Saturday, November 16, 2013

2013 St. Croix rose' wine Edmonton cold stabilising

The St. Croix finished fermenting on the 71B yeast and started to settle out quickly.  I racked it into a new carboy and it is now out in the cold garage and in the process of cold stabilisation.

Cold stabilisation is storing the wine at a temperature between 0 and -4c for at least two weeks and helps with both the clarification of the wine and reduction of tartaric acid by precipitating it out of the wine as tartaric acid crystals. You can even go to colder temperatures but below -8 the wine may freeze depending on the alcohol content and wine chemistry.  Tartaric acid crystals are not uncommon in bottled wine and are sometimes referred to as wine diamonds.  You may have found these in some bottled wines when you pour out the last remnants of the bottle and some granular sediment pours out also.  These wines were likely bottled before cold stabilisation was done and after the wine was bottled it was exposed to cold temperatures at some point and the tartaric acid started to form crystals in the bottle. I don't find these "wine diamonds" appealing in my wine so try to eliminate them. Here is the St. Croix rose in the 11 ltr carboy and you can see the crystals have formed at the top surface.
One of the issues with growing grapes in cold climates is the likelihood of high acid content in the juice. However the cold climate is also convenient for conducting cold stabilisation on the wine as in late fall after the fermentation I can just set the wine out in the garage as the temperatures in late October/November and December in the garage are perfect. Cold stabilisation is one method to help reduce the acid and simply storing the wine in the cold temperatures causes tartaric acid to precipitate out of the wine.  They form throughout the wine and sink and here you can see they have formed on the surface of the wine at the top of the carboy (photo below) and if you were to bump the carboy they would sink to the bottom;
and also on the bottom of the carboy.

One of the added benefits of the tartaric acid crystal forming on the bottom is that the crystals actually can form a mat that seals over the sediment on the bottom and makes it easy to rack to the next stage.  Our next stage will be racking the wine once more, adding a slight amount of liquid sugar for touch of sweetness and also sorbate to prevent new fermentation of the sugar.  We'll bottle after that.