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When you first start making vinegar and find out that vinegar is basically spoiled wine or some other alcoholic beverage this question comes to mind.
Vinegar is produced when acetic acid bacteria (AAB) in a liquid have access to oxygen and alcohol. AAB uses the alcohol as a food source, producing acetic acid but cannot convert all the alcohol into acetic acid. Once the fermentation is complete only trace amounts (0.5-2%) are left.
There are many things which affect the amount of alcohol which is present in your homemade vinegar and with proper care you can produce a tangy flavorful vinegar with a low alcohol content.
Homemade vinegar alcohol level
Homemade vinegar will have some residual alcohol in it no matter what you do. Vinegar is made by the process of fermenting sugar into alcohol and then the alcohol into acetic acid. Until all the sugar in the liquid has been consumed the yeast will continue making alcohol.
Although this process slows down considerably as the sugar content in the vinegar falls it is never quite finished. This provides alcohol for the AAB which continues to acidify the vinegar.
At the beginning of this process the alcohol level may start out high or climb as it ferments depending on the method you are using to make your vinegar. In time the easily available sugar will be consumed and the AAB will have converted some of the alcohol into acidic acid causing the alcohol level to fall.
5 ways to reduce the amount of alcohol in homemade vinegar
When making vinegar you have various methods which have an effect on the final alcohol level in the finished vinegar. Depending on your situation you can use any or all of these methods to ensure a low alcohol content in your finished vinegar.
Reduce the alcohol content by giving it extra oxygen
It takes oxygen for the AAB to convert the alcohol into acetic acid. Two things need to happen before the alcohol can be consumed.
- The population of AAB needs to be high enough
- The oxygen needs to get into the liquid
These two go hand in hand. The more oxygen the more AAB, which requires more oxygen. When making homemade vinegar this is usually accomplished by leaving your vinegar mixture open to the air. This allows oxygen to reach the surface of the vinegar which the AAB then use.
To increase the efficiency of the AAB choose wide mouthed fermenting vessels with a low ratio of surface area to volume. Alternatively you could aerate the vinegar by mixing it, transferring it between containers or using more specialized techniques.
Ferment at the optimum temperature for acetic acid bacterial growth
AAB optimum temperature for growth is 25˚C whereas the yeasts are most active at 30˚C. Fermenting at the lower temperature allows the AAB to grow the most efficiently keeping the alcohol content low throughout the process.
If you are concerned about alcohol levels ferment your vinegar in a warm location but not above 30˚C. This helps the AAB to efficiently convert the alcohol in the vinegar into acetic acid as the yeast produces it.
Give the acetic acid time to metabolize the alcohol
Fermentation is a biologic process and although there are ways to speed it up there are limits. As the sugar content in the vinegar drops the rate it is metabolized by the yeast slows but it does not stop. This means that as long as there are fermentable sugars in the liquid there will be trace amounts of alcohol.
As the rate of alcohol production decreases the AAB have less energy to grow and their population decreases slowing the rate they can consume the alcohol. This is why vinegar always has trace amounts of alcohol.
Start with a lower alcohol level
AAB cannot grow in alcoholic solutions with a percentage of 15% or higher so if your starting liquid has a high alcohol content the AAB will have a hard time acidifying it. Dilute the starting liquid until it has a lower alcohol percentage by adding water, juice or evaporating off some of the alcohol.
One of the most popular methods of making homemade vinegar is to ferment the liquid symoltainiously as the AAB consumes the alcohol. This method keeps the alcohol level low throughout the process and allows a variety of yeast species to grow.
Not only does this provide you with vinegar which has a low alcohol level as all times in the process but it also adds unique flavors to the vinegar as the yeast produces a wider variety of esters and enzymes. As the level of alcohol remains steady for longer the AAB population has a chance to stabilize and diversify. This improves the metabolization of the alcohol.
Provide adequate minerals for the AAB
All living things need minerals to grow. Providing enough calcium and other nutrients will improve the growth of both the yeast and AAB.
When making homemade vinegar from whole fruit or fruit juice there usually enough minerals for adequate growth of the yeast and AAB but when making vinegar from mainly sugar solutions the cultures have a hard time growing efficiently. This will leave more alcohol in the vinegar for longer.
If you are making vinegar using mainly refined white sugar mixed with a little fruit solids of juice you can speed the process and lower the alcohol content by adding a packet of yeast nutrient. This will ensure there will be enough minerals and other trace vitamins needed by both the yeast and AAB.
Even distilled vinegar still has trace amounts of alcohol
Even distilled vinegar has alcohol in it. This means that the distilled white vinegar in the cupboard has trace amounts in it.
When vinegar is distilled the evaporation point of the alcohol and acetic acid is lower than that of the water in the liquid. This process will remove both the alcohol and acetic acid from the water in the solution but cannot separate the two.
This means that if you want to lower the amount of alcohol in a finished vinegar you can increase the temperature to encourage the evaporation of the alcohol but remember that you are also losing some of the acetic acid along with the alcohol.
Conditions which increase the alcohol content of homemade vinegar
Homemade vinegar should have an alcohol content of 0.5-2% which is very low and will not cause any adverse effects on anyone using it but there are ways which the alcohol level can increase past this level.
The most often way this happens is when the vinegar has been sealed before the yeast has completed its active fermentation. The yeast in the vinegar will always be present and if there is any available sugar it will use it for energy and produce alcohol.
Check the specific gravity of the vinegar before bottling it
If the specific gravity is still high then there are still sugars dissolved in the vinegar. If you bottle it when the specific gravity is high the main fermentation is not complete. This has the effect of eliminating oxygen from the AAB and preventing its growth and as a result the AAB population declines and does not consume the alcohol the yeasts are producing. The end effect is an increase on alcohol content.
Maintain an even temperature at or below 25˚C.
Keeping your vinegar in a hot location will also slow the growth of AAB but encourage the growth of yeast. Again producing an imbalance in yeast to AAB with the result of an increase in alcohol content. To ensure proper AAB growth keep your ferment below 30˚C.
