Submitted for San Diego SommCon:
**SommCon 2022**
**Outline for Seminar:**
**Microbial Terroir:** **Adjacent Vineyards and Singular Wines**
**A Guided Tour of Modern Microbial Science in California Chardonnay and Pinot Noir**
**Players:**
**Wes Hagen:** Moderator/Presenter. WSET 2, Nationally Recognized Wine Lecturer, author/petitioner of 4 American Viticultural Areas, Production Viticulturist and Winemaker for 25 + years.
**Geoff Labitzke, Master of Wine**, Kistler Vineyards. Panelist and presenter of 2 Chardonnays from adjacent vineyards that show uniqueness, even with similar climate and dirt.
**Will Costello, Master Sommelier,** Bien Nacido/Solomon Hills Estate: Panelist and presenter of 2 Pinot Noirs from the Estate program that show uniqueness even with similar soil and climate.
**Presentation Guide:**
**Opening remarks**: Wes Hagen, using a short slide show, will go over the current state of the science of microbial terroir, bacteria, fungi and the limitations science has to define these newly discovered markers of wine microscopy.
Using data and narratives from Drs. Ian tattersall and Rob DeSalle’s ‘Natural History of Wine’, Yale Univ. Press, 2015, Wes will present current understanding of microbial terroir:
· At the turn of the 20th C, two microbiologists, Martinus Beijerneck and Sergei Winogradsky, realized microbes were ubiquitous in our environment and profoundly impacted and affected many natural processes, not just diseases, which were the focus of much early ‘germ theory’ microscopy, started by Pasteur’s study of fermentation.
· ‘Microbial ecology’ is the study of how the microbiome impacts agriculture, nature and bodily processes of organisms from a grapevine to a Blue Whale.
· There are two main issues in studying the microbial influence on wine. One is technology. The expense of the powerful microscope necessary to observe the DNA and protein in a single bacteria cell prevented study until the last 15-20 years.
· Researchers use a fresh or saline water wash on wine grapes (to capture the microbial life on a single cluster) can then try to culture microbes from it. But even now, scientists haven’t figured out how to culture between 95 and 98 percent of all bacterial species.
· We know that a grape wash, from any vineyard’s ‘microbial ecology’ is 20-25 times more complex than we can determine in the lab.
· DNA sequencing is catching up! NGS, or next generation sequencing, can break the double helix by heat, check the sequence of a single strand, and confirm the structure will always ‘zip itself back up’ when it cools with complimentary and standardized by guanine making a chemical bond with cytosine, and thymine with adenine. This process can identify large numbers of DNA sequences in a grape wash: 500-10,000 for traditional sequencing, and 400,000 to 10 million unique microbial sequences, which shows great hope that this burgeoning scientific analysis is ready for a leap forward in data and understanding. We can add each identified DNA marker/microbe to a compendium of bacterial DNA sequence information found in winegrape wash, and start building our knowledge of microbial terroir as we mature scientifically.
· This microbe census will be unique for each microbiome/vineyard, and unique even from vineyard block to block, and certainly even from vine to vine or cluster to cluster, with higher levels of continuity expected as we increase proximity and identical varietals/accessions.
· Three major kinds of microbes are found living on the surface of winegrapes: filamentous fungi, yeasts, and bacteria. The strains of microbes do tend to show more commonplace overlap on the same varietals and locations. Microbial wash from the vine leaves also shows a whole different array of unique bacteria/fungi that do not colonize the grapes, and the soil’s microbial life is far more complex and varied, and deserves its own seminar.
· Using NGS, Nicholas Bokulich of UC Davis found that bacterial communities on the skins of Cabernet Sauvignon , Chardonnay and Zinfandel in Napa, Sonoma and the Central Coast showed both regional and varietal correlations. In other words, there are specific microbes, mainly bacteria and fungi, that tend to colonize in specific places and on specific grapes. (Show slide of this study)
· The researchers found that the microorganisms found in must — freshly-pressed grape juice, before fermentation — can be used as biomarkers to predict which metabolites will be found in the finished wine. Metabolites are chemical compounds that help shape the flavor and texture of a wine.
· The best studies we have right now show about a dozen recognizable microbes on Cabernet skins, with no idea how many were missed, and the same soil where it grew contained more than a thousand (again the actual number could be in the tens of thousands). So there is hope we can start correlating microbes and wine styles, and certainly understand that only very specific microbes prefer the environment of grape skins.
· To keep this discussion focused, I have described the question of how microbes that end up IN THE MUST are influencing wine flavor and ‘somewhereness’. But a question that might be more ably answered by soil scientists, is how do soil microbes impact viticulture: skin thickness, nutrient exchange and viability, water uptake, berry size, hang time, phenolic development? As we are talking about wine in the glass, I open that discussion up to our panelists when they discuss their vineyards and soils, but the focus here is how microbe populations regionally cluster around certain varietals and regions.
The BIG QUESTION: How does this new knowledge change the way we look at terroir?
· Piano, piano! Relax and let’s have a drink. With science catching up, we will hear and read about microbiomes in the vineyard more and more frequently.
· A key contributor to wine *terroir* is the grape microbiota. Specific members of the regional microbial communities guide alcoholic fermentation (AF) producing metabolites that affect the wines’ sensorial characteristics and quality. The process of fermentation is dynamic, leading to modifications in microbial diversity ([Wang et al., 2021](https://www.frontiersin.org/articles/10.3389/fmicb.2021.726483/full#B83)).
· A study in 2021 in Cyprus showed bacteria was more prevalent and expressive in fermentation kinetics and quality, and that fungi populations were severely reduced in fermentation much more commonly than the bacteria, which were more likely to thrive.
· Genetic markers have been found to identify specific populations on Cyprus grapes and in the resulting wines, and have been defined to the point where the authors see this as a way, in the future, to identify and classify microbial terroir, help classify its influence on ferments and flavors, but also identify genuine or faked wines from a specific region.
· Acknowledging our limited ability to scientifically define the influence of microbes in grape must and wine, using our ability to taste and take notes, to understand the wines organoleptically, and to come to consensus about regional characters, will give us future insight to correlate with the new developments in microbe DNA study.
· This is meant to be complicated because it is. We are at an amazing crossroads of science and human evaluation of wine. We can be amazed and thrilled at our temporary ignorance, and do what we can to build the strength of our shoulders so future wine scientists, consumers and sommeliers can utilize our discernment in the traditional study of wine, varietals, and regions
***Tasting and Discussion:*** ***TBD, the following reps and wines look like they will join, but not guaranteed.***
**Geoff Labitzke, Master of Wine, Kistler Vineyards**. Panelist and presenter of 2 Kistler Chardonnays from adjacent vineyards that show uniqueness, even with similar climate and dirt.
Geoff may focus his presentation and tasting of these wines as he and the brand seems fit, and will hopefully comment on what he thinks drives terroir on these sites.
**Will Costello, Master Sommelier,** Bien Nacido/Solomon Hills Estate: Panelist and presenter of 2 Pinot Noirs from the Estate program that show uniqueness even with similar soil and climate.
Will is free to focus his presentation on the brands and wines in whatever way he sees fit, but we will discuss traditional determining factors of terroir, and how we might
Wes will guide the conversation back to terroir, and what we can learn and what is still mysterious about these wines.
Wes will elicit questions and comments about the presentation and wines, and leave time for Q&A at the end.
Needs:
4 wine glasses and a tasting mat. 1-2 extra Somm(s) for pouring would be helpful.
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Thoughts? Suggestions?
Dining and Cooking