pH

pH is a scale used to measure how acidic or alkaline a liquid is, running from 0, extremely acidic, up to 14, extremely alkaline, with 7 considered neutral. In home fermentation, pH generally drops as lactic acid bacteria convert sugars into lactic acid, so tracking it over the course of a ferment gives a rough sense of how the fermentation is progressing.

Home fermenters commonly use pH strips or a digital pH meter to spot-check brine partway through a ferment, particularly for vegetable ferments like sauerkraut or pickles. Digital meters tend to give a more precise reading than strips, though both need to be calibrated or checked periodically to stay accurate, and strips can be harder to read against cloudy or colored brine.

It is worth being clear that pH is only one data point among several, alongside smell, taste, texture, and visual signs, and widely available home fermentation guidance does not treat any single reading as a guarantee of anything. Because factors like ingredient variation, temperature, and technique all affect outcomes, many resources encourage using established, tested recipes and learning to recognize normal fermentation signs rather than relying on one number in isolation.