temperatures, or exposure to the air, all
conditions that favor the growth of
undesirable microbes. In particular, if the
vegetables are not weighted down to keep
them below the brine surface, or if the brine
surface is itself not tightly covered, a film of
yeasts, molds, and air-requiring bacteria will
form, lower the brine acidity by consuming its
lactic acid, and encourage the growth of
spoilage microbes. The results may include
discoloration, softening, and rotten smells
from the breakdown of fats and proteins. Even
the helpful Lactobacillus plantarum can
generate an undesirably harsh acidity if the
fermentation is too vigorous or prolonged.
Unfermented, Directly Acidified Pickles
There are also a host of fruit and vegetable
products that are pickled not by fermentation,
but by the direct addition of acid in the form
of wine or vinegar, which inhibits the growth
of spoilage microbes. This ancient technique