Monday, October 24, 2011

Stuck ferment

A rich and ripe harvest
2011 has been a fantastic year in the Languedoc and here in Faugères we have been blessed with some lovely fruit. We did have some problems with powdery mildew (Oidium), which meant that we had to be very selective in some vineyards, but generally the fruit that we processed was of very good quality. The quantity was also up over most of our vineyards. Cinsault, Grenache and Carignan were the best performers with almost double the yields that we have had on previous years. The yields caused us some concern at the start of harvest as we did not know if we would get all the fruit ripe. Fortunately this was not the case and we had one of the driest harvests that I have ever done!

The curse of the sun
I have said often that Grenache is a very difficult variety to work with when you have a hot year. What can happen is that a heatwave can push the sugars up very quickly while the skins remain unripe. The resulting wine will have high alcohol, green tannins and no colour. 2011 was strange in that while the temperatures were high, the nights were quite cool. Therefore the grapes had some lovely balanced ripeness. The problem that we had though was that we could not get all our grapes off the vine before the sugars went crazy.

Stuck ferment
I really like ripe Grenache. I think it needs to be hung on the vine to get that dark cherry confectionary character. As a stand alone wine it can be too much but it blends beautifully. That said it is often difficult to nurse ferments through when the potential alcohol is high. We only do natural ferments which makes life even more interesting. So our ferments were looking really good and smelling great. The temperatures were under control, there was plenty of nutrients for the yeast but the alcohol just became to much and the ferments slowed to a crawl. Yeasts are very much like humans. They reproduce when there is plenty of food and the temperatures are good. But they also create so much waste, alcohol, that it starts to kill them!

Winemaking to the rescue
What I usually do when ferments slow down is firstly make sure the temperatures are around 26°C. This is not always easy as we are usually well into Autumn by the time you start having problems. Luckily all our ferments are in one tonne lots so I just wheel them out into the sun when the sun shines. If the temperatures don't push through the sugars then I will search for a ferment that is finishing strongly and drain off the wine. Then I will press the struggling ferment and flush the pressed wine over the active skins. This usually works but every now and then you have to be more radical.

Pied de cuve
This is the last resort and if it gets to this stage then this must work. What you do is basically cook up a small ferment that has the same conditions as your larger cuve. You do this by adding sugar, yeast food and a special strain of yeast called Bayanus which ferments to high alcohol levels. Then you slowly homogenise the pied de cuve with your struggling ferment. Then pray!

The disaster of residual sugar
The reason that it is so important to convert all the sugar to alcohol is quite complex. Basically all the bacteria and spoilage yeasts in wine love the conditions surrounding a stuck ferment. Acetobacter (volatile acidity) and Brettanomyces (viscious spoilage yeast) love these conditions and these will both destroy your wine. The bottom line is don't let the ferment stop but if it does it is very important to be pro-active in getting them going again. My praying is working and this week I press the last of my ferments and I can then sleep easy.





A Vigneron in distress

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