During the fermentation of milk with lactobacilli, the pH is typically in the
range of 3.9 to 4.4. Thus, in some cases, it is the acidity of the final fermentate that
can prove inhibitory to lactobacilli when cultured in milk-based media, whereas it
does not affect the survival of the aciduric or acid-tolerant species of lactobacilli.
At this point, fermentation is usually stopped by cooling and/or neutralization, which
will prevent acid during subsequent processing or storage.