Whole Cluster Fermentation: A Wild Card

In winemaking there are no absolute truths, no universal approach, no proven methodology. This is what makes wine so interesting, so variable in its expression, so endearing to the consumer. One man’s whole cluster triumph is another man's green garden atrocity. The use of whole clusters in fermentation is, as winemaker Michael Browne of Kosta Browne states, “A bit of a wild card depending on site and vintage. When it works it affects aromatics and flavors, sometimes in an earthy sense, sometimes in a vegetative sense, and sometimes in both ways. Some of the aromas and flavors I see are clean earth, green tobacco, unlit cigar tobacco, black or white pepper and snap peas. Sometimes even cologne or agave. I tend not to like the snap pea or green profiles.”

Michael Browne’s concerns are widely held, for the unpredictability of whole cluster fermentation can result in a wine that is herbaceous, vegetate or green. On the other hand, if the stems are mature and the clusters are never crushed, pumped or damaged in any way to avoid the release of juice from the stems into the wine, the resulting wine can be enhanced by whole cluster inclusion.

Whole cluster fermentation refers to the fermentation of intact clusters of grapes (Dijon clusters are pictured) as they are picked from the vine with no intervention of machines leaving all berries and stems (the part of the stem which holds the grapes is called the rachis) intact. Traditionally, red winemaking begins with crushing of the grapes to start to release the contents of the berries and de-stemming to remove the grapes from the rachis. A mechanical crusher/de-stemmer is often used. The stems are often removed in red winemaking before fermentation since the stems have a high tannin content and when unripe, stems can give the wine a green aroma due to extraction of 2-methoxy-3-isopropylpyrazine which has an aroma reminiscent of green bell peppers. With Pinot Noir, even if the clusters are de-stemmed, the grapes are usually left uncrushed (“whole berry”) to encourage the development of desirable aromas through partial carbonic maceration (fermentation within the grape coincident with fermentation of the juice which seeps out of the grape).

A recent tasting I did in the cellars of Freestone Vineyards with winemaker Theresa Heredia started me thinking about whole cluster inclusion and how it can affect the aromas, flavors and tannin structure of a finished wine. We tasted together three samples of 2008 Pinot Noir from barrel that had no stem inclusion (100% de-stemmed), 30-40% stem inclusion and 100% stem inclusion. I could clearly taste a step up in aromatic and flavor complexity with increasing amounts of stem inclusion along with a more bold and lengthy tannin structure. When ripe stems are properly managed, it was clear to me that their inclusion produced a superior Pinot Noir.

The Burgundians have practiced stem inclusion for centuries, as historically they had no de-stemmers. Today, many notable Domaines are advocates of whole cluster such as Dujac and Domaine de la Romanee-Conti. The New World has largely moved away from whole cluster fermentation or limit it to 10% to 30% of the clusters. There are, however, some devotees who use as much as 100% whole cluster in selected wines (Ambullneo, Freestone Vineyards, Native9, Tantara, and Windy Oaks among others) with favorable results.

I polled a number of prominent Pinot Noir winery owners, winemakers and a Professor at University of California Davis to ask them about their understanding of the contribution of whole cluster fermentation to Pinot Noir. None could elucidate the exact biochemistry involved as this has apparently not been clarified, but their responses shed considerable light on the role of whole cluster fermentation in Pinot Noir winemaking today. I have excerpted their comments for brevity.

Kevin Harvey, Owner, Rhys Vineyards “I have not studied whole cluster fermentation from a chemical standpoint. My evaluation of stems has been almost entirely organoleptic. I love the complex spicy, rose petal aromatics and soft silky texture. I do know that the whole berry fermentation and resulting intracellular fermentation produce the rose petal aromatic. In addition, the stems add some forest floor elements from the rachis which become integrated spice with time in the bottle. The tannins also differ in that stems contribute some tannins (which is often silky smooth midpalate tannin) while preventing the harsh seed tannin from being released since the grape remains encapsulated longer.”

Jeff Brinkman, Winemaker, Rhys Vineyards “ While I have never seen a biochemical analysis of whole cluster ferments, I think you could infer the presence of several groups of organic compounds. I would look into the terpenes, terpenoids and isoprenoids. As you know, the terpenes are responsible for the abundance of floral aromas in wine. My personal feeling is that since commercially terpenes are extracted from tree resins, especially conifers, the residual sap in stems may contribute some of the floral aromas and the distinct pine sap aroma that can be found in whole cluster ferments. Some of the floral aromas are not very different chemically from those that give pine sap their aroma. Another class of organic compounds, the acetate esters, may be involved as they form many of the aromatic compounds in wine. I don’t know any of this for fact, its just what I think about when I am laying awake at 3:00 A.M..”

Theresa Heredia, Winemaker, Freestone Vineyards “Like the grape skin, stems contain phenolic components, including tannins. Not removing the stems can help improve the phenolic structure of Pinot Noir since it is a thin skin grape and has little tannin naturally. The stems also contain pyrazines so if the stems are not ripe enough, they can cause herbaceous characteristics in the wine. However, the combination of the pyrazines and tannins, along with the many other natural components that stems contain, can add plenty of lovely spice characteristics to the wine. The riper the stems, the spicier the flavors. The greener the stems, the more herbaceous the wine can become. We pick with lots of natural acidity and lowish Brix so that the wine is 13.0% to 13.5% alcohol, pH 3.5 or lower. We always notice a better phenolic structure and complexity of aromatic profile in wines such as these, when we use at least a percentage of whole clusters. We only use whole clusters if the stems are beginning to lignify and only if they are relatively thin. In 2009, I opted to only do two 100% whole cluster fermentations because the stems were too thick, juicy and were not very lignified. I did use some percentage of whole clusters, though, with tremendous results. It is a challenge, but it can be done and the result is lovely."

Jim Schultze, Winemaker, Windy Oaks Winery and Vineyards “I have always liked an element of whole clusters in our fermentations, but our 100% Whole Cluster Pinot Noir release has been a real eye opener. Of all of our nine 2007 Pinot Noir releases, the 100% Whole Cluster clearly would have the most tannin, yet it is the smoothest and most approachable at a young age. I don’t think this is a coincidence!”

“Grape stems contain large amounts of phenolics, particular tannins and flavonols, and other flavor compounds. The key, though is physiological ripeness since immature stems can provide a significant hit of green flavors. While seeds also contain high amounts of tannin, it is hard to extract. Moreover, stems contain many other flavor compounds not found in seeds.”

“It is the unusual vineyard that can reliably produce physiologically ripe stems each year. When our fruit is starting to ripen, I taste the stems on a regular basis. I find that they hit a point where the tannic harshness disappears and is replaced by a very pleasant smooth flavor. Stems can then contribute these flavors to the wine.”

“Another dimension to whole cluster fermentation is prolongation of fermentation. I find consistently that our 100% whole cluster fermentations last much longer than our other fermentations. This past fall, our 100% whole cluster fermentations averaged more than 35 days, while our other fermentations (which were partial whole cluster) lasted around 30 days. I think the reason is that at the beginning of whole cluster ferments, some of the fermentation is taking place inside the grapes (carbonic maceration). Over time, the skins begin to break down and the juice is released, resulting in a more typical fermentation. I have also found that our fermentation temperatures are lower with the 100% whole cluster fermentation, no doubt extending the fermentation, but also resulting in a different flavor profile.”

Michael Browne, Winemaker, Kosta Browne “Whole cluster fermentation affects the tannin structure. It can be a subtle effect or quite grippy. When used as a blending component it can work very well concerning texture. I found when a bottle is allowed to age, the texture from whole cluster can add a dense velvety character, but when you omit whole cluster, this character can be a bit more aggressive. I ferment whole cluster as 100% whole cluster lots so I can then blend just the right amount into the finished wine. More popular now is to add whole clusters to the fermentation with de-stemmed fruit. Nothing wrong with this but this is not how I choose to ferment. I find the site has an impact on how the wine reacts as does the vintage. I test a few lots early in the vintage to see how the vintage will affect whole cluster ferments and I then adjust the rest of the program accordingly.”

Jeff Fink, Winemaker, Tantara “I am in the midst of assembling the 2008 Pinots and my palate is now acutely dialed into the merits and downside of stem inclusion. Starting with fruit selection, certain vineyards are better and more consistently able to achieve riper stems. That begs the question: What constitutes stem ripeness? The following things are important: (1) Color of the stem. We look for a darker green. Bright lime green indicates harsher and more astringent tannins, (2) Aromatics of de-stemmed stalks. We look for sweet rather than overtly herbaceous aromas, (3) Stiffness. We avoid rubbery stems, (4) Lignification. There should be preferably an inch of woody material where the stem connects to the vine. This can be more or less but the whole stem is never entirely lignified, (5) Where the berries connect to the stalk should have a dark color and the berry should be easily removed leaving little pulp. This is all linked to fruit ripeness but certainly there can be ripe fruit on under ripe stems. In the Central Coast, our extremely long growing season is certainly a benefit in helping to achieve stem ripeness.”

“What do stems bring to the vinification? We normally ferment about 10% of our lots with some percentage of stem inclusion. In our small fermenters that hold up to 1.5 tons or 3 picking bins of grapes we might add a bin of carefully sorted whole clusters and then cover that with a bin of de-stemmed fruit. This protects against the formation of volatile acidity that can occur in uncrushed exposed grapes. We will also do some 100% whole cluster ferments. These need to have a juice covering also and we release juice by the traditional method of pigeage or by foot. We harvest our grapes cool, then cold soak until they reach the temperature where fermentation naturally starts and we either inoculate with yeast or allow them to ferment on the native yeast. We find that whole cluster fermentations seem to ferment cooler, longer, and are markedly different in aroma and flavor. We think this is due to the significant amount of unbroken berries. The stems are the best vehicle for ensuring a higher percentage of whole berries. We notice no reduction in pigmentation and, in some cases, the wine may be darker following whole cluster ferment. The whole cluster wines can have more of a green and chalky astringency when young. For this reason, we tend to avoid stem inclusion from vineyards that produce naturally more herbal or tannic wines. In riper fruit, we think stems may avoid the production of higher alcohol and over ripe flavors but we have never quantified this.”

“I am a big fan of the things that whole cluster fermentation can bring to the finished wine. The aromatics can be thrilling and literally spine tingling. There can be a purity, depth and freshness to the bouquet that almost defies description. I suppose the case could be made that these wines are stylized. It could also be argued that these wines represent more of the site and are more minimalist.”

“We typically find that with new world palates it can be harder to achieve an acceptable balance of fruit, aroma and structure so we have never commercially released a 100% whole cluster Pinot. However, we do bottle them and as we evaluate how they age that could change. Also, our most expensive wine, Evelyn, has been the wine with the highest percentage of stem inclusion. This year our proposed final blend will be about 30%. Recently I finalized the 2008 La Colline blend and the addition of 2 whole cluster barrels in the blend made all the difference. Penetrating, almost haunting aromas and a very evocative wine. Tannins are there but soften with exposure to air. Most Pinot to me is lacking in the aromatics. It is the hardest component to capture. Clearly stems rock!”

“In conclusion, stem inclusion brings depth, texture, fragrance, age ability and that mysterious element of intrigue that all great Pinot should have and aspire to. In 2009, we vinified our first Garys’ Vineyard with stem inclusion. At this point the results are stunning both aromatically and on the palate. We plan to continue our study and evaluation of stem inclusion.”

Ted Lemon, Winemaker, Littorai “The most basic chemical fact is that when you add stems to a wine, you increase the pH and decrease the TA compared to a completely de-stemmed wine. The implication of this is obvious. If you add a large percentage of whole clusters, you may, depending on region, vintage and ripeness at picking, have to acidify the resulting wine unless you are comfortable with very high pHs. That is the downside from a chemical perspective.”

“There is a difference between just adding stems back (which basically no one does) and doing a percent of whole cluster, because, the whole cluster brings a dimension of carbonic fermentation to the resulting wine. Besides the carbonic effect, there is also the sensory effect of the stems themselves. They can lend aromas which range from vegetal to menthol to wintergreen to cinnamon and spices. Stems can also have a dramatic affect on flavors. They can lend astringency and bitterness. Perhaps the most interesting aspect of stems is their effect on the tannic impression of a wine on the palate. Some people claim that stems make a wine more tannic. I would argue the other way. Due to the increase in pH and the presence of a partial carbonic maceration, whole cluster wines tend to be softer than de-stemmed wines (depending on the region, vintage and percentage of whole cluster).”

“In summary, the effects of whole cluster fermentation are wide ranging and dynamic and reflective of the region, vintage and percentage of whole cluster. Over the years, my philosophy has evolved to the following:

1. If the vintage and region lends itself to some percentage of whole cluster, I like to use whole clusters. I find it adds an extra dimension to the palate and aromas of a wine.
2. Importantly, I find that adding a percentage of whole cluster adds aromatic freshness to older Pinot Noirs. A Pinot Noir that is ten years old and has a percentage of whole cluster will be more aromatically complex than the same wine 100% de-stemmed.
3. Region and vintage are the deciding factors. There are some regions where stems do seem to retain an aggressive green character and therefore it is difficult to do much whole cluster. By the same token, there are regions which seem to benefit dramatically from a percentage of whole cluster as the added complexity really changes the wine. An example is Central Otago, where some of my favorite producers do whole cluster and where we are doing quite a bit at Burn Cottage Vineyard, my client there. The Central Otago fruit seems to really benefit from whole cluster.
4. Stem ripeness varies dramatically from vintage to vintage and this is an important consideration. Ripeness is in the eye of the beholder. I will never forget a tasting with Henri Jayer in his cellar in around 1984 when he stated emphatically that there are never ripe stems in Burgundy.
5. Over the years I have been personally more committed to making wine with no additives except SO2. For example, at Littorai we use no cultured yeast, yeast nutrients, cultured MI bacteria, bacteria nutrients, enzymes and, importantly, no acid additions. Therefore, I am very careful that we do not add so much whole cluster that it would require us to acidify. The final decision on the percentage of whole cluster becomes reflective not only of region and vintage, but also of the desire to stay true to the path of “natural” winemaking.”

David Lloyd, Winemaker, Eldridge Estate, Mornington Peninsula, Victoria, Australia “I recently attended a tasting of winemakers’ experiments. Some of the experiments looked at tannins and whole cluster. The summary of the discussion was as follows. De-stemming and adding back the stems in layers gives coarse tannins because of cell damage occurring during the de-stemming process. Whole cluster requires earlier pressing to make sure sappy tannins are not extracted. One experiment involved foot stomping. One batch was divided into 3. Batch 1 was whole berry de-stem only with 14 day pressing. Batch 2 had 1 hour of foot stomping about a week after de-stemming to make a soup and was pressed after 14 days. Batch 3 was similar to batch 2 except pressing occurred after 21 days. Everyone preferred Batch 1 indicating tannin extraction encouraged by foot stomping is quite different to what happens without it.”

“The problem with whole bunches is that it varies from season to season. In a year where the stems are ripe, the wine can gain body and an element of tannin that goes well with secondary fruit flavors ten years down the track. The green edge is very hard to predict. I have seen yanks and yocals carry on how they have a test or that they can chew the stems to determine ripeness, but my observations are that years of experience helps but it is still hard to get right.”

“The off feature is a green, herbal element that goes from an edge to a dominating feature. Some areas can risk it more often than others but my feeling is that you don’t want to fight terroir. Generally, my Pinot Noir is about pretty fruit flavors and elegance. Stems will either give me a green edge to that, or too much tannin or a very herbal feature, so after five years of experiments, I gave up.”

“Many places in Sonoma, for instance are fine, but if they choose to pick less ripe I wonder whether they too will have greenness as a feature rather than an edge. Burgundians have largely moved to 100% whole berry and sometimes add back stems or add a percentage of stems at a selected point in the ferment. Someone has done work on the green feature versus the time stems are added, and I have a vague memory that a green edge develops if whole bunch is present during cold soak and does not develop if stems are added back when the ferment is under way.”

Jesse Lange, Winemaker, Lange Estate Winery (Oregon) “Ahh, whole cluster fermentation. We don’t employ that technique here at Lange Estate for the most part. I do, however, try to have a percentage (75%) of whole berry going into the fermenters. Most of those berries will be broke in the first few days, to avoid a heavy percentage of carbonic maceration, but I like the varying rates of “mini-fermentations” within the must. Most of the whole cluster trials we have done here indicate that, on the whole (pun intended), it doesn’t fit our style, especially when it comes to texture. Stem ripeness is the largest factor for whole cluster and trying to locate that moving target can be tricky for sure. The wood tannins can certainly add some structural backbone, but they can also influence texture and mouth feel in a negative manner. When I worked at Santa Barbara Winery in 1996 and 1997, I liked whole cluster ferments for some of our lots of Pinot Noir and Syrah, and not so much for others. The stems in Santa Barbara County seemed to be far more advanced in lignification than those here in the Willamette Valley.”

Laura Volkman, Laura Volkman Wines (Oregon) "While I don't have experience with whole cluster fermentation, I do have a few comments. My theory is that the stems/rachi need to be mature and brown at harvest to add desirable wood stem tannin and aromas to the wine. In a cool year, the stems could add those undesirable bitter harsh green tannins and make the wine herbaceous. In an optimal year, I have worked with winemakers who add 10% or so whole clusters to the fermenter and the wines ultimately show more tannin, toast and nice astringency than if the stems were not added. These winemakers ran the rest of the grapes through the crusher.

In carbonic maceration whole cluster fermentation, the grapes are not run through the crusher to avoid twisting and scraping of the stems during processing and maintain whole berries. They are added directly to the fermenter and the extraction is done in a carbon dioxide saturated environment. The theory is that whole cluster is more gentle on the fruit overall, more of the berries are left intact along with the stems/rachis, and any extraction from the wood stems is softer allowing more of the fruit to show through.

While I think whole cluster wines are lovely and I enjoy them on occasion, my style is more traditional with gentle punch downs that extract tannins from the skins and seeds. I can control and balance this with fermentation temperatures and more or less aggressive punch downs. I think tannin extraction is very personal to the winemaker's palate, especially post fermentation. We need to get our head and hands in the fermenter during this time to know when to press off.

Wes Hagen, Winemaker, Clos Pepe Estate Vineyard and Estate Wines “Whole cluster fermentation is a Burgundian affectation that I have experimented with. While I agree that it adds some tannin and mid palate mouth feel to young wines, the broccoli stem/veggie/soy sauce character it seems to add to a young wine is not a flavor I enjoy in Pinot Noir. I spend considerable time with canopy management to get the veggie out of Clos Pepe fruit and not sure why I would want to put the flavor back in via stem inclusion. When asked why I don’t use stems in Clos Pepe wines, I usually give two answers: #1 I grow grapes to make wine, not stems, and #2 If you need better mouth feel out of Pinot Noir, structuring the wine with a little more acidity seems to be a better solution than letting the grapes get too ripe and flabby and then using stems to put a bit of bones back onto the flesh.”

“Stem inclusion does seem to integrate in a bottle-aged Pinot Noir, say 4 to 5 years down the line, just like oak, but at that point the tannins are mostly polymerized anyway, and the contribution to mouth feel is likely minimal. I believe taking Burgundian production techniques and applying them to California Pinot Noir is antithetical to developing our own regional identity - like bringing Hinduism to Salt Lake City. You may start with a few adherents, but eventually you will be talking to yourself.”

Roger Boulton, Stephen Sinclair Scott Professor of Enology and Chemical Engineering, University of California at Davis “The contributions of whole cluster fermentation are at least due to two aspects: the intact berry aspect of the whole cluster, and the extraction and adsorption properties of the stems. The first would be similar to that of whole berry effects, which make small contributions normally seen in carbonic maceration. The berry cells undergo a biochemical modification internally, partly fermentation like, but with significant modification of monomeric phenols that results in the carbonic maceration aroma character. This is generally released and most obvious at pressing when it is mostly released into the surrounding wine. The second aspect is thought to be minor, even insignificant from a sensory point of view. While stems can have higher tannin concentrations than berries, there is little evidence that it is actually extracted under winemaking conditions. In fermentations with dry, woody stems, there can be a herbaceous aroma contributed, even a black tea or cedar character. The trials of stem additions that resulted in the tea and cedar character were when stems which had been removed from the berries were added back and not whole cluster fermentations as such. Similarly, there might be some components that would be adsorbed to the stem tissue, but I know of no data that establishes this, either positive or negative.”

“There are some questions whether these practices developed from reliable sensory trials, or rather came about by people going back to minimal handling at the point of cluster to juice, and how much whole clusters and intact berries survive the first days of punch downs, treading, or pump overs. I do not know of any well controlled trials that have shown significant and reproducible effects, despite considerable anecdotal opinion.”

“There are questions regarding Pinot Noir flavor and aromas versus treatment and other contributions due to style. There will always be the question of expression of terroir and whether stylistic practices mask it or not.”