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Conversations with Carlo: whole cluster fermentation of Pinot Noir


Carlo Mondavi, whom I got to know and like last year in Kapalua, emailed to bring me up to date on his new project, RAEN, a Sonoma Coast Pinot Noir he’s making in collaboration with his brother, Dante.

Carlo Mondavi

His email prompted me to ask him some followup questions, which led to an exchange I thought is interesting enough to reproduce. The subject is Pinot Noir, and the role of stems in the fermentation.

Carlo had sent me this video of him and Dante making the wine. Along the way, Carlo says, concerning the whole-cluster fermentation he enjoys, “I can smell the greenness of these stems, they’re super-green.” My ears perked up at this, because I had thought that you don’t want green stems in the fermentation, you want brown, ripe ones, in order to avoid passing on that green, vegetal aroma and harsh tannins to the wine. So I asked Carlo, “If you whole cluster with green stems doesn’t that make the wine taste and smell green?”

He replied, “I…believe that the stems being green and thus under ripe or ideal is a complete misconception.” His response is worth quoting in full:

“In fact DRC and most of the best whole cluster examples are harvesting when the stems are electric green. This also means most likely and certainly for us that the sugars are lower and the extraction of bitter flavors will be lower. We also take into account sap flow…

“I believe that sap flow is greater in certain clones and in certain sites varying vintage to vintage… There is no perfect map so we go on taste and observation… To determine the amount of whole cluster vs destemmed fruit we ferment we run a quick tasting. We take the stem sans fruit, cut it up, put it inside a pastil bag and squeeze the sap out. We then observe the sap (how much, how sappy) then taste the sap to see how astringent it is. From there we make decide if we will use some, none or all of the whole cluster.…  This past vintage we certainly used a great amount of whole cluster as it was a new moon and the sap seemed to much less than what we might have seen on a full moon.

“Thirdly I also like the balance of bitter and sweet… Stems add potassium and tannin to a wine and can balance the overly strawberry, cranberry, rhubarb fruit flavors… to me it gives the wine a middle palate of velvet and structure and in some examples and slight elevation of minerality.

“Waiting for full brown clusters is a major mistake in my opinion… If you wait that long you are looking at harvesting well north of 25 brix of sugar and in December in some sites. This would yield a wine of incredible bitterness and a PH that would be certainly unfermentable and unstable naturally. With that said where we make our cuts is where the rachis meets the shoot this area is brown and lignified. We make our harvesting cuts right in the middle of this browning area to minimize sap flowing out into the juice.”

Still puzzled, I asked Carlo, “In a vintage like 2011, I found some coastal Pinots to have a green, minty edge. So, where does that come from?”

Carlo: “Huh… That’s a Good question. I would think some stems, the local terroir and for late harvesters, botrytis… I see a bit of botrytis each year… Pinot noir clusters are so tight it just seems to happen when the heat comes after the rain or In some vintages with the humidity…  With that said green can be no stems with green seeds or Rosie’s, tough under ripe skins or jacks… I have tasted de stemmed and 10 percent whole cluster wines and found them be more green than 100 percent whole cluster wines depending on the site and vintage… I also enjoy wine that can have a slight green note… I don’t see green to be bad so long as it is not over the top… Just like anything.”

I’ve never felt that whole-cluster fermentation is better than destemming, or vice versa. California Pinot Noir can be delightful either way. I do feel, as does Carlo, that stems can give Pinot Noir a fuller body and more tannins, not to mention spiciness. Still, I’m not quite convinced that green stems do not bring a green note to cool-climate Pinot Noir, and I’d love to hear the opinion of others.

This is one of the wine taster’s biggest conundrums: it’s easy to detect something in a wine but a lot harder to identify exactly what causes it. When I was a reviewer, I tried to avoid attributing specific results to specific causes, if I couldn’t be absolutely sure about the connection. Asking winemakers to explain can sometimes clear things up, but sometimes it can make you even more confused. Which is why I was always happy to leave the winemaking to the winemakers, if they’d leave the wine reviewing to me!

  1. Interesting, indeed–I can’t wait to read the responses. Re minty flavors, I’ve heard that attributed to eucalyptis oil from nearby trees, presumably airborne.

  2. Reading Carlo’s comments kinda scares me to tell you the truth. It is the natural simplicity in wine making that makes the wine beautiful. I grew up in Hungary where we did not have any means of stem removal so the wine was always 100% stem in. Therefore the fermentation was always cut short to avoid the bitter flavors the stems would release in higher alcohol. With technology spreading and able to remove the stems from the must we welcomed the extra time we can macerate to gain a LOT more flavor and fruit from the skins. One thing we are still not able to avoid is the green seeds in less than perfect years. Those have just about the same effect as the stems and can impart vegetative flavors (including mint) during fermentation. It is why the 2011’s are rather spicy and herbaceous and a bit lighter than usual. Tannin management is a challenge too in those years. If you ever chewed a green stem or seed you will know immediately what I mean. I little goes a long way.

  3. Csaba, your comment makes a lot of sense to me.

  4. David Vergari says:

    Belief system, pure and simple. But hey, he thinks that it works so who’s to argue, right?

  5. Great Article Steve! Thanks for introducing us to this video!


  6. Bill Haydon says:

    So, David. The plan is to haughtily dismiss it out of hand with the snide “belief system” comment without the slightest interest in delving into the science behind his arguments. I don’t know if the guy is right or not, but I find his position interesting and worthy of deeper analysis.

    It sounds to me like you’re the one clinging to a belief system that is utterly resistant to any challenges to its orthodoxy.

  7. New Moon, full Moon – I suspect the Moon is always up there in the sky, circling the earth. So I don’t see how a Full Moon would effect plants any different than a New Moon as respects sap movement caused by the gravity of the Moon, and we should know this because the Moon is not able to create tides in the Great Lakes nor the Mediterranean Sea, so it’s effects on sap is moot. Considering the average distance of the Moon from the Earth, let’s say 238,000 miles away, and the relatively small diameter of the Earth, 7,900 miles, there is about a 3% difference when the Moon is on one side or the other of the Earth. That’s not much of a difference. As for moonlight having an effect on sap, I have no idea, do you? I don’t think we can get rid of the Sun just yet.

  8. Jason Jardine says:

    Carlo hit the nail on the head in regards to SAP being absolutely the most important component in determining the use of whole cluster vs lignification. You can be fully lignified but depending on the vines cycle still have significant sap/moisture running through the stems and vice-versa. In regards to the moon, I would not discount the influence of light (and other “effects”) on the mobility of water/nutrients/ “sap flow” within a vine or any plant for that matter. It is widely known to sow seeds 8-10 days prior to the full moon which greatly enhances germination etc… Hard to argue with some of these time tested theories.

    Now, I will say that its just not that simple. Many factors other than sap influence the presentation of whole cluster within a wine. Fermentation temps, punchdown regime, time on stems, pressing, vineyard site, barrels, etc.

  9. David Rossi says:

    I wish I had the easy answer for this, but like most things in winemaking “it depends”. Since there is no universal answer, I will ferment a small bin of whole cluster separate from the destemmed grapes and use the resulting wine as a blending tool.

    I have definitely seen green flavors out of green stems and better results with more lignified stems. Ph definitely goes up and that can add some texture which I like.

    I have had whole cluster ferments that are harsh, tannic and green tasting and others where we get spicey notes, cooler fermentations and silky texture. Once I know a property and get in tune with what happens with different ripeness levels I will use stems accordingly.

    In my opinion, destemming is best until you get to know the impact they will have and what level of ripeness the stems should be at. Ah ambiguity… got to love it.

  10. Dan Fishman says:

    I don’t think I have ever seen fully lignified stems on Pinot Noir. In terms of flavor, I haven’t noticed much of a correlation between the color of the stems and the flavors imparted. In fact, some of my favorite whole cluster lots have had very green stems. I agree with Carlo’s assertion that stem inclusion seems to work better on less ripe grapes, as with very ripe fruit flavors I find the “stemmy” characteristic seems out of place and off-putting.

    I am also operating under a theory that 100% whole cluster actually leads to less stem flavor than,say, 50%. But I don’t have a good explanation for why that might be.

  11. Steve-

    Thank you for posting our conversation and sharing our first story about RAEN!

    I love the dialogue and wanted to share some of my thoughts.

    Clay- Thank you for your comment… I totally agree that the terroir or site is that largest element that leads to some wine having a eucalyptus or menthol characters. The air that flows through the forest fields and site surrounding the vines is what defines the native yeast and is an integral component of the flavors that develop in the wine during fermentation.

    Csaba- I agree with you in the sense that natural simplicity in winemaking is ever important today. That is just what RAEN stands for. Rainfalls upon our fields, the water filters through the rocks and soil down to our roots… the vine drinks. In the summer months the warm sun sweetens the water and ripens our fruit… as the cool ocean mist and air flows through the forest and fields it carries the cells that collect on the waxy bloom of our grapes creating the sites native yeast. In turn if we did nothing the berries would ripen and eventually in the late summer sun crack open mixing the sweet juice with the wild yeasts on the skin… without intervention fermentation would occur and the annual rain would turn into wine. Dante and I feel that our job as winegrowers is to evaluate when the balancing factors between, sugar, acid and tannin are at the ultimate level to make world class wine… We then ferment natively with no additions other than the bare-minimum SO2 and dry-ice for an initial cold soak. RAEN also means Research in Agriculture and Enology Naturally.

    John- This is one of my favorite topics and thank you for commenting about this as I did a poor job sharing my thoughts in my conversation with Steve… Admittedly this is really geeky and apologies if this does not read as fact as most of this is just a theory. The theory is that I believe that full moons or lack there of, changes most everything in nature. When thinking about it a full moon is indirect sunlight bouncing from the other side of earth and then back down showering the night with the suns energy. In theory if the full moon is indirect sunlight, plants could be metabolizing the subdued rays and photosynthesizing ever so slightly. If that is the case then the sap would be flowing a bit more vigorously rather than slowing or receding into the trunk on a moonless night. This has been proven in the ocean with algae photosynthesizing on a full moon but not in the vineyards. Even if the full moons presence holds sap-flow or ever so slightly increases sap-flow this would be notable to the cluster and fruit and if whole cluster is included in the fermentation notable to the final wine.

    Jason- Thank you my friend. You are one of the absolute finest vintners of our generation. Congratulations on your new role at Hanzell… Looking forward to tasting your first vintage there!

    David- I completely agree. Looking forward to tasting your wine as well!

    Thanks again Steve!

  12. Thank you Steve for sharing Carlo’s comments and video. We visit Continuum every year and were at the Continuum Summer Event in the Vineyard (2012) where Carlo and Dante introduced their wonderful blend -Novicium. They mentioned there was a Pinot Noir project in the works, so we have been waiting on details. Its exciting to see how this generation of Mondavis approach winemaking. Can’t wait until I get my allocation!

  13. The key word is sap.

  14. Derek Rohlffs says:

    My winemaking mentor Jeff Brinkman of Rhys Vineyards spoke on this topic at the Anderson Valley Pinot Noir Festival Technical Session a few years back and noted that he also often uses “neon green stems” as what is more important than the color is the dryness of the stem and whether or not it is still running sap. From a Waits-Mast summary of his comments: he said that he will use whole clusters of grapes if the stems are dry when chewed on and have a walnut quality to them.
    Jeff also pointed out that doing 100% whole cluster wine is dependent upon vineyard practices and that the types of grape clones used (he said that the Swan clone works well for whole cluster Pinot Noir) can have an impact. Additionally, he said that picking the grapes early is best when doing whole clusters and added that hand sorting of the fruit after picking is also critical.
    When fermenting the wine, Jeff does punchdowns by foot because he is doing 100% whole cluster fermentation and it’s impossible to use a punchdown tool as, during fermentation, the fruit is like concrete. He admitted that making 100% whole cluster Pinot Noir is “hard to do casually.”

  15. Hi Carlo, I like your explanation but as far as I can find out, vines do not photosynthesize Moonlight, it is 1/50,000 the intensity of sunlight. It’s too dim to be used for photosynthesis unless you happen to be certain types algae. Dim light might be helpful to orient oneself toward a underwater thermal vent, and this could be the origin of photosynthesis. Darwin was very interested in this subject, he wondered why clover leaves folded shut at night. What were they doing? We know now that moonlight is disruptive to plants circadian rhythms, so many plants avoid moonlight…if they can. My guess is even full moonlight falls far below the threshold to get the enzymes to draw CO2 into the stoma and work through all those enzymatic processes ending up with oxygen poop. That takes serious horsepower. It’s more reasonable to assume our vines don’t like moonlight at all, it messes with their rhythm.

  16. A quick point as I wait for a plane flight:

    It isn’t just about the % of whole cluster but also how you arrive at that percentage. I had two Pinots, from the same vineyard, side by side. Each had 40% whole cluster but one was much more defined by its stem character. Turns out that wine had one section fermented at 100% and the other at 0% and blended it down to 40%. The other was 40% across the board. So it isn’t just how much whole cluster but how you get there.

    Adam Lee
    Siduri Wines

  17. Judy Phelps says:

    Just another example of how significant a winemaker’s impact is on a wine. Sometimes we get so focused on terroir or vineyard source, we minimize winemaking as a source of differentiation.

  18. Paul Sequeira says:

    Very interesting. My take on the moon influence is that moon cycles affect sap flow, just as they affect tidal flow. Very interesting stuff.

  19. David Vergari says:

    Bill Haydon,
    Late to the party, just read your reply. Show me the science.

  20. Paul Sequeira, your comment makes me wonder why the 28 day moon cycle’s influence on sap flow would be more important than the daily one–the two high tides and two low tides that occur daily are perhaps reflected in sap flow?

  21. Bill Haydon says:

    David, I am neither a viticulturist nor an expert in biodynamic agriculture, and I’m not entirely sold on the latter. I was asking for the science–one way or the other–not professing to have it. I am open to learning more about its theories provided that its backed up with solid analytical thought. In other words, though skeptical of some aspects, I won’t dismiss it out of hand and want to learn more. There actually was a pretty thoughtful give and take on both sides which was instructive, far more so than simply dismissing Mr. Mondavi’s theories out of hand.

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