Acetolactate decarboxylases

Enzymes, catalogued as EC 4.1.1.5, that convert alpha-acetolactate directly into acetoin, short-circuiting the pathway that would otherwise generate diacetyl. Brewers prize this reaction because diacetyl’s buttery note is an off-flavour in most beers, forcing long maturation while yeast slowly reabsorbs it; adding acetolactate decarboxylase clears the precursor quickly and shortens tank time. The same enzymes serve analysts measuring diacetyl and acetoin during brewing. It is a neat example of single-enzyme problem-solving in food processing: redirect one metabolic branch and a flavour defect disappears.