A RED wine that suits all occasions at the dinner table must be smooth, velvety and supple on the palate. Not too heavy, not too alcoholic, not too jammy but pleasantly fruity and not overpowering. It should be an all-rounder, preferably medium bodied. So, what fits the bill? Well, I’d recommend a gamay or another grape that has undergone some sort of carbonic maceration.
This technique, applied at the start of the winemaking process, was once pigeonholed to only Beaujolais in France, but now it is a primary colour in a winemakers ‘palette’. In one version or another, carbonic maceration can be found in the production of Australian shiraz, grenache, pinot noir and a swathe of other red wines.
Carbonic maceration or maceration carbonique is a complex intracellular fermentation of whole grapes which is carried out in an anaerobic environment with no juice contact. The fermentation is not a normal one as yeast is not involved. According to an article published in the Australian & New Zealand Grapegrower and Winemaker in 2018 and written by the AWRI it involves an enzyme called malic dehydrogenase which metabolises the grapes malic acid into ethanol, succinic acid and aminobutyric acid. Glycerol and shikimic acid is also produced which leads to a number of aroma compounds such as benzaldehyde (kirsch) and ethyl cinnamate (cinnamon or strawberry). The whole reaction takes about a week. When gamay gets the full treatment, you end up with strawberry, cherry, kirsch, confectionary or bubble-gum aromas which can be a bit overwhelming. So partial carbonic maceration is far more popular.
To enable this inner berry fermentation, you must start with hand picking the grapes so as not to damage them. They must also be healthy with no sign of damage or rot. Once the grapes are received in the winery the decision-making starts. Winemakers can choose from full or partial (semi) carbonic maceration. Similar to carbonic maceration, winemakers often choose to experiment with partial, whole bunch or destemmed whole berries.
Full carbonic maceration involves placing whole bunches into a stainless steel vat and covering them with CO2 to exclude oxygen. Together with a temperature of around 30 degrees, this creates the right conditions for some of the sugars to turn into alcohol. Once around 2% of alcohol has been created the berries will swell and split. When used with gamay grapes to produce a simple Beaujolais Nouveau, the fermentation is quickly carried out without skins once the desired colour is achieved. The resulting wine is fresh and fruity with low tannins and meant for immediate consumption. Alternatively, the wines are fermented on skins as normal, which will produce a more complex and heavier wine.
Semi-carbonic maceration is more popular and doesn’t involve adding carbon dioxide. Here whole bunches are placed in a vat and the bottom layer is crushed by the weight of the grapes on top which releases some juice that starts to naturally ferment. This naturally produced CO2 triggers an intra-cellular fermentation within the unbroken berries. Once the 2% alcohol barrier is reached the skins again break and a normal on skins fermentation can take place in the vat.
Another slight variation is adding a proportion of whole bunches into a normal fermentation. The submerging of these bunches will create the anaerobic conditions to create a carbonic maceration. Hand plunging will eventually break these bunches up. If whole bunches are used, then the stems must be fully ripe. Using stems can increase tannins and add a spicy character to the wine. This can add complexity and weight to a pinot noir for example. Should the stalks be under-ripe or not required due to the tannic nature of the grape variety, then whole berries can be added to the fermentation as another alternative. There are a number of wines that use both, and in the same vat, creating a layered cake of different ferments going on!
In the Adelaide Hills Winemaking Director Kym Milne MW at Bird in Hand uses a combination of these different techniques. “Our syrah is usually around 20-30% whole bunch, maybe 10-20% whole berry and the rest more traditional ferment – although these percentages will vary from year to year.” Kym explains. “The whole bunch gives a definite aromatic lift to the wine – the slightly stalky/pyrazine notes give the wine some lifted florals, ‘pretty’ potpourri-like aromatics and a general vibrancy both on nose and palate. The whole berry component we use is after it has been selectively harvested by machine, which gives us predominantly whole berry’s in the bin. We then tip these straight into the fermenter rather than crushing the berries. Whilst not a full Carbonic Maceration in the traditional sense, we find the resultant wine definitely has a slight ‘Cab Mac’ note, with bright berry fruit but without the pyrazine notes of whole bunch. Also, the wine tends to have softer tannins due to the lower extraction of the whole berries vs crushed berries in a traditional ferment “
The approach to whole bunch, whole berry fermentations varies across regions and wine styles. Sutton Grange in the Bendigo region, for example, can use on average up to 35% whole bunch in making their Estate Syrah, but depends on the vintage. Winemaker Melanie Chester varies her approach for each batch. “Some ferments we use whole bunches on top of the ferment, whilst in others we place them at the bottom. The top results in more aromatics, a certain savouriness and layered tannins. Whilst bottom bunch ferments give us more juicy, fleshy wines,” she observes.
In neighbouring Macedon Ranges winemaker Matt Harrop estimates he uses 15-20% whole bunch in Curly Flat Estate Pinot Noir. “This year (2021) we made 19 different fermentations from the various sites within the vineyard and each tank was slightly different. I like the aromatic lift it gives the wines and also spice in some ferments,” Matt adds. Whole berries are also used extensively. “We don’t have a crusher here so there is a lot of whole berries as well. It provides a gentler tannin extract,” he adds. In discussions with Matt, it seems the fruit from older vines or cooler sites can receive more whole bunch and also more oak treatment, as long as you treat them gently to avoid any stem greenness.