Now that your wine has gone through its paces and is stable and filtered, it is time to decide what you want to do with it, and when you want to bottle it. Once you make these decisions, you can do your next filtration, prepare the wine for bottling, do your final pad filtration, and send it off to the bottling line. Let’s look at each of these steps one at a time.
When I say that you have to decide what you want to do with the wine, I am basically talking style. Is this going to be a dry wine, off-dry, sweet, or will another wine be blended with it? (It is very common to blend small amounts of other wines into a base wine to give it added complexity, aroma, balance, and other characteristics, but that is a topic for another post.) You have to take into consideration what you are trying to accomplish and how much the base wine can contribute to the finished product. Is this something for your personal consumption? Are you trying to reach a certain consumer base, maybe sweet wine drinkers? At what point does the wine balance sweetness and acidity? This is important since too much sweetness with too little acidity creates a dull, flat wine. I will explain how to do trials to help decide how far you can go with sweetening, in my next post.
If the wine is to be dry and unblended, all that needs to be done is a filtration through the next two tighter sets of filters. As mentioned in previous posts, I like the Beco filters made by Begerow. For the filtration off of the tartrates, I used the Beco KD3 filter pads, a fairly coarse filter at 2.5 microns, as the wine is generally pretty cloudy at that point. Anything tighter would clog up the filter. For this next step, I would use the Beco KDS15 filter pads. These have a micron rating of 0.7. These filters will polish up the wine to the next level. The third, and last, pad filtration I do, is with Beco Steril S80 pads, which have a rating of 0.2. I will mention here that I am talking about white wine. I do not use the Beco Steril S80 on red wines unless I have sweetened them, because I don’t feel it is necessary to filter dry red wines that tightly as it may strip some of the color and flavor.
It is important that each time you filter, you test the sulfite level to make sure there is enough to keep the wine from oxidation. At this point, with sulfite adjustments all along the way, the wine is ready to bottle. There will be one more final filtration on the way into the bottling line using what is rated as a 0.45 micron absolute cartridge filter (see below) .
In case you are confused as to the tighter rating on the Steril S80 pad filter, at 0.2, as apposed to the 0.45 micron cartridge filter, there is an explanation. The ratings on the pad filters are what is known as “nominal”, which means there is actually a range of porosity and some particles larger than 0.2 microns can get through them. A micron cartridge filter, however, can be an “absolute” filter. The term “absolute” means that nothing bigger than a 0.45 particle will get through, making it a much more sterile and accurate type of filter. Absolute filters are only used as finishing filters, as they are very tight and the wine has to have gone through several “clean up” filtrations before it can pass through an absolute filter. In addition, they are very expensive, so you want to get through as much wine as possible...the cleaner the wine, the more throughput. I also want to point out that pad filters only come in nominal ratings. It is the nature of the construction of a pad filter, and what goes into the construction, that dictates this situation. For absolute filtration, that will be certain to take out every last yeast cell and potential spoilage organisms, you need an absolute cartridge filter.
If you decide to sweeten the wine, there is a bit more involved. My next post will address calculating sugar and continuing through filtration.