Wine has a culture of its own which has quite a few elements that anyone can genuinely enjoy taking part in. A part of this culture that can be just as enjoyable as drinking wine is winemaking.
Winemaking is not limited to just wineries, it can be done right from the comfort of your own home, giving you autonomy over the taste of the wine you are consuming. It’s important to know everything that goes into winemaking from big details to small ones if you want the wine to come out just how you like it.
If you’re looking to get into winemaking, one major detail is the process of wine fermentation, specifically how to stop it. There are several ways to stop the process of wine fermentation and they are all based on how sweet or dry you would like the wine to be.
What is Wine Fermentation?
After they are harvested, wine grapes are crushed for their juice, which will turn into wine during the fermentation process. Wine fermentation happens when yeast consumes and converts sugar into roughly half CO2 gas and alcohol by weight. This yeast can be added in or simply just the natural airborne yeasts that are associated with grapes.
With the alcohol content increasing in the wine, the sugar content decreases which makes the wine drier. How much alcohol will be in the final product of the wine at the end of the fermentation process is dependent on the amount of available sugar.
Due to this, harvesting your grapes at the right time is imperative, as many contain lower sugar content, so you want to catch them at the desired ripeness. There are two distinct stages of wine fermentation, primary and secondary.
Primary fermentation is also referred to as aerobic fermentation because the vessel for fermentation can be open to the air. This air is beneficial and important to yeast cells multiplying. Primary fermentation has a usual span of the first three to five days of the process.
During the first few days, about 70 percent of the fermentation’s activity will take place. It is common for a good amount of foaming to happen during this stage.
The remaining 30 percent of fermentation will happen in the secondary fermentation stage. This fermentation stage is much slower than the primary fermentation stage.
Secondary fermentation can take up to one to two weeks depending on the nutrition amount as well as the amount of sugars still available in the wine. Air exposure during this stage should be kept to a minimum as it is an anaerobic fermentation.
This decrease in air exposure will cause the yeast to give all its energy into making alcohol instead of focusing on multiplying. All you need to do to maintain minimum air exposure is to airlock the fermentation vessel.
When Is Fermentation Over?
The process of fermentation is considered to be done when the wine goes dry at 0 degrees Brix or when it has reached the level of sweet/dryness you desire. Dry wines are usually in the range of 0.2 to 0.3 percent, 1.0 to 5.0 percent for off-dry wines, and sweet wines fall usually in the range of 5.0 to 10 percent.
So to make note again, the purpose of the wine fermentation process is to produce the actual alcohol content of the wine through yeast consuming and converting sugar into CO2 gas and alcohol. How sweet or dry your wine will be is dependent on the wine fermentation process. This is why knowing when and how to stop it is important and possibly the greatest challenge you will have in winemaking.
How to Stop Wine Fermentation?
There are several ways to stop wine fermentation. It can be stopped naturally or by manipulation. Obviously, how dry or sweet you wish your wine to be will be the determining factor in whether you want to let fermentation stop naturally or through manipulation. Here are four methods to stop the process of fermentation in wine.
Wine Fermentation’s Natural Stopping Point
If you prefer for your wine to be heavier on the dry side, letting fermentation get to its natural stopping point will be a good way for you to go. Fermentation has two natural stopping points.
One way that fermentation stops naturally is when there is nothing left for the yeast to ferment because the sugar has run out, fermentation will stop. There is no more alcohol at this point that can be produced. This wine will be dry without any residual sugars.
The second way fermentation comes to its natural stopping point is when the yeast is killed by high alcohol content. Natural yeasts associated with grapes have different levels in which they can survive certain alcohol content conditions. There are some yeasts that will die out when alcohol levels are below 10 percent which is definitely not something you want to happen if your desired wine is on the dry side.
Due to this, winemakers will add extra yeasts guaranteed to survive high alcohol levels. Saccharomyces cerevisiae is the most common yeast to add as it is very predictable. Saccharomyces cerevisiae can tolerate high levels of alcohol, usually up to about 15 percent. Saccharomyces bayanus can survive up to a whopping 17 to 20 percent alcohol content level. It can be noted that adding yeast may not be considered a “natural” stopping point to some.
Stopping Fermentation With Cold Shock
Cold shock is the only method when stopping fermentation that does not have a heavy influence on the taste, aroma, potency, or sweetness of the wine itself, making it a preferred option.
Whereas a hot temperature will speed up the fermentation process, cold temperature slows the fermentation process down. Yeast fungi go into the state of hibernation (anabiosis) and precipitate out from the bottom at a temperature of 50 degrees Fahrenheit (10 degrees Celsius).
Steps to follow
- For three to five days place your wine in a cold room or in a refrigerator at about 36 to 50 degrees Fahrenheit (2 to 10 degrees Celsius). It is important that the wine stays above the freezing point so if you are going to let your wine sit in a cold warehouse it is essential that you pay attention to the temperature constantly.
- Once the fermentation process has completely stopped there will be sediments at the bottom from the yeast that has precipitated. To get this sediment out, rack the wine into another sterilized container with a temperature of a maximum of 61 degrees Fahrenheit (16 degrees Celsius).
- After this, filter the wine with a wine filter into another sterilized container.
- Once you have filtered the wine let it sit at normal temperatures for about a week at minimum, checking on it daily. If fermentation is happening again you can simply repeat the process.
Fermentation happening again is the downside of this method of stopping fermentation due to there being no guarantee that all the yeast will get filtered out with the sediment. This can be prevented by adding around 0.14 ounces of sulfur trioxide for every 1.6 gallons of wine. Adding preservatives for home winemaking is not the best option and can also lower the quality of the wine.
Stopping Fermentation With Alcohol
If you are looking for a simple and less time-consuming way to stop fermentation this is the method for you. Stopping the fermentation of wine with alcohol is the most effective method if you want to prolong the shelf life of the wine. When the alcohol content is around 14 to 16 percent the yeast stops its function.
Remember though, depending on the yeast strain, some can survive up to an alcohol content of 18 percent. In order to stop the wine fermentation, you simply add extra alcohol to the wine.
Steps to Follow
- Choose what alcohol you will use to add to the wine. A grape distillate is the preferred option but you can also add in either vodka or brandy.
- Remove all the sediment from the wine by racking the wine into a sterilized container.
- Add your choice of alcohol into the wine until the alcohol content level is about 16 percent. (If you are unsure of the initial content of sugar for the wine you will not be able to get as accurate of a calculation of the potency from the fermentation process. If this is the case 10 to 15 percent of alcohol should be added to the wine.)
- Let the wine sit at a minimum of a week and check to see if there may be signs of fermentation happening. If fermentation is happening, simply rack the wine once more and then proceed to bottle.
The real downside to adding alcohol to stop wine fermentation is that it will alter the flavor of the wine and can change the aroma. A large part of the wine drinking experience is the aroma of the wine, so you could lose out on even more precious flavor through the smell alone.
Stopping Fermentation Through Pasteurization
Pasteurization may be the most effective way to stop the fermentation process, but it is not necessarily recommended in a home setting.
At temperatures that exceed 104 degrees Fahrenheit (40 degrees celsius), wine yeasts die. The wine will have to be heated above the yeasts’ surviving point in order to stop the fermentation process.
Steps to Follow
- Remove the yeast sediment by racking the wine into a sterilized pot.
- According to how strong the wine is, heat the wine to 131 to 158 degrees Fahrenheit (55 to 70 degrees Celsius). The stronger the wine is, the lower the temperature should be. This heat will destroy the yeast and also organisms that are hazardous which can survive in extreme conditions. You will want to keep the wine heated for around 10 to 20 minutes.
- After about 10 to 20 minutes it will be time to cool down the wine. As quickly as possible, you will want to cool down the wine to a temperature of 50 to 61 degrees Fahrenheit (10 to 16 degrees Celsius).
- Lastly, bottle wine immediately and seal the bottle.
Note: As an alternative, you could rack the wine into a bottle instead of a pot and pasteurize the bottle then seal it off.
Although this method is the most effective to stop the fermentation process, there are a few downsides.
For one, it is hard to maintain the constant heat required for this method for 10 to 20 minutes and it is also difficult to cool down the wine quickly enough. The constant heat required for pasteurization is also the cause of another downside because it is harder to do at home.
Wineries will have the facilities to do this, but for any at-home winemaker, this probably will not be the best method for you. Wine is a very temperature-oriented beverage and because of this, heating the wine to this extent will alter the flavor and aroma in some shape, form, or fashion. With this method, you risk overheating the wine which will ruin all the work you have put in.
Whether you are making wine at a larger facility or at home, wine fermentation happens none the less and it is important to know how to stop it. The fermentation process can make or break the wine you have created so it is essential to use a method to stop this process that you are comfortable with and knowledgeable of. How sweet or how dry your wine is to come out is all based on this.
For a dryer wine, you want to wait longer before stopping the fermentation process and vice versa for a sweeter wine. Fermentation will naturally stop on its own but you can manipulate the process by pasteurization, adding alcohol, or doing a cold shock. Always choose the method you believe you can handle to achieve the end goal of taste and aroma that you want for your wine.