I can think of the many times there have been discussions about Cold Stabilization. Some of those discussions turned into arguments about whether it was a necessary step or one that could be eliminated. As it turns out the basis for those who didn’t think it was necessary were mostly those that were accustomed to making better grapes with excellent initial Ph and Total Acid numbers. The rest of us making Hot climate grapes were old hands at adjusting Ph and TA with substantial amounts of tartaric acid. Making those additions made the wine unstable when exposed to cold temperatures even not so cold temperatures of typical wine storage. Sometimes there was also the need to lower the TA after making a too aggressive addition. In other cases if we could get the PH down below 3.6 we had a shot of lowering the PH while also lowering the TA making the wine more age worthy. And that is how and why we did it. Some also believe that the wine clears better after a winter in the garage. I tend to think so myself. However now when we are using far superior grapes with almost perfect numbers there really is no need to alter those numbers by exposing the wine to cold temperatures. So to some extent we are abandoning the practice. Warmer winters have also contributed to less effects of CS on our wines. But , winemakers in the colder parts of the suburbs who store wine in sheds not in semi heated garages are still achieving that level of stabilization. When having club tastings of Winemakers in the club that jointly fermented wine there are differences in the tastes of these wines. The ones that have been the coldest compared to those that were not are not always better either. I came across this article that sheds more light on the process and suggests alternatives to the cold garage. I think you will find it very interesting. Some of It was completely new to me.

Cold stabilisation now

by Louis Nel

New World Winemaker Blog August 20 2010

Cold stabilisation of wine is one of those things that is very difficult to determine. When is a wine stable, and under which circumstances is it stable? The method used to determine the level of cold stabilisation will determine that. At one time the water bath method using electrical conductivity as a measure was popular, but it actually only determined the level of cold stabilisation at 0°C. The minus four degrees centigrade freezer test, determined the level of stability that the wine will have under those circumstances, and not necessarily for a longer time, and at a lower temperature.

With all these philosophical headaches to contend with, the only proper way of stabilisation was to keep the wine cold for a very long time, or to seed it with crystals at a very low temperature. The effect was that the wine was often exposed to oxygen at very low temperatures where it can dissolve very easily, but it would only react at higher temperatures. Apart from these negatives the energy usage, cost, lowered total acidity and loss of carbon dioxide gas was a worry. Often wine had to be sparged with nitrogen inline after stabilisation to push out oxygen, while removing CO2, possibly flavour, and the nitrogen itself dissolving at low temperatures, foaming when the wine is mixed at a higher temperature. The biggest drawback in future will be the energy used during this process. After this long list of negatives, one would think that there would have been alternatives by now. Well there are, sort of.

Being an avant garde winemaker in my youth, I dabbled with mannoproteins even before they hit the shelves. Here was a product that would keep all the valuable attributes of the wine, without any of the negatives of cold stabilisation. The only drawback was that it only worked so-so. The product was too dodgy to use on big Tesco orders, and the amount of comebacks was always just below the threshold for concern, but only just. At bottling time I would often find that the mannoproteins would form a slimy layer on the filter sheets, and sometimes even block a filter. This meant that some of the proteins where being filtered out. I tried to compensate for this by adding the mannoproteins during bulk filtration, thereby filtering and dosing it at the same time, but I never knew whether the difference was just in my head. All said, Australia shunned the product until other countries stopped experimenting with it.

Another alternative for stabilisation is electrodialysis. This procedure involves a membrane that, at room temperature, removes destabilizing ions, potassium, calcium, tartrate salts using quite a low current. The energy usage is very low, but the capital requirement is quite high. Many people are touting this technology as the next big thing, because it does not seem to lower the TA significantly, and also (apparently) seems to improve the sensory aspects of wine.

The latest technology that is making my tail wag is the use of CMC. CMC is carboxymethylcellulose, and it was recently legalised by the OIV. CMC is used in food as a viscosity modifier and emulsion stabilizer. CMC works the same way as mannoproteins inhibiting crystal growth, and is added to wine just before bottling. The only negative aspect of CMC is that it is not a natural product, and if not used, has a relatively short shelf-life. The OIV specified that CMC’s used for winemaking must be of wood origin, so that would help a bit for the conscience.

I hope CMC is what it is cooked up to be, because it could be a wonderful breakthrough.