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Due to the variability and fluid characteristics of homemade kombucha it is difficult to determine what the final alcohol content of it will be. There are some methods which can give a good idea to the potential percentage but without expensive measuring equipment exact measurements are impossible to determine.
Factors which affect alcohol percentage in homemade kombucha.
The sugar concentration
The amount of sugar dissolved into the tea will determine how much alcohol the yeasts can make. The more sugar the higher the potential alcohol content the kombucha can have. The sugar concentration in a liquid is measured using a hydrometer which measures the specific gravity of a liquid compared to that of water.
In wine or beer making this is straight forward as the only cultures which are promoted are specific yeasts which produce a known amount of alcohol but when it comes to kombucha the yeast cultures are fluid and may change depending on time of year, location and history of the scoby.
The active yeast cultures in the kombucha
It is the yeasts in the kombucha culture which convert the sugar into alcohol and carbon dioxide. There are thousands of different yeast cultures which all have different characteristics. Some produce high amounts of alcohol where some produce little.
The amount of alcohol found in kombucha is dependent on the types of yeast present in the starter and surrounding area. Some yeasts like Saccharomyces cerevisiae produce high amounts of alcohol where others like Metschnikowia pulcherrima produce organic acids and carbon dioxide. This influences the amount of sugar which will be converted into alcohol.
Most yeasts can tolerate an alcohol content between 8-13% which is higher than kombucha will reach given the typical sugar concentration of the sweet tea.
The ambient temperature of the room
Kombucha starter is made up of a collection of bacteria and yeasts which consume the available energy in the form of sugar and convert it into different byproducts. Yeasts produce alcohol, bacterial cultures produce organic acids and two of the most prevalent are lactic acid and acidic acid.
Lactic acid bacteria use the sugar in the sweet tea as energy and are therefore are in direct competition with the yeasts for food energy. This leaves less sugar for the yeasts to use for production of alcohol.
The ambient temperature of the room is important because most lactic acid bacteria are happy at cooler temperatures whereas the yeasts are most active at higher temperatures.
Since it is the yeasts which produce the alcohol when the temperature of the kombucha culture is conducive for its growth then the yeast will consume more of the sugar producing more alcohol.
The amount of active acetic acid bacteria
Acetobacter is the bacteria which is the bane of the wine and beer making industry. It converts alcohol into acidic acid spoiling the wine (or converting it into red wine vinegar). With a culture which has a high amount of acetobacter active in it the alcohol content will be lower due to the conversion of the alcohol to acidic acid.
It is the Acetobacter xylinum which is believed to be the bacterium which synthesizes the cellulose which makes up the SKOBY and is one of the most prevalent bacteria in kombucha.
Length of fermentation time
The fermentation time affects the alcohol content in two ways. The alcohol content will rise until it reaches a peak determined by the amount of sugar in the solution, the type of yeast and the amount of other active bacterial cultures which are competing for the sugar.
Once it hits its peak it will begin to decline as the acetic acid bacteria convert the alcohol to acetic acid.
In the short term the yeasts will grow fast producing a large amount of alcohol and carbon-dioxide, after a few days they will reach a maximum population and start to saturate the kombucha. This will last a week or so until the yeasts and other microorganisms have consumed most of the freely available sugar.
Then the fermentation will slow and the amount of alcohol the yeasts produce will slow. It is at this time that the acetic acid bacteria will really start to grow. They will have their energy source, alcohol, and oxygen which they need of growth. This is when the kombucha begins to taste like vinegar and when the alcohol level begins to level out and drop.
Amount of surface area exposed to the air
The acetic acid bacteria in the kombucha need oxygen to grow. If the container used to make it has a wide mouth and is covered with a thin cloth which allows air to flow freely through it the acetic acid bacteria will have the greatest chance of growing and converting the alcohol into acidic acid.
When making wine or beer the fermentation is done in an anaerobic environment which reduces the chance of acetobacter from growing and converting the alcohol into vinegar. This is done by placing the maturing wine or beer into a carboy with an air lock. Kombucha is made in an aerobic environment for the main fermentation. This adds the traditional tang to it but it also helps to reduce the alcohol content.
If the kombucha is second fermented into a soda the yeasts get another chance to grow and convert sugar into alcohol. It is then that the alcohol content can rise substantially if too much fermentable sugars are added.
Ways to reduce the amount of alcohol in homemade kombucha
Kombucha is a dynamic drink which contains a wide variety of microorganisms in it which react differently to changes in their environment. To reduce the amount of alcohol in your kombucha is simple but each change will change its flavor so you may have to experiment a bit to get what you want.
Limit sugar concentration
Lowering the sugar content is an obvious method as it is the food which the yeasts use to grow, but to make kombucha safely you need at least 50g of sugar per liter of tea. This will provide enough energy for the bacteria and yeasts to grow fast enough to keep any pathogenic bacteria from entering the culture.
Control fermentaiton time
Extending the fermentation time will lower the alcohol level once the yeasts have reached its maximum population level. The alcohol will be consumed by the acetic acid bacteria but they will produce acidic acid. Fermenting your kombucha too long will produce kombucha vinegar which is not pleasant to drink (although it does have other uses).
Maintain a temperature range of 22-30 Degrees Celcius
Keeping the temperature below 30 degrees helps the lactic acid bacteria to compete with the yeasts for the available sugar. This prevents the yeasts from using all the sugar to make alcohol which lowers the potential alcohol concentration.
Controling the alcohol content during second fermentation
- Limit the amount of additional sugar added
- Reduce the fermentation time before refrigeration
- Keep the temperature below 30 degrees Celsius
Is it possible to get drunk on kombucha?
Store bought kombucha is considered non-alcoholic with an alcohol concentration of 0.5% so the likelihood of getting drunk on it is slim to none.
Homemade kombucha on the other hand can have an alcohol concentration of up to 3% so it is possible if you made a dedicated effort to drink excessive amounts of it. The concentration of the alcohol makes it difficult the raise your blood alcohol level above 0.08 even at a concentration of 3%. Concentration is important because alcohol is absorbed into the body faster at higher levels, as the concentration drops so does the speed which it is absorbed.
There are two ways the alcohol can get into your blood stream.
- Through the stomach wall
- Absorbed by the small intestine
The stomach absorbs only a small percentage of the alcohol especially at lower concentrations. This is why the effects of alcohol are not felt as quickly or severely if it is taken with food. When you eat something with your drink the stomach digests the food for a while before passing it to the small intestine. This slows the absorption of the alcohol.
The small intestine absorbs the remaining alcohol which is passed through the portal vein to the liver. The liver will breakdown the alcohol at a rate of about one standard drink per hour which is defined as a beverage which contains 0.6 fl. Oz. or 14 grams of pure alcohol. If the liver cannot break down all the alcohol sent to it the blood alcohol level will begin to rise.
To get 0.6 fl. oz. or 14 grams of pure alcohol with an alcohol level of 3% (the high end) you would have to drink 19.4 fl. Oz. of kombucha every hour for a sustained period of time. This is why it is hard to get drunk on lower alcohol concentration drinks like kombucha.
Warning: Even the smallest amount of alcohol can affect your reactions. It is not recommended that you drink any alcohol while operating equipment including a vehicle. Instead drink your homemade kombucha at home with a meal at least an hour before you drive.
