PH
A chemical shorthand for [p]otential of [H]ydrogen, used to express relative acidity or alkalinity in solution, in terms of strength rather than amount, on a logarithmic scale. Thus, a pH of 3 is 10 times more acidic than a pH of 4. See Acidity. A pH of 7 is neutral; above 7 is increasing alkalinity (referred to as alkali/alkaline or base/basic material) and below 7 is increasing acidity.
pH is an important consideration for any ferment. Most stalled fermentations are due to pH crashes below 4.
pH vs Total Acidity or Titratable Acidity (both are shortened to TA) pH is a measure of the relative number of hydrogen atoms in a solution, whereas TA is an absolute measure of how much acid is in a solution. Think of it like this: pH is how strong an acid is, whereas TA is how much of that acid is in a solution measured in volume, usually mol/liter for total acidity or grams/liter for titratable acidity. Either TA is in effect a measure of the % of the solution that is the acidic.