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This article originally appeared in the May 2017 edition of Grapegrower & Winemaker.


While the mention of whole bunch fermentation appears on plenty of back labels from emerging and artisan wine brands, there are lots of reasons this method is more than just a marketing tool. When executed correctly it ads complexity, structure and soft tannin. Camellia Aebischer reports.

Prior to modern machinery, most of the world drank wine that was fermented in whole bunches. It’s only in the past 160 years or so that the process of de-stemming was adopted. After the practice of stripping grapes from stems was hailed as producing a purer form of wine, the technique took off and whole bunch was almost laid to rest.

Recently there has been a resurgence in winemakers carefully exploring whole bunch fermentation. The results can be more complex and savoury, and are even claimed to bring structure to fruit from young vines. But with everything, there’s a right and a wrong way. As Timo Mayer (of his namesake label) puts it, “If it tastes like stalks, you fucked up.”

“If it tastes like stalks, you fucked up.”


A lack of care can turn a complex batch in to an astringent green mess, so picking should be done late, when the stalks are older and the grapes are sweetest. Mayer recommends avoiding the process for cool climates, as the extra tannic skins don’t balance well with the addition of stalks.

However, cool climate shouldn’t be ruled out. Peter McGlashan, of Ridgemill Estate, has had success enhancing his Shiraz through the addition of whole bunches.

Some winemakers choose to select the grape varieties according to their flavour profiles, since doubling up on herbaceous-ness can become overpowering. Merlot, Cabernet Franc and Cabernet Sauvignon usually don’t meld well with whole bunch if care isn’t taken, but Mayer is challenging that by producing a whole bunch Cab Sauv, along with his Pinot Noir, Gamay, Nebbiolo and a Shiraz.

In Burgundy, Pinot Noir is made using whole bunch ferments, as well as a number of wines under a variation of the label ‘Nouveau’. The stalks absorb pigment and add a little extra water, which gives the wines their lighter colour and slightly lower alcohol content.

When grapes are left on the stems, the berries are often kept fully intact, which allows fermentation to begin on the inside. This is known as ultra-cellular fermentation, and is brought on by the enzymes in the berries, instead of yeast.

The technique can also be used on white grapes that spend time on skins

First, the berry consumes its stored carbon dioxide (CO2), then moves on to its sugars, which it converts and, in turn, produces more CO2 to sustain the process. If there is exposure from the air for added CO2, the berry will consume it. The benefit of leaving bunches whole during this initial fermentation is that the stalks make space between the grapes, providing airflow perfect for absorbing CO2.

After one to two weeks, the level of alcohol from enzyme fermentation reaches its tipping point and the enzymes die off. During or after this process, winemakers often choose to crush a portion of the berries to encourage a typical fermentation alongside, whether it be a puddle in the bottom of the tub or submerging the berries in fermenting juice. The latter produces more tannins as the juice has more direct contact with stems.

When the enzyme fermentation process is solely undertaken, without crushing the berries or adding yeast, it’s known as carbonic maceration. For this process, grapes are usually sealed in bins and CO2 is pumped in for maximum exposure. This produces a soft, fruity wine with low tannins.

“I can regulate the tannin with the number of berries crushed. A lot of people fine wines to make them drinkable but we don’t, so we just crush the berries to regulate the tannin content.”


Although this technique is seldom used in Australia, winemakers like Mayer adopt some of its practices by leaving fruit undisturbed to do its business. “I ferment them in the picking bins, I sort the fruit in the vineyard and then that’s it.

“I do start crunching a little corner of the bin if I need, because we don’t add yeast and I’ll stomp accordingly,” says Mayer. His secret for getting the ferment going is to throw in a bucket of grape must that’s already begun fermenting, as a sort of ‘starter’.

“I can regulate the tannin with the number of berries crushed. A lot of people fine wines to make them drinkable but we don’t, so we just crush the berries to regulate the tannin content.”

Winemaker and owner of Spinifex Wines in the Barossa Valley, Peter Schell, has a different technique for regulating his wines. When the grapes come in, he divides them up and will ferment each portion differently, blending to achieve the right end result. Some are processed as whole bunch fully carbonic, some crushed and a majority crushed with some bunches added.

“I don’t have wines that are bottled as 100% whole bunch but there would be some that are, it’s just not on the label,” says Schell. He’s considerate that each year the conditions always vary, meaning that stems can be greener at harvest some years, and riper in others, so his technique changes to suit the season.

“You just sort of make it up on the spot. Shiraz would be 25-35% whole bunch and Grenache more, because it’s a lighter more aromatic style, but it depends on the crops. Grenache can have very thick green stems,” says Schell.

Peter McGlashan said that “the most important part about whole bunch is making sure that the stalks are ripe and have started to lignify (become woody), because if they’re under-ripe you’re going to get a lot of green tannin which will make the wine aggressive.”

McGlashan’s process differs from Schell in that he ferments his whole bunches in the same container as the grape must, allowing the carbonic maceration to take place alongside a typical ferment. His ratio is 20% whole bunch, which is all processed together.

“I started off slowly, using small vats of whole bunch and worked up to twenty percent. I’ve done a few projects with Gamay using 100% whole bunch which is how I improved my technique for the Shiraz.

“The colour isn’t as intense, but it has a different dimension, I call it a cuddliness.”


“The colour isn’t as intense, but it has a different dimension, I call it a cuddliness.”

Although these three methods all differ, they can agree on one thing, and it’s that there’s technique in processing the stem correctly. If this is done right, the result is silky tannins and an added complexity. “Whole bunch is a lot more savoury, you get different tannins and it’s more structural,” says Mayer.

Depending on the region, stems and grapes will ripen at different rates. Not all areas have the luxury of picking whenever they want due to climate and rain, but regardless of when the grape is picked, it’s easy to tell when the stem is ripe.

“They’re a bit woodier and the colour isn’t as vibrant, not green like grass anymore, much duller,” explains McGlashan.

“If the peduncle, which joins the cane to the bunch, is brown, 90% of the time you know that the stalk is going to be ripe. As that peduncle lignifies there’s a little elbow join, and as it ripens at a certain point that closes off [stopping supply of nutrients to the bunch].

“When the fruit is at the correct point and the peduncle is brown, you can easily just pick the bunch with your hands. If it’s the right level it can be quicker than picking with snips.”