Winemakers are increasingly looking to oft-forgotten techniques to improve the quality and elegance of their wine, enhance specific styles and facilitate processing in the cellar.

Whole-bunch pressing, whole-bunch fermentation and carbonic maceration all have one thing in common – the presence of whole berries or bunches during pre-fermentation pressing in the case of white wine, fermentation, usually for red wine production, and post-fermentation pressing for red wine production, although it could be argued the red berries are no longer whole or intact at this stage. But why devote an entire article to these techniques when some of them are sometimes described as old-fashioned or rustic?

This article focuses on the experiences of four winemakers who employ these techniques in their quest to make the best possible wines. As with any winemaking technique, there are pros and cons and ultimately the winemaker has to make the call whether the advantages outweigh the drawbacks.

Whole-bunch pressing

Whole-bunch pressing offers a range of benefits compared with the traditional method, which usually involves destemming and crushing white grapes. Traditional crushing and destemming may be quick and easy, but by not crushing individual berries, as is the case with whole-bunch pressing, the must has lower concentrations of phenolic compounds and the resulting wine is more delicate and elegant. Additionally, some regard whole-bunch pressing as essential for the production of high-quality sparkling white wine.

Whole-bunch fermentation

Whole-bunch fermentation might cause a fair amount of confusion, as this technique probably overlaps with carbonic maceration. For the purpose of this article carbonic maceration and whole-bunch fermentation are described as separate techniques as the winemakers we interviewed described their techniques as such and they are indeed quite different.

For instance, whole-bunch fermentation could involve a small vessel such as an open-top fermenter or a bin containing a mix of whole bunches, whole berries and crushed berries. Some degree of carbonic maceration may take place but it’s not a requirement. The winemaker may also do manual punch-downs which damages some of the remaining whole berries during maceration and fermentation. Inoculated yeast and malolactic bacteria may also be present from the beginning of maceration. Although the lines are blurred, winemakers can employ this technique to their advantage.

Carbonic maceration

Carbonic maceration has many guises, but strictly speaking the classical version invented by Michel Flanzy in 1934 is the real McCoy. As the method is complex, it won’t be discussed in full. For details go to http://ow.ly/3fOX30cuJ3P.

The most important action during carbonic maceration is the occurrence of anaerobic metabolism in the grape cell. Under anaerobic conditions, intact berries shift from oxidative to fermentative metabolism. Anaerobic metabolism is characterised by intracellular fermentation (no yeast is present at this stage) during which small amounts of ethanol (1.5-2%), glycerol, acetaldyhyde and organic acids are produced. Malic acid is an important molecule during anaerobic metabolism as it is catabolised to ethanol and succinic acid in the absence of malolactic bacteria. Classical carbonic maceration can be tricky to achieve since it requires very specific conditions such as intact and healthy berries preferably still in bunches. These bunches must be placed, with minimal damage, in a sealable vessel which can be flushed with carbon dioxide. Good temperature control of the vessel is also paramount.

Wines made by carbonic maceration are characterised by aromatic complexity, softness and balance. Fixed acidity and residual sugar contents are also generally lower in these wines than in conventionally produced wines.

We next explore whole-bunch pressing, whole-bunch fermentation and carbonic maceration from four winemakers’ perspectives. Izele van Blerk of KWV, Craig Hawkins of Testalonga Wines, Adi Badenhorst of AA Badenhorst Family Wines and André van Rensburg of Vergelegen Wine Estate give their insights into the various techniques.

Izele van Blerk

“I prefer doing whole-bunch fermentation on Shiraz, Grenache Noir and Cinsaut,” Izele says. “There are two ways of doing it – whole bunches or whole berries. When I work with Shiraz and Grenache Noir, 25-30% of the tank is filled with whole bunches and the rest of the tank with crushed grapes.”

It’s very important that the stems are ripe or the wine can have a green taste. There are several advantages to incorporating whole bunches. “I experience fruit lift and the tannin is finer and chalkier, almost like a cool climate Chardonnay. I’ve also noticed cool climate Shiraz expresses more spiciness. With Grenache Noir there’s more fruit, red berries and the tannins are finer. When I work with this cultivar the bunches must be ripe and the berries slightly bruised as this improves pump-overs.”

Izele also does whole-berry fermentation on Petit Verdot, but this is the only Bordeaux cultivar that gets this special treatment. She says it helps the expression of fruit, particularly floral and red berry aromas.

Izele, who doesn’t shy away from experimentation in the cellar, did whole-bunch fermentation on Pinotage for the first time this year. Tank one (the control tank) was 100% crushed and inoculated with a commercial yeast strain, with pump-overs every three hours. Tank two was done in the Pinot Noir style and was 100% crushed and inoculated with a commercial yeast strain, but pump-overs were done only every six hours. Tank three contained 30% whole bunches, with no yeast inoculation and three-hourly pump-overs.

“Wine one showed the traditional style, with ripe fruit, plums, good structure and plenty of concentration,” Izele says. “Wine two had a finer tannin structure, more red fruit and was very elegant. Wine three showed a combination of dark and red fruit and finer, more integrated tannin and spices. The fruit was much more expressive. Interestingly, the volatile acidity of wine three was lower than that of the other two wines. I won’t bottle this wine on its own, but it’s excellent for fruit and complexity contribution as 10-15% of a blend.”

Craig Hawkins

“I’ve been making my own label for 10 years and played around with many techniques and developed my own style,” Craig says. “Carbonic maceration, or at least my version of it, is not strictly speaking carbonic maceration. Traditional carbonic maceration was developed in the ’60s and ’70s in Beaujolais by producers such as Jules Chauvet who used it as a technique to counter high acid, including malic acid. The resultant wines were softer, fruitier and more enjoyable than previous styles from the region.
I suppose it was the defining moment of Beaujolais as when we think of that region, we think of carbonic maceration – or at least I do.

“I’ve taken what works best for me from carbonic maceration to create wines I like to drink. In the strict sense carbonic maceration produces similar flavours that are produced because of specific enzymes that release a certain flavour profile. I want my wines to taste like my wines and my region, not like carbonic maceration wines.

“What I like about carbonic maceration is that in our warm climate – and this is an important element – it can release a lot of tannin, which I enjoy at certain levels. It’s the control of this tannin that underlies all the key decisions I make. All my red grapes are processed in the same way – I don’t destem, but the difference comes with when I press and how much I crush. These are my most important decisions and I make them based on feeling and tasting – I never analyse pre-fermentation or at picking.”

Adi Badenhorst

For Adi, whole-bunch pressing in his cellar has practical and qualitative purposes. “If I have to compare white wine where the grapes were destemmed and crushed with white wine where the grapes were whole-bunch pressed, the first thing to note is that the whole-bunch pressed wine has lower pH,” he says. “The must is also cleaner and there is less lees. Finally the must is lower in phenols. We don’t have enough space to accommodate settling, so there’s also a practical consideration when it comes to whole-bunch pressing. We go directly from the press to the barrel or tank for initiation of fermentation.”

Adi also uses whole-bunch fermentation for red cultivars. “Our red grapes are 90% whole-bunch fermented as we don’t have a crusher and destemmer. The whole bunches are crushed by means of our klappomp after which they’re pumped directly into the fermentation tanks. I experience more tannins with these wines compared with wines where the grapes are crushed, destemmed and pressed, processes which make them fresher. These tannins contribute to a longer finish and are more stable. I also use no new wood on these wines.”

André van Rensburg

For André whole-bunch pressing of grapes for Chardonnay, Semillon and sparkling wines (Chardonnay and Pinot Noir) is part of the quality philosophy at Vergelegen. “Whole-bunch pressing allows much less mechanical interaction with your grapes, which in turn results in must with lower turbidity, pH and less lees,” he says. “At the same time acid is retained and delicacy is enhanced. Base wine for sparkling wine production gets no sulphur dioxide and the must is treated oxidatively, while must for Chardonnay still wine production gets 20-30% less sulphur dioxide than wine prepared the traditional way by crushing and destemming.”

Semillon, which is planted on a south-facing slope and often bears the full brunt of the wind, also gets the whole-bunch treatment. “The plant has to adapt to the battering effect of the wind, which causes the berries to have a higher phenol content,” André says. “Destemming and crushing are definitely not options in this case. I press the whole bunches and the whole process is oxidative to reduce the effect of phenols. After pressing the must goes to the fermentation tanks and there is no or very little sulphur involved.”

There is another important consideration that makes whole-bunch pressing an extremely valuable tool, André says. “Whole-bunch pressing is the method par excellence when there’s potential smoke taint. Because there’s less mechanical interaction, it follows that less of the smoke taint compounds are released into the must.”

But whole-bunch pressing is not all sunshine and roses, he cautions. “This method has its disadvantages. Everything must be hand-harvested and brought into the cellar in crates. This method is labour-intensive, lengthy and thus expensive. Getting Semillon into your press takes up to a third longer than the traditional method. Your juice yield is also lower and we don’t do natural fermentation on whole-bunch pressed juice as there is too little yeast carry-over from the press to the fermenter.”

The techniques and their various adaptations and uses outlined here once again show the ingenuity and experience of our winemakers, but they’re clearly not for everybody or every situation. The judicious application of these and all the other winemaking techniques is a daunting task, but ultimately leads to success.

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