There are many ways a winemaker can influence the final alcohol of wine before fermentation, during fermentation, and after fermentation. This essay will look at these three stages of the winemaking process, addressing the various methods that can be employed to increase or decrease the final alcohol level of a wine and why they might be considered useful. There are many reasons for a winemaker to alter the final alcohol level of a wine: to achieve a certain style of wine, to meet customer demands, for legal and taxation reasons, and for microbiological stability.
The decision to pick early may be made by a winemaker, particularly in warm regions, in order to minimize sugar levels and potential alcohol levels, as well as to retain acidity. Mauricio Lorca makes a Torrontés from La Rioja, Argentina, picking one parcel early and one parcel at full physiological ripeness and blending the two to balance alcohol levels. However, early picking to reduce potential alcohol levels is not always judicious, particularly with red wines, as it can result in unripe tannins and green flavors. In some hot climates where ripe grapes attain naturally high brix levels, water may be used to dilute the must. However, this technique increases the pH of the must, which negatively affects microbiological stability and dilutes concentration levels (though there are also winemaking techniques to mitigate these effects). While allowed in the US, Australia, and other regions, adding water is not permitted for wines sold in the European Union, with the exception of water used for the purpose of incorporating additives. Yet the total volume of water to wine for the addition of additives is as high as 7% in Australia, far more than is necessary, which could reduce alcohol by 1% ABV, if the full allowance were used.
Conversely, if grapes have attained low brix levels due
Hi Rebecca. Thank you for easy to follow explanation on the subject. Just one thing I did not quite comprehend. You mentioned that 'watering down' must/juice "increases" the pH of the must. However, while water dilute acidity (which increases pH), it also dilute sugar as well. So wouldn't it remain at the same (high) pH (it started with)? Or watering down somehow dilute more acidity than sugar? Many thanks for your feedback in advance.
Adding water dilutes the sugar and the acidity (and increases pH). Many winemakers add a small amount of acid along with the water to maintain juice acidity.
Adding water dilutes the sugar and titratable acidity (TA) in the same proportion. I'm not quite sure what it would mean to increase pH "equally" as it is a completely different scale (pH is a logarithmic scale), but what's important is just that the pH may increase slightly.
From your comments, it seems that you are assuming that the juice is both high sugar and high pH. This is not always the case. While sugar and pH both increase throughout ripening, one reason a winemaker may choose to pick at higher Brix is to wait for the acidity to decrease (or pH to increase). For example, I've seen Sauvignon Blanc at 24 Brix with a pH of 2.9. This pH is low enough that fermentation struggles but the sugar is a bit high.
If a winemaker chooses to add acidified water (water with tartaric acid), only a small amount of acid is required (less than 0.5 g/L). Please note that this is not done universally.
Adding water dilute BOTH sugar (decrease alcohol) and acidity (increase pH) equally wouldn't it?
Also adding tartaric acid is another method to control pH (decrease pH) to a small point (cannot add much as it will change the wine's profile and make-up).