One of my favourite stories from the Bible is the one where Jesus turned water into wine during the marriage at Cana. Despite this incredible event, asking most winemakers today whether they dose their ferments with water is like asking somebody about his brother in jail… you just don’t talk about it.

The International Organisation of Vine and Wine (OIV, if you parlez français) prohibits the addition of water in all of its 44 member states, which includes countries such as South Africa, Australia, Chile, Brazil, Uruguay, New Zealand, Austria, Croatia, Czech Republic, France, Germany, Hungary, Italy, Israel, Slovenia, Spain and Turkey. But why is the addition of water such a touchy topic? To answer this, we’ll have to hop into the vineyards and consider the interaction between the sun and the water content of ripening grapes.

Research done in Australia on Shiraz (Australia’s most planted grape variety) showed that ripening grape bunches can lose up to 20% of their weight (all of it water) at the end stage of ripening. The effect of the sun is obvious. This exodus of water basically concentrates sugar, which is further increased by the ripening effect of the sun. Wine producers in the southern hemisphere (i.e. Australia and South Africa) and even northern hemisphere (California) are often faced with the imbalance between grape sugars and tannins (and all the other critical flavour compounds). The problem is thus: sugars develop and build up during the harvest. Often, the heady tannins and usual aroma suspects arrive when the party is almost over, or in other words, when the grapes are already overripe. French winemakers critical of watering back wine (this should more or less include all of them) often state that sugars in their grapes develop more slowly and is thus in concert with phenolic ripeness. For an interesting debate, just mention the word ‘chaptalization’ the next time you encounter one of these winemakers.

Winemakers fiddling with overripe grapes can encounter various problems. Simply put, high sugar musts can lead to stuck ferments, even when inoculated with commercial yeasts. If the commercial yeast does however have a sweet tooth and is impervious to high alcohol levels, a high alcohol wine can result, where an alcohol level of 15% or higher is common. The Lower Alcohol Lobby frowns upon high alcohol wines (for various health, safety and other socio-political reasons) and is a powerful driving force behind many health initiatives and various research projects at leading universities. Another factor is tax that is levied on alcohol in some countries.

What is a winemaker to do, apart from having grapes picked earlier and fermenting with yeasts that have a lower alcohol conversion factor? (The latter doesn’t really exist.) There are a few techniques available, of which adding water to wine is paramount in this blog. But you will have to wait for part two of this blog to read all about these controversial techniques.

Bernard Mocke is a technical consultant for Anchor Wine Yeast.