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Kombucha and pH: The complete guide to raising and lowering pH

pH and kombucha have a significant relationship.

The pH is an essential measurement when preparing kombucha, as it is a central indicator of whether your infusion is drinkable or not - it also reveals the taste.

By understanding what pH is and how to influence it, you'll be able to brew kombucha safely without fear of unwanted bacterial growth.

When starting the ferment, it is essential to test your pH.

We recommend aiming for 3, with 2.5 - 4.2 being considered a safe range.

The low pH levels kill harmful bacteria while keeping healthy bacteria and SCOBY alive.

This allows us to obtain all the probiotic nutrients without any danger.

Higher pH levels could become a breeding ground for unwanted growth.

Ensuring that the brewing environment is within this safe range ensures that no disease develops and contaminates your batch.

What is pH?

[Definition]

"The pH value of a drink is a direct function of the free hydrogen ions present in the drink".

In simple terms, any liquid contains a certain number of free ions, which you can think of as particles.

The more free ions there are in a liquid, the more acidic it is.

The more acidic it is, the lower the number on the pH scale.

For example, vinegar contains a lot of free ions, so it is more acidic and has a pH of 2.4.

The scale on which they are measured is logarithmic, meaning that the closer you get to 1, the more extreme the pH, and the closer you get to 14, the more extreme the pH.

If you don't quite understand this point, don't worry, it's not necessary to make excellent kombucha!

pH in perspective

To show how the pH of kombucha compares with that of other common drinks, we've created a table showing the relative values.

Most of the beverages we consume are within the range indicated for our consumption.

Drink
              pH value 
Your Kombucha brew
               2.5 – 4.2
Coca
               2.52
Water
               7
Vinegar
               2
Milk
              6.5
Breakfast Tea
              6.3
Starbuck café
              6

Ingredients and their influence on pH

Each ingredient in kombucha has an impact on the pH.

To obtain the right pH, it is necessary to know the influence and impact of each ingredient individually on the pH of the batch.

                         Ingredient
              Effect on pH
          Kombucha Starter Tea
               Decreases
                          SCOBY
               Decreases
                         Water
               No change
                         Sugar
               No change
                         Honey
               Decreases
                         Tea
               Decreases

Starter tea for kombucha - This tea comes from a previous batch of fermented kombucha tea.

The pH will therefore be at the same level as that of kombucha tea, i.e. about 2.5 to 4.

When added to a new batch of kombucha, it lowers the pH of the batch.

SCOBY - A SCOBY is a large culture filled with bacteria.

As SCOBY is usually stored in a SCOBY hotel or transported in starter tea, it becomes impregnated with the kombucha liquid.

Like the starter tea, it will probably lower the pH of the new batch.

Water - Most recipes for new batches recommend using filtered, non-chlorinated water.

Pure water has a pH of between 6.5 and 8, generally 7 - in other words, it is neutral.

The pH of other ingredients will easily influence a neutral pH.

Sugar - The sugar is poured in solid form and then dissolved in the tea.

Whether in solid form or dissolved in a liquid, it does not alter the pH.

There is therefore no impact: the pH before and after the addition will remain the same.

Honey - If you're making Jun or other flavours of kombucha, you need to know the pH of the honey.

On average, it is between 3.4 and 6.1.

Slightly on the acid side of the spectrum.

Tea - This will depend on the type of tea you use to brew your batch.

Green tea has a relatively high pH (7-10), while black tea has a much lower pH (4.9-5.5).

Testing the pH of kombucha

pH - Digital metre or litmus paper: Points to consider when buying

There are many methods of measuring pH, each with its own advantages and disadvantages.

Below is a list of points to consider before buying a pH tester.

Accuracy - The number one factor to consider is accuracy.

For the old universal indicator paper, accuracy can be difficult to determine.

They are highly dependent on the colour of the paper, so if there is a discrepancy between the figures or if the lighting changes, it is difficult to know which is the correct reading.

When choosing a measuring device, look first for accuracy - has it been tested? Can it measure to within 0.1 %?

These are some of the questions you need to ask.

Awards - The reason why litmus paper and other styles of analogue tests are still so popular is the very low price.

Some companies even offer 100 tests for less than 3€.

A digital version cannot compete on price.

Brand - There are no big names producing testers.

So, in terms of brand, there's not a lot of loyalty. If we were to recommend a digital player, we'd look for a product under £30 that has good ratings online.

Size - Some of the fancy reading kits can be quite large.

But it's important to remember that it has to fit into the mouth of the pot you're trying to test.

When making your choice, think about the size of the device and whether it will fit into the neck of the most common jars you will be using.

Test the pH of the kombucha with an electronic reader.

A pH tester is 100% necessary when brewing kombucha, an electrical meter is probably the simplest and most accurate method of measurement.

They will often have a probe or pointed edge that you can place inside the liquid.

1. Make sure your brew has been stirred (stir very gently once).
2. Following the instructions on your device, switch on your player and make sure it is ready.
3. Place the measuring end inside the jar (set the SCOBY aside if necessary).
4. Press the measurement button on your device
5. Read the pH reading

If you are satisfied with the corresponding pH, you can proceed to the next section.

If not, see the section below on how to reduce the pH of your kombucha.

Testing the pH of kombucha with test strips

Do I need pH strips for kombucha?

If you make kombucha using an all-in-one kit often, they will add litmus paper which will contain about 100 strips and colours with the corresponding pH for you to judge.

1. Make sure your brew has been stirred (stir very gently once).
2. Remove a piece of litmus paper from the packaging.

3. Place a piece of paper inside the jar to reach the infusion (you may need to lift or move the SCOBY).

4. Remove the paper from the jar

5. Stand in a bright environment, hold the paper up to the light and use the sunflower packet to determine the pH of your beer.

6. If you are satisfied with the pH, you can leave the brewing on.

If this is not the case, see the section below on how to lower the pH of your infusion.

pH analysis strips

Keeping your batch within the critical pH range is not only necessary to obtain a delicious-tasting beer, but also to ensure that it is fit for human consumption.

pH and stirring guide

Brewing

Once the ingredients are in the brewing vessel, check the pH.

Make sure you stir the mixture lightly.

This way, when you perform the test, you don't accidentally test an area or an ingredient.

Instead, you get the pH of the whole container.

The test result we are looking for is a pH between 2.5 and 4.2.

This is the "safety range".

As some pH testers are inaccurate, we often recommend that you carry out several tests in different parts of the container to be on the safe side.

What should I do if my pH is too high?

If the pH of your brew is too high, this should be corrected before you start brewing.

A high pH will not create an environment that inhibits bacteria and their growth, which could be very dangerous for your health.

Here are two ways to lower the pH of your infusion.

Method 1: Add organic white vinegar to your brew

1. Add 1 tablespoon of white vinegar
2. Stir slowly to ensure that the infusion is well mixed.
3. Re-test the pH to see if it is below the critical threshold of 4.2 and above 2.5.
4. If the pH is below 4.5, it is safe to start brewing.
5. Above 4.5, you need to repeat the process of adding vinegar until the pH is below this level.

Method 2: Add Kombucha tea to your brew

1. Add half a bottle of your favourite kombucha (8oz or 250ml is usually enough).
2. Stir gently, so that the mixture is homogeneous.
3. Re-test the pH to see if it is below the critical threshold of 4.2 and above 2.5.
4. If it is within this critical range, you can start brewing.
5. If the pH is still too high, add kombucha tea and repeat the operation until the pH reaches this value.

White vinegar

Organic white vinegar will not alter the taste of your infusion too much, but it will reduce the pH.

If the pH of your brew is too high, even after adding your tea starter, you will need to add organic white vinegar to reduce it.

Can the pH of kombucha be too low?

Yes, absolutely! Although not as common a problem, the pH of kombucha can be too low.

The figure generally quoted is that anything below 2.5 is too low.

This can be tested using the same methods as above.

If the pH is below 2.5, the acidic nature can be harmful to your health.

Under no circumstances should you drink anything so acidic.

To increase the pH, you will need to dilute the existing batch.

One method is to add filtered, non-chlorinated water.

Another way of avoiding wasting beer would be to use this batch as a starter liquid for another batch.

Secondary fermentation and pH

Secondary fermentation and pH are not as important.

It is generally in the range of 2.5 to 3.5.

Many commercial brewers will, at this stage, pasteurise the brew, killing any chance of bacterial growth.

The main reason why pH is so crucial during brewing is to stop the growth of bacteria.

So if it has been pasteurised, all the dangerous bacteria have been killed off.

As a home brewer, I would check the pH to make sure that the final batch.

Between 2.5 and 3.5, you can bottle and get ready to flavour!

If you go ahead and pasteurise your homemade kombucha, I'd still check the pH, but I'm sure that if you follow the correct pasteurisation process, the bacteria will be killed.

How often should the pH be tested during brewing? 

Test the pH after making the load, to make sure it is between 2.5 and 4.2.

Then check daily to make sure the environment hasn't changed and that the infusion will still be safe to drink when it's ready.

pH by type of kombucha infusion

The pH of an infusion directly influences the taste of the finished kombucha.

The main way to see this is by the level of smoothness of the finished product.

As a general rule, the higher the pH, the sweeter the infusion.

As a general rule, the longer you let kombucha steep, the more acidic it becomes.

So when you're nearing the end of the brewing time, you need to check the pH to make sure it's within the critical range.

If you're looking for a sweet elixir, aim for a slightly higher pH, around 3.5, but make sure it stays within the safe range.