How to Measure pH in Fermentation (And When Not to Rely on It)

How to Measure pH in Fermentation (And When Not to Rely on It)

Introduction & Product link

These are the pH strips Matt uses link: https://amzn.to/4n6Z1gm
If you’re a fan of fermentation like Matt, then pH strips should be a staple in your kitchen. The measuring of acidity can of course tell you when your ferment is done, but it can also give you clues as to it’s microbial population and where the microbes may be in their life cycle. Getting pH right can make a big difference in the success of your ferment which is why Matt has incorporated it in his home fermentation kitchen.

What is pH and Why Does It Matter?
pH is a measure of how acidic or alkaline something is, on a scale from 0 to 14. In fermentation, a dropping pH tells us that beneficial microbes like lactic acid bacteria are turning sugars into acid.

For example, a yogurt lactic acid bacteria will eat lactose, that lactose will go through the bacteria digestive system and out the other end will come lactic acid. That is how ferments get their acidity. Also, microbes that are eating are microbes that are reproducing. If you are getting more acid that means the bacteria are multiplying and your CFU units are going up.

For most ferments, a lower pH means a safer, more stable environment. For example:

• Yogurt is typically finished around pH 4.2 to 4.5

• Sauerkraut often settles between 3.2 to 3.8

• Most fermented foods are considered shelf-stable or safe under pH 4.6

How to Measure pH at Home
There are two main tools you can use:

1. pH Strips

   • Affordable and easy to use

   • Choose strips that have at least a 0.5 increment

   • Ideal for liquids like whey, kombucha, or brine and semi liquids like yogurt.

   • Simply dip or dab a clean sample onto the strip, then compare colors

2. Digital pH Meters

   • More precise (readings to 0.01)

   • Requires calibration and proper cleaning

   • Ideal for frequent fermenters or thick samples like yogurt

What Your pH Reading Actually Tells You

• A dropping pH = microbial activity is underway

• Target zones help you decide when to stop fermentation

• pH can also hint at flavor (tangier = lower pH)

• If pH drops too low, some probiotics may begin to die off (especially below 4.0 in yogurt)

When pH doesn’t help
While pH can be very helpful, it has limitations. Here’s when it may not give you the full picture:

1. Thick or Uneven Ferments

   • Yogurt or coconut yogurt may show different pH in the whey vs. the curd.

   • Always sample evenly or test the whey for accuracy.

2. Low pH, But Still Sweet

   • In some soda or fruit ferments, the pH might be low even though fermentation is incomplete.

3. Over-Fermentation

   • A low pH doesn’t mean high probiotic count forever. Once microbes acidify their environment too much, they begin to decline. This is called auto-inhibition.

4. Different Acid Profiles

   • Kombucha and vinegar-based ferments involve acetic and gluconic acids, not just lactic acid. pH alone can’t tell you which microbes are thriving.

What To Use Alongside pH
To get a full picture of fermentation, pair pH testing with:

• Time (track fermentation days)

• Taste and smell (sharp, clean, and sour = good)

• Texture changes (separation, bubbles, or fizz)

• Temperature control (faster fermentation at warmer temps)

If you want to track your ferment pH over time, download Matt's free fermentation logbook to start logging your results.

Happy fermenting!