses great diversity both in climate and soil type. If don't believe a survey of wine-yeast would turn up county-wide dominant strains that are any different than in other wine-growing regions, but it might be possible to isolate some unique ones. But I think I understand what you are getting at: have industrially-produced yeasts affected native fermentations outside the wineries that use them? I suspect so. This would only matter to those winemakers who claim their wines are unique because of the yeast.

SLG: How big a factor do you think yeast is compared to other factors such as soil, in the outcome of the final product in terms of flavor and complexity?

MT: Yeast can and do influence wine flavor (as well as color and mouthfeel) to some degree, but it isn't usually the only source of difference. An extreme counter-example is a wine that has fermented with a yeast called Brettanomyces. The aromatic compounds resulting from such spoilage can be truly disgusting, with a bouquet of horse manure. But by and large the results of fermentation with the acceptable wine yeasts in the Saccharmoyces family are modest in comparison. In my experience there are far more influential factors on a wine than the yeast: vineyard and vintage are both readily apparent in a wine more so than yeast; and certainly farming practices such as leaf-removal or winemaker decisions such as whole-cluster maceration or the proportion of new oak can be observed in the final wine while the yeast choice is at best a point of speculation.

SLG: Why do some wine-makers choose to ferment with various native strains separately and then blend later? What limitations do you see with that technique?

MT: Each fermentation vessel, be it a tank of barrel, is its own unique environment. The native flora resident in the inside surface of the vessel, or residing on the grapes will compete for the nutrients in must. Some microbes will defeat others, and flavors will diverge from what one might assume casually are identical fermentations. With these divergent fermentations a winemaker has more 'ingredients' to work with when it comes time to assemble the blend. This level of attention is more likely associated with making small batches of wine. It is not scalable.

SLG: Please tell us a little bit about your wine-making philosophy and the main differentiators between your philosophy and the philosophies at both ends of the spectrum from zero manipulation to consistency through science.

MT: Hanzell has a well-deserved reputation for cellar-worthiness, both for the Pinot Noir and Chardonnay. The philosophy informing the winemaking techniques through the five decades of Hanzell's history has always been in service to this reputation. I think it is particularly fascinating to understand just how technologically inclined and innovative Hanzell's founder James Zellerbach and his winemaker Brad Webb were in the 1950s when they began.

Bob Sessions, who made the wines at Hanzell for 30 years up until quite recently, embraced the science and chose to honor his forebears by only carefully diverting from their practices. The implications are intriguing in many ways, but take this one subject of yeast: Hanzell's Chardonnay has always been inoculated with an isolate from Montrachet. The sensibility of craftsmanship would seemingly be at odds with the use of just such an industrially-produced yeast. However, at the time of Hanzell's first vintage in 1957, the goal was to reproduce the singular flavors of Burgundy, a feat that had not been accomplished in California.

Their foremost pursuit was to make a wine to compare favorably with the Grand Crus. Only one or two wineries in all of the New World were pursuing this goal and certainly no market demand prevailed to differentiate their wine from their competitors by native fermentation.

A little more background on Michael Terrien: After UC Davis, Michael joined Acacia where he worked for nearly a decade before going to Hanzell. Now, he has a number of clients he consults for on winemaking while circling a close orbit around Hanzell. Before moving to California, Michael lived in Maine where he was born and raised.