Whole Cluster Fermentation

Whole cluster fermentation, also called whole bunch fermentation, places intact bunches of grapes in the fermenter rather than grapes that have been destemmed and/or crushed. The more popular alternative is to remove the berries from the clusters and discard the stems before crushing and fermentation. It is not all or nothing: a winemaker might add a few whole clusters to destemmed grapes or go to 100 percent whole clusters. The method is old. Before the crusher-destemmer was invented in the nineteenth century, almost all red wines would have been fermented as whole bunches.

• Placement: intact bunches most often go on the bottom of the fermenter with destemmed and/or crushed berries on top; some winemakers put them on top instead, and extraction from the stems is greater when bunches are fully submerged
• Protection: even in '100%' whole bunch ferments, many winemakers make sure there is some liberated juice in the bottom of the fermenter, and the CO2 from its fermentation helps protect the rest of the fruit from oxidation
• Pressing: stems act as drainage channels through the skins and seeds, so musts with whole bunches generally press very easily and quickly
• Not for every grape: it is not common with Cabernet Sauvignon and related varieties, because the high methoxypyrazine concentration in their stems can give 'cut grass' and 'herbal' characters

Stem ripeness shapes the result. As stems ripen they become lignified, which lessens the herbal and vegetal notes contributed by methoxypyrazine compounds. Lignification is the hardening of the stem, and lignified stems can remain bright green. The best results come from bunches with highly lignified, woody stems. The best-lignified stems are likely to be found in low-vigour parts of the vineyard, because lignification starts when shoot growth stops; it tends to be lower in wet years, in high-vigour vineyards, in cool climates and in cooler years. Stems also change the wine's chemistry. They contain potassium, which combines with tartaric acid and precipitates, so titratable acidity is lower and pH is higher. In Côte d'Or wines made with and without whole clusters, whole clusters lowered alcohol by as much as 0.5 percent and acidity by as much as 0.4 g/l (as sulfuric), and raised pH by as much as 0.13.

• Green aromas: stems in Shiraz and Pinot Noir ferments can significantly increase the concentration of IBMP, and in Pinot Noir 'capsicum' aroma was strongly related to the proportion of whole bunches
• Tannin: sources differ. Tannins have been found to rise in proportion to the percentage of whole clusters and stems, but Andrew Jefford argues in Decanter that most of the tannin comes from skins, not stems
• Colour: stems absorb colour and lower anthocyanins, yet in a 2018 AWRI trial with Adelaide Hills fruit, whole bunches raised perceived colour intensity in Shiraz and red colour intensity in Pinot Noir

Carbonic maceration is a whole bunch fermentation technique in which the first phase of fermentation takes place in a completely anaerobic atmosphere, without the intervention of yeasts. It happens only if the grapes stay intact with no free juice, in a closed vessel filled with carbon dioxide. Semi-carbonic maceration, or adding a share of whole bunches to crushed grapes, gives some carbonic maceration inside the whole berries but less of its distinctive flavour. Carbonic and semi-carbonic maceration are commonly applied to Gamay, Pinot Noir and Shiraz, for light-bodied, brightly coloured, perfumed or fruity wines intended for early consumption. In Beaujolais, Gamay noir à jus blanc is picked by hand and put into vats in entire bunches, still on the stalk. At the top of the vat, the bunches sit in an atmosphere where carbonic gas replaces the oxygen, and fermentation begins inside the berries. At the bottom, the compressed grapes release juice that yeasts ferment into alcohol. In Beaujolais this whole process is called semi-carbonic maceration; the vat is not hermetically sealed and no carbonic gas is added.

• Maceration time in Beaujolais: around 10 to 15 days for the ten crus, 6 to 10 days for Beaujolais and Beaujolais Villages, and 4 to 6 days for Beaujolais Nouveau
• Stems as drains: Mathieu Lapierre of Marcel Lapierre in Beaujolais says that with carbonic maceration they never want to extract what is in the stems and need them only as drains in the vat

With every new vintage in Burgundy more producers adopt stems, and in many other regions the technique is both a tool of the avant-garde and a staple of arch-traditionalists, Andrew Jefford wrote in Decanter. Winemakers interviewed by GuildSomm named good examples in Merlot, Nebbiolo, Gamay, Trousseau, Poulsard, Syrah, Grenache and Mourvèdre.

• Pinot Noir, Burgundy: in a survey of Côte d'Or producers for a 2014 Master of Wine dissertation, slightly under half of 245 respondents reported using whole clusters; Domaine Dujac uses whole clusters in high percentage, averaging 85%, almost every year
• Pinot Noir, Oregon: a large number of Willamette Valley wineries now routinely include some whole cluster in their Pinot Noir; at Cristom, Steve Doerner settled on roughly 50% most of the time after arriving in 1992
• Pinot Noir, California and beyond: at Calera, all Pinots were 100% whole cluster by the time Doerner left; Jefford's tasting included 100% whole bunch Pinot Noir from Alsace (Léon Beyer) and the Yarra Valley (Timo Mayer)
• Syrah, northern Rhône: Stéphane Ogier's Côte-Rôtie La Belle Hélène is always made with 50 percent of its stems, and Ogier says he likes stems more and more, but only from the Côte Brune; in the Côte Blonde they can be too aggressive
• Syrah and Gamay, California and Australia: in Sonoma, Pax Mahle includes more whole cluster for Syrah and ferments Gamay 100% whole berry/whole cluster for most of the fermentation; Taras Ochota of Ochota Barrels in South Australia uses whole bunches for nearly every red, from about 50% to 100%
• Grenache, Sierra de Gredos: Daniel Gomez Jimenez-Landi's Las Uvas de la Ira from Méntrida is made with 100 percent whole bunch and no working of the marc
• Nebbiolo, Barolo: Marco Parusso lets the grapes for his Barolos rest until the stems turn brown, then ferments whole bunches, a technique Wine Spectator calls rare in Barolo

Whole-cluster pressing is a pressing method, not a fermentation one. In Champagne, the legislation stipulates that the clusters must reach the pressing centre whole, and to date the only way to pick whole, undamaged clusters is by hand. A white Champagne can be made from black grapes by slowly pressing whole clusters, so the juice flows quickly through the press cake before the skin pigments can colour it. The pressed juice is then settled, and the clear juice is sent on to fermentation.

The biggest risk is extracting 'grassy' and 'herbal' aromas and flavours and overly astringent tannins from the stems. A cautious start is advisable: a small percentage of whole bunches at first (10 to 15 percent), or a small batch that can be blended into other wine until the desired effect is reached.

• Higher pH: stems add potassium to the must, which can change the buffering capacity of the juice and raise the pH of the finished wine
• Volatile acidity: in a two-vintage study of Edna Valley Pinot Noir, volatile acidity and higher pH were identified at 100% whole-cluster inclusion
• At the press: a sudden change from positive to negative characters can occur, so it is important to taste continually from the press tray; intact berries can also release a substantial amount of sugar, so the wine should not cool dramatically, to avoid a stuck fermentation
• Logistics: stems often 'bridge' in press hoppers, so slow tipping and long-handled tools such as pitchforks help
• Carbonic spoilage: during carbonic maceration, the risk of acetic acid bacteria and Brettanomyces rises because of higher pH, high temperatures and the absence of sulfur dioxide

Use these as cues, not proof. When stems are lignified, the flavours they add tend toward black tea, floral or forest floor notes; underripe, green stems bring green, vegetal and herbal notes, and in Shiraz, 'stalky' and 'capsicum' character rises with the share of whole bunches. On the palate, look for texture and freshness: to trained sensory panels, wines fermented with whole clusters taste fresher despite their higher pH. Carbonic character is different again, often 'fruity' with strawberry, raspberry and cherry aromas, particularly in Beaujolais. Differences can be subtle: in a Côte d'Or blind tasting of paired wines, the differences tasters identified between destemmed and whole-cluster wines were subtle.

Sources: https://www.awri.com.au/industry_support/winemaking_resources/winemaking-practices/winemaking-treatment-whole-bunch-fermentation/, https://www.awri.com.au/wp-content/uploads/2020/06/s2162.pdf, https://www.awri.com.au/industry_support/winemaking_resources/winemaking-practices/winemaking-treatment-carbonic-maceration/, https://www.beaujolais.com/en/2020/09/22/beaujolais-vinification-a-process-like-no-other/, https://www.champagne.fr/en/champagne-frequently-asked-questions?nid=608, https://www.champagne.fr/en/about-champagne/how-champagne-is-made/settling. Last verified 2026-10-17