When fermenting what causes souring?!
When fermenting what causes souring?
Answers:
Infection by an acid-producing bacteria. These usually produce either acetic acid (acetobacter) or lactic acid. Other bacteria and wild yeasts can produce a range of other off-flavours.
With some styles of beer, e.g. some of the Belgian ones, such infection is desirable since it produces flavours that are a characteristic of the style.