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What is optimal pH value of fermented beverages?

The pH value is one of the most significant measurements used to indicate the progress of the fermentation process. It detects the presence of specific chemical factors that affect growth, metabolism, and final product.

The pH scale is a measurement of the total acidity or alkalinity of a substance. When pH scale measures from 0 to 14.0. pH 7.0 means the substance is neutral. The pH of less than 7.0 (from 0 to 6.9) is an indicator of acidity, on the other hand, any substance that has a pH of more than 7.0 (from 7.1 to 14.0) is considered alkaline.

When you are testing the pH value in your ferment, always drip the content on the strips. Don’t dip the tester into the liquid. This may give you false result!

pH value in fermented beverages


The control of pH is very important in milk fermentation since it influences not only the growth of LAB, but also their metabolic activity. Milk has a pH of 6.6, which is ideal for the growth of several microorganisms. Fermentative process of LAB causes a decrease of the pH in the milk medium, as a result of producing lactic acid. The pH of finished milk kefir after 24 hours of fermentation should be between 4.0 and 4.5. If it is higher, you should leave it to ferment for another 12 hours. It has to drop below 4.6 to prevent the possibility of the presence of pathogens. When it is below this value it is up to you when you will stop the fermentation, depending on the taste you like.

ph value in kefir
Milk Kefir has pH value under 5 which gives it a slightly sour taste.

pH of milk kefir should be under 4.6


Similar to milk kefir, pH has a significant role with growth and metabolism of microorganisms present in water kefir grains. Starting pH of water kefir solution is 6.0-5.0. After 48 hours of fermentation, it drops to 4.5-4.0. When the first fermentation is completed, water kefir has a mild sweet and a bit of tart taste with a bit of bubbles. If you second ferment it for another 12-24 hours, it will increase in carbonation and the sugar content will decrease. pH value would drop to 3.5 after 72 hours of fermentation and would get a strong, tart, sour and yeasty taste. It is recommended that you taste it frequently to find out when it is best for you. Same as with milk kefir it is considered that the pH must be lower than 4.6 to be safe to consume.

Water kefir pH value can be: 3.5-4.5


Although pH value won’t tell us the exact time when our kombucha is ready, it will tell us when it is safe to drink. Low pH prevents harmful organisms and mold from developing. Most pathogens won’t survive in a low pH environment. Starting pH of the kombucha batch must be at or under 4.5. If it is higher, you should add more starter liquid. The value of pH drops most noticeable in the first few days. It should fall under 4 to be considered safe to consume. However, at this value, the kombucha will still be quite sweet.

Take the next measurement within the first 7 days. pH should be 4 – 3,5. Dropped pH is a good indicator of the successful course of fermentation. Usually it takes 10-21 days for kombucha to ferment. pH of finished brew is from 3,5 – 2,5, based on your taste preference. When it is below 3 it will have quite strong, tart and vinegary taste. After 7 days, taste it daily to find the perfect flavour for you.

Kombucha varies from 2.5 to 3.5

pH value
Using the pH scale you can determine the current pH value in your ferment.

Knowing what the pH value of your ferment is can be a useful information. This way you can always check if your fermentation is on the right track.

Get pH tester strips here:

ph value scaling

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