Carbonic Maceration vs. Whole Cluster: What’s The Difference?
07/01/2014
Grapes getting ready for fermentation...
First off, apologies to my reader, I know this may be a little longer post than usual and maybe too technical, but lately it’s an issue on which I’ve seen some interest.
It seems to me that many people, from the casual drinker all the way to the seasoned wine journalist, use the term “carbonic maceration” interchangeably with “whole cluster fermentation.” I asked some friends who are also winemakers and they too have witnessed this phenomenon.
These terms are not interchangeable.
Traditionally we associate carbonic maceration with French Beaujolais, particularly Beaujolais Nouveau which is released every year just after harvest and right before Thanksgiving. These wines are usually light bodied, very fruity, lacking in depth and aside from some off aromas perfectly drinkable.
Recently, I came face to face with the confusion. I was with some friends who had recently bought a place out in southwest Sebastopol. This area really is a Mecca for fantastic Sonoma Coast Pinot Noir! Now my friends do have a small vineyard on their new property. Sadly, when they said small, they meant it. The 150-vine site is too small even for us here at R2 Wine Co., but I did assure them I’d be more than happy to help them with their winemaking this year.
As we were removing all the extra shoots and leaves from the base of the trunk the other day; we got to talking about winemaking style and how we’d vinify the grapes that would come off their site. I recommended they do a big saignée (another upcoming blog topic!) and I recommended that they do some whole cluster fermentation, maybe as much as 50 percent.
This was where the confusion showed itself. “We really don’t want to do carbonic maceration,” they let me know. I said I did not want that either, and tried to explain the difference. I did not succeed. Their final word on the subject was “Yeah, but we’d like a really intense a focused rich wine, it seems like all those wines made via carbonic maceration are watery and light.”
Groan!
Let me try again.
The biggest similarity between carbonic maceration and whole cluster fermentation is that both use intact clusters in the ferment. The most fundamental distinction between the two processes is oxygen or lack thereof.
During carbonic maceration an anaerobic environment is created by blanketing a sealed fermentation vessel with CO2 (usually in the form of dry ice), thus denying the resulting fermentation any air. The resulting fermentation occurs in an oxygen-free environment. While breaking down the sugars in the grapes without oxygen the yeast also begins breaking down malic acid, one of the main acids in wine grapes. The result is a less acidic and fruiter wine than in a traditional fermentation.
Interestingly, in this anaerobic fermentation style, yeast can not digest sugar as the alcohol levels increase, and instead, turn towards the acids in the grape, and convert these into alcohol, resulting in a wine that has less acid and some residual sugar remaining. The finished wine may see the final acidity level fall 3.5 grams per liter. If you think that your average Pinot Noir is commonly in the 6.5 grams per liter, you’re getting wine with half the acid than you might have otherwise.
It should here be said that complete carbonic maceration, in such an anaerobic environment is rare. For the most part, a winemaker going for this light and fruity style of wine would shovel the grape clusters into a closed top or sealed fermentation tank with good old normal air in it. Then the weight of the grapes then crushes the clusters on the bottom. The resulting juice then begins fermenting in the traditional way: Juice, yeast, air. This creates CO2, which then tapers off the traditional fermentation and results in carbonic maceration of the remaining grapes.
Generally speaking, the resulting wines are very fruit, light in acidity and short lived.
In whole cluster fermentation there is a certain percentage of whole clusters present during the initial stages of fermentation. That percentage is a winemaking decision based on the style of the wine the winemaker is trying to achieve.
Because, more and more it’s becoming clear that there really isn’t a “typical” fermentation style, I can only say what I usually do and why. I typically leave anywhere from 10% to 75% of the grapes intact; that is I don’t de-stem them. I do this because I think it creates a slower and colder fermentation. This results in more nuanced and intense aromas in the final wines. Also, I really like the slight earthy flavors that these stems add to the wine.
It is this combination of colder ferments and flavor/aroma contribution that leads winemakers to use whole clusters in their wines. However, the colder fermentation can be a mixed blessing and thus is a delicate balance. The colder the ferment the less extraction you’re going to get. So if once used too much whole cluster, and the resulting fermentation never really got above 85 degrees, the final wine might have very little pleasant fruit flavors. Inversely, if the fermentation gets to hot, then the yeast might actually die off before fermentation is complete (uh-oh!). Or I would risk losing a lot of the pleasing aromatics that tend to dissipate as the fermentation gets into the mid to high 90s.
The general rule of thumb used to be that the greener the stems the less a winemaker was “supposed” to incorporate them into the wine. I’ve found that not to be the case, and I think that more and more people are also—through trial and error—finding this to be the case as well. In fact, many times, I’ll get more of the green, “stemmy” flavor from clusters that are riper and actually have more a more tan or brown color than neon green stems.
Ultimately, there is a big difference between Carbonic maceration, and using whole grape clusters in the wine. I hope this slightly too long jotting has begun to both illustrate the difference between the two and also to describe why a winemaker will use whole clusters in her winemaking and what these whole clusters contribute to the final wine.
Wines, especially Pinot Noir, can benefit greatly from whole cluster fermentation. The process can enhance a wine’s earthiness and berry flavors and make for a much more complex wine.
Have I helped or confused the situation further? Let me know…
Cheers!
Drew Huffine
Winemaker
Post By:
Drew Huffine