Acidity. (a) The quality or state of being sour, i.e., of containing enough acidic constituents to produce a pH value (q.v.) below the neutral point of 7. (b) A condition that characterizes to varying degrees some doughs (q.v.) and baked products, as sourdough French bread (q.v.) and certain rye breads (q.v.), that are produced by methods of fermentation (q.v.) involving acid-producing bacteria of certain Lactobacillus and/or Acetobacter species, or that have been fortified by the addition of sours (q.v.) or acidulents (q.v.). (c) Its occurrence in a yeast-fermented dough is generally indicative of a fermentation that has been allowed to proceed over an extended period.