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Fermentation and pH

Fermentation and pH


You will likely read or hear in many places on this site about acid produced during fermentation. Many people wonder what that acid means for their health. Here’s a little scientific background about Fermentation and pH, what it means for your fermentation and for you.

What is pH?

pH is a measurement of how acidic or alkaline something is. The pH scale goes from 0 (very acidic) to 14 (very alkaline), with pH of 7 being considered neutral (neither acidic nor alkaline).
Importantly, the pH scale is a logarithmic scale, meaning that moving one number on the scale is actually a factor of 10. For example, a pH of 3 is 10 times more acidic than a pH of 4, and is 1,000 times more acidic than a pH of 6.

Isn’t acid dangerous?

We’ve all seen in the movies or on TV how acid will instantly burn through all kinds of things. And, some very strong acids can burn through things. But since anything below pH 7 is considered “acidic”, we have to be careful in giving that word too much meaning. Acids produced during fermentation are considered “weak” acids, and they will generally result in pH of 2.5 – 5 in the finished food.

But what about acidic foods?

Aren’t they bad for my health? There is a common health idea that has caught on in recent years, that most health problems–from cancer to cardiovascular disease–stem from an over-acidification of the body. In other words, foods that make your blood more acidic are bad for you, and foods that alkalize your blood are good for you.

While the validity of these claims is hotly debated, one thing is not: the pH of the food may have nothing to do with the pH effect in your body. As an example, one of the most alkalizing foods is lemon–which has a pH of 2! As it gets digested, the acid gets neutralized, and the minerals left behind have an alkalizing effect.

The same is true for many fermented foods – Fermentation and pH. Despite the acidity in the food itself, the digestion process will neutralize many of those acids. Many fermented foods–like kombucha, apple cider vinegar, sauerkraut and miso–are considered alkalizing foods, regardless of their external pH.

Fermentation and pH

What is the pH of fermented food? Of course, it depends on the food. Here are some common examples:

  • Yogurt: 4.5 – 4.7
  • Kombucha: 2.8 – 3.2
  • Sauerkraut: 3.0 – 4.0
  • Kefir: 4.2 – 4.6
  • Water kefir: 3.0 – 4.6
  • Kim chi: 4.4 – 4.7

It turns out that the acid is actually really important in preserving the foods during and after fermentation. For example, anything at pH 4.6 or below is considered safe from botulism. Fermentation was used for millennia to preserve foods of all types before refrigeration was possible, and you can use it today for the same reason! All because of acid.

Joel Stryker