Continuing with the harvest theme, this month we are looking at the different methods of pressing the grapes (the process to get the juice out of the berries). It might seem straightforward (squeeze the berry and the juice comes out, right?) but there are actually two very different methods of pressing that can be used to retrieve that precious juice. So let’s look at how they work, and why (especially for our white grapes), Nic uses the one method and not the other.
The two methods we’ll be investigating are whole bunch pressing (which we use on our Chenin Blanc and Chardonnay) and crushing and destemming. The names are fairly descriptive in this case – the former process entails putting whole grape bunches into the press, while the latter adds the step of destemming (removing the stems) and crushing the grape berries before loading it into the press.
We’ll start with the method that we prefer when making our Chenin Blanc and Chardonnay: whole bunch pressing. This method is generally used extensively for the making of Champagne or MCC. It is a more delicate process, which presses the grapes more gently, producing a more elegant, cleaner juice. It also produces less lees (2-3% of the total volume, compared to about 20% when using crush & destem) and less phenolics in the grape juice. The juice also has a lower pH and better acidity.
There are some disadvantages to the whole bunch press process though – only 3 tons can be loaded into our 5000-litre press at a time (compared to 10 tons in the same press, if the grapes are crushed and destemmed). It also takes longer to load the press, and the press cycle itself is much slower and gentler. You also typically recover a lot less juice with whole bunch pressing (630 litres per ton) compared to crushing & destemming (720 litres per ton).
Crushing and destemming is a good method for processing aromatic varietals, such as Sauvignon Blanc, where there are many precursors in the skins. Producers will often crush and destem, and then leave the juice on the skin overnight before fermentation, to extract those aromatic compounds. Chenin Blanc and Chardonnay do not have those aromatics, so we prefer using whole bunch pressing.
Another potential reason for using crushing and destemming might be to lower your acidity – especially for specific varietals (e.g. Riesling) in cooler climates. When you crush and destem, a lot of potassium is released from the skins, which can bind to the acid and cause it to drop out. This is not something we struggle with here in our valley – we are looking for a lower pH – so another reason why crushing and destemming is not our preferred method for our white wines.