In a previous post, we elucidated and compared the use of whole bunches compared to crushing and destemming the bunches before fermentation. This month, we are delving into the fermentation process and focusing on the whole bunch method, and how it is used here in the Oldenburg Vineyards cellar.
Whole bunch fermentation is typically used on varieties like Syrah, as well as Pinot Noir and even on Grenache Noir. It is not suitable to use on Bordeaux varieties, as the harshness of the stems and pips will cause an overextraction of the “green” characteristics. Whole bunch fermentation can be 100% (which Nic used on some Syrah in the 2019 vintage). In this case, the bunches are put into the tank completely whole (skins, stems and all), trodden down to extract some juice and left to complete semi-carbonic maceration. Carbonic maceration is a winemaking technique used widely in regions like Beaujolais, where whole grapes are fermented in a carbon dioxide rich environment before crushing. At Oldenburg, an element of carbonic maceration happens during whole bunch fermentation.
The extent to which we use whole bunch fermentation (100% or a smaller percentage – down to as little as 10%) is dependent on the lignification of the stems (how much they have browned and hardened). If a vineyard is extremely vigorous and the stems are very green, Nic will not use whole bunch fermentation, as an overextraction of greenness will occur, which can give a very green, grassy and bitter character to the wine. In the end, it’s all about balance and determining what works for the specific vineyard.
During whole bunch fermentation, the carbon dioxide produced protects the bunches, and an intra-cellular fermentation takes place inside the whole berry. This leads to a decrease in colour extraction (remember, colour is extracted from skin contact, which is increased when berries are crushed and destemmed, as the juice is exposed to the skins more) as well as a decrease in alcohol – by about half a percent.
One potential drawback (that can be managed) is that whole bunch fermentation causes a decrease in acidity, due to a release of potassium from the stems, which binds acid and causes it to settle out. This is a small price to pay in exchange for all the advantages, including beautiful fine powdery tannins, a beautiful light colour and a gentle spiciness and freshness added to the wine.