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Kombucha Carbonation: How Does it Work?

By: Brew Your Bucha Posted: February 15, 2018 in Kombucha

One of the most appealing things about kombucha is the carbonation on the tongue as it is consumed.  As humans we crave the bubbly sensation carbonated drinks provide, leaving us with a refreshed, satisfied feeling.  So where does kombucha carbonation come from? and how do I get more carbonation in my brew?

To answer these questions, we will take a step back and discuss the science of carbonation in relation to kombucha.

SCIENCE OF CARBONATION

Most of us are familiar with the tingly bubbles that are felt when drinking sodas, sparkling water and other carbonated beverages.  The active ingredient being CO2 or carbon dioxide.  CO2 is a colorless tasteless gas which is naturally occurring in our atmosphere and experienced in our every day life.  We breathe it out, plants absorb it in.  We have put it in our drinks for hundreds of years.  However, there is a major difference between how how these sodas are carbonated in comparison to naturally carbonated drinks like beer and kombucha.

For sodas, the manufacturer puts the product through a process called forced carbonation.  This is where carbon dioxide is injected and dissolved in to the liquid.  At the root of force carbonation is two simple requirements:

  • Pressure
  • Low Temperature

PRESSURE

Carbonation intensity is influenced by the amount of pressure that is applied to the liquid.  If the gas is forced in to a liquid in a contained environment, the more pressure built up from CO2 will result in more being dissolved in to it.  It is important that there are no opportunities for the gas to escape from the container in order for the CO2 to be efficiently and completely dissolved.

At a certain point (called the equilibrium) the liquid becomes fully saturated where the dissolved CO2 gas cannot escape from the liquid, and external CO2 gas can no longer dissolve in to the liquid.  If you like the feeling of a very carbonated drink with a hard bite to it, then you seek a drink with fully saturated carbon dioxide.

LOW TEMPERATURE

Low temperature is also an important factor in dissolving CO2 in to a drink.  CO2 is dissolved much more efficiently in cold liquid than it is in warm liquid.  This means that intensity of the carbonation is dictated by the temperature in which the CO2 is being dissolved.

Think of it like trying to dissolve sugar in to cold or hot water.  At hot temperatures, the sugar melts and dissolves in to water much quicker than if you were trying to do the same thing in cold water.  Dissolving CO2 is the same principle except in opposite temperatures.  Soda makers recommend force carbonating at 45° Fahrenheit or 8° Celcius to have optimal results.

At 8° Celcius, a litre of water can absorb about 0.1 ounces (or 3 grams) of CO2. At a temperature of about 15°C, that falls to just over 0.07 ounces (about 2 grams).  This means that at 8° Celcius there is a 50% improvement in the ability to absorb carbonation with only a 7° change in temperature.

CARBONATION IN KOMBUCHA

The key difference with kombucha or other fermented drinks is that carbonation is created naturally.  In kombucha, the process of yeast consuming sugar and tea yields carbon dioxide and alcohol.  In the first fermentation, the majority of the CO2 gas is allowed to escape from the top of the brewing vessel, leaving it flat.  This is why the second fermentation process is necessary to add the fizzy bubbles that everyone craves.

However, carbonation created from natural fermentation typically does not have the same “bite” or hardness as soda.  This is because force carbonation is designed to push the beverage to the equilibrium point, or full dilution of carbonation.  Your standard home brewed kombucha can get fizzy, but usually has a softer “bite”.  You may also notice that many brewers have issues with the carbonation overflowing from their bottles, similar to a warm soda after being shaken.  This is because the CO2 has not fully dissolved in to the kombucha, and much of it is able to escape once the pressure is released.

Does this mean that brewers can never have the same carbonated bite in their kombucha as soda? not at all.  We will explain the process for you here to try.

HOW DO I GET MORE CARBONATION?

Many people are happy with a slightly fizzy drink but others have asked us how to get even more carbonation.  This is possible with proper equipment, some patience, and a proper understanding of carbonation. This is the reason we gave you a brief history on the science of carbonation, so you can apply it to your brewing techniques.

PRESSURE

Like force carbonation, there needs to be pressure created and contained within your second fermentation bottles.  This means that you need proper bottles (shown below) such as our swing tops or Amber bottles with phenolic and polycone lids which will ensure a tight seal.

Take a look through our accessories section of our shop if you need some for yourself.  A proper seal will allow the carbonation to build without a leak continuously letting out gas.

Secondly, you need a strong source of CO2.  Your kombucha will always have active bacteria and yeast in it, but you will also need to give it a supply of sugars to “feed on” to continue creating CO2 within your bottles.  This is why most recipes recommend leaving a bit of sweetness from the first fermentation.  Alternatively, you can add fruit juice, honey, or even plain sugar syrup in the second fermentation.  The more sugar in the second fermentation, the more supply there is to create carbonation.

The final factor in creating pressure is time.  The longer you allow the fermentation process to continue, the more CO2 gas is created.  If you are not satisfied with the carbonation at 2-3 days, try leaving it for a few extra days at room temperature.  However, leaving your brew to build more CO2 pressure at room temperature is useless if the CO2 is not dissolving in to the liquid due to warm tempertatures.

In fact, it creates an undesirable effect of spilling over upon opening since the CO2 is not effectively dissolved in to the kombucha.  You can watch many Youtube videos of brewers with exploding kombucha and it a lot of fun to watch, not to clean up.  Therefore, it is important to take note of our last recommendation:

LOW TEMPERATURE

This is the key element that many recipes on the web do not account for.  As we have already learned, CO2 can dissolve more effectively in kombucha when it is in a colder environment.  However, it is also important to note that a colder temperature slows down the fermentation process in kombucha which makes it build pressure more slowly.  Therefore it is ideal to create enough CO2 pressure at room temperature as noted above, and then place it in the fridge for the CO2 to dissolve in to the kombucha.

The low temperature does not work it’s magic instantly.  You will not have the full results the moment your kombucha is cold.  It requires a few days at a minimum for the carbonation to dissolve in to your brew.

If you leave it in the fridge long enough, you can strongly reduce the chance that you have an explosion of foam when you open your bottle.  In addition, you will notice that the carbonation is harder on the tongue and enjoyable if you prefer it strong.  At times we have left our kombucha in the fridge for over a week or two to see how carbonated we could get it and were very happy with the results.

SUMMARY

Try our “carbonation recipe” and see if you get the carbonation you are looking for:

  1. Start the second fermentation while you can still detect sugar on your palate when sampling the raw kombucha (use fruit, honey or plain sugar syrup to sweeten it if there is no sweetness left)
  2. Leave bottles at room temperature in a dark place for 4-6 days (23 degrees or so, leave longer if your home is cold)
  3. Without opening the bottles, place in to fridge and leave for 4-6 days
  4. Try your kombucha!

You may still want to open the bottle carefully just in case there is still residual carbonation that is not dissolved.  Is shouldn’t spill over but everyone’s recipe, ingredients and climate is different which can alter the results.

Let us know how it works for you and always feel free to ask us more questions! Happy Brewing!

Brew Your Bucha

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