Deciding when to bottle your wine can be tricky. There is no one size fits all timeline, but there are some factors that should be taken into consideration. No matter what the wine type, it should appear crystal clear by the time of bottling. The wine should also be "stable" so that no unexpected processes occur inside the bottle. Most white wines will be bottled relatively early, when the fruit is still vibrant and expressive. Red wines often are left to age in bulk until the aggressive tannin starts to round out and the wine comes into balance. Beyond the basic timing considerations, you may choose to bottle your wine because the tank, barrel, or carboy is needed for another wine that has just finished fermenting. I will often bottle a few wines in the fall to free up space for the new batches but only if the wine is ready. Here are the main drivers that will influence my decision on when to bottle.
After fermentation has completed, microscopic particles like grape pulp bits and yeast will begin to fall out of suspension. As this happens, the wine will appear gradually more clear and a light dusting of sediment or "lees" will coat the bottom of the storage vessel or carboy. This process can be accelerated with fining agents or filtration, but I generally like to let the wine clear on its own (Many fining agents/filters can also strip desirable characteristics from the wine). Eventually the wine will become crystal clear. This is easy to spot in a white wine. In a red wine, a flashlight can aid in checking for clarity.
A wine that is not clear will eventually clear up in the bottle, leaving sediment behind. If back sweetening is performed on a cloudy wine, it will likely re-ferment in the bottle, causing corks to go flying.
Most wines will clear up within 3-6 months after fermentation.
A wine that is not cold stable, will create potassium bitartrate (Cream of Tartar) crystals in the bottle. Cold stabilization can occur quite well naturally if your wine storage area gets cool (<55°F) for a long enough period of time, like several months of the winter. To quickly cold stabilize a wine, chill between 27°F and 35°F for about a week. This will assure that any crystals will fall out before the wine goes to bottle.
If you do end up with a few crystals in the bottle, don't worry... they are unsightly but harmless. I see this all the time with store bought bottles and am usually a little cautious when pouring the last glass from a bottle.
Whether it is a red wine, white wine, potato wine or tomato wine, it needs to be microbially stable before going into bottle. There are a handful of bacteria that can cause you trouble. Some should be encouraged to do their business before bottling and some should be discouraged all together.
If the wine is intended to be dry, I do everything that I can to encourage a complete alcoholic fermentation. This means keeping the wine warm (~70-75°F) as the fermentation is wrapping up, providing adequate nutrient, and giving the wine a little air and circulation during active fermentation. If all of the sugars have been consumed by the yeast, there is no risk of re-fermentation in bottle.
If you intend to back sweeten, be sure to use an inhibitor like potassium sorbate to stop any yeast from budding and multiplying into a sizable colony again. Even a clear wine can have enough yeast present to kick off a new fermentation if sugar is added. A cloudy wine will likely re-ferment even if potassium sorbate is added.
On red wines, I virtually always will allow malolactic fermentation. This the process when malolactic bacteria converts malic acid (sour) to lactic acid (smooth). Malolactic fermentation will usually occur naturally, even if you don't add a bacteria culture. If it happens in the bottle, it will cause a slight carbonation, and sizable change the taste of the wine. To assure that it happens before bottling, I prefer to add a reliable bacteria strain right after primary fermentation. To encourage a complete malolactic fermentation, keep the wine warm (~70°F) for a month or so after adding the bacteria. Also, do not sulfite the wine beyond about 15 parts per million at until you are sure the malolactic fermentation has completed. Once complete, the wine will stop bubbling all together.
On white wines, I generally like to prevent malolactic fermentation. This can be achieved by sulfiting immediately after primary fermentation is complete and maintaining adequate SO2 levels. Lysozyme can also be used to prevent malolactic fermentation but I have not found it to be needed as long as the pH is less than 3.4.
Paper chromotography kits can be used to test for the presence of malic acid. On larger batches this is something you should do, but it can be cost prohibitive on smaller batches.
The most prevalent spoilage bacteria is acetobacter. If you haven't encountered it yet, you probably will. The bacteria is carried on the feet of fruit flies and is most likely already present in your wine, just waiting to wreck your day.
Acetobacter is responsible for creating acetic acid (vinegar), acetaldehyde (sherry smell), and indirectly responsible for ethyl acetate (nail polish remover smell). To prevent the bacteria from doing it's work, the wine needs to be protected from oxygen during the aging period and beyond. Topping carboys up to the neck and keeping airlocks full is a very reliable way to keep oxygen contact at a minimum. Inert gasses like argon, nitrogen, or CO2 can be used to blanket the wine for shorter periods of time.
Maintaining SO2 levels during the aging period is also important in preventing damages from spoilage bacteria. SO2 reacts readily with oxygen, helping to scavenge any little bit that gets in the wine. SO2 also helps to create an environment that is unfriendly to spoilage organisms. By taking steps to prevent acetobacter, you are also providing protection against the less common spoilage organisms.
Bulk Aging Time
Most red wines should be allowed to age in bulk (pre-bottle) until the rate of maturation begins to level off. This usually takes between 8-12 months. During this time, oak adjustments can be made and the wine can be carefully blended with other similar wines until it is just right. Allowing the wine to age through one winter and one summer cycle assures that the wine is relatively cold stable and any last minute yeast or malolactic related bubbling will occur before bottling. Sometimes the little bit of sugar imparted from oak can be enough to cause a few bubbles as the basement warms up again in the summer.
White wines are often bottled before the dissolved CO2 has time to dissipate, and will need a little degassing. Aggressive stirring and splashing will achieve this, or a small vacuum pump can be used.
Assuming the wine is stable and clear, I recommend bottling white wines at around six months. In the northern hemisphere this usually means around April or March which is just in time to have the wine ready for summer. Once in bottle, give the wine a month or so to recover from any temporary bottle shock.
For red wines, I like to make sure the wine has gone through at least a partial summer and a partial winter cycle which means about 9-12 months. As I am beginning to bring in grapes for the fall harvest, I am also bottling wines to free up carboys. This works especially well for wines stored in barrels, so that the barrel does not need to be stored and maintained between wines. I also trust my red wine taste buds better around September and October as the air begins to cool. A blend that I make during the hot summer months is likely to be a little off target for what I want to be drinking around Thanksgiving.
With juice concentrate kits, bottling can occur VERY early. As soon as the wine is clear, it is about ready, which can take as little as 6 weeks for a kit. The downside is that many kits will "wimp out" after about six months or so. Aside from high end wine kits, I would recommend bottling early and drinking them soon.
If you don't want to mess with bottles, don't forget you can always keg the wine!
If you have any tricks, tips, or questions post in the comments section below.
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