A diacetyl reducing enzyme is most commonly known by its acronym, ALDC (Alpha-Acetolactate Decarboxylase), which prevents the formation of diacetyl in beverages like beer by converting its precursor, alpha-acetolactate, into a flavorless compound called acetoin. It is used in brewing to avoid the buttery or butterscotch off-flavors associated with diacetyl, especially in beers that experience hop creep or require extended conditioning.

How it works:

Precursor Conversion: During fermentation, yeast produces alpha-acetolactate, which can be converted to diacetyl.

Flavorless Compound: ALDC acts on alpha-acetolactate, transforming it into acetoin, a harmless and flavorless substance.

Benefits of using ALDC:

Prevents off-flavors: Eliminates the buttery or butterscotch notes diacetyl would create.

Reduces conditioning time: Accelerates the process of making beer ready for bottling or kegging by minimizing diacetyl formation.

Manages hop creep: Mitigates the unwanted formation of diacetyl that can occur when hops are added to already fermented beer.

Wide pH activity: Products like Brewzyme-D can function effectively within a broad pH range (4.0-7.0), ensuring consistent results.

When and how to use it:

Proactive application: ALDC is most effective when added at the beginning of fermentation, before significant amounts of alpha-acetolactate accumulate.

Cold-side use: Enzymes like Brewzyme-D are sterilized and safe to add after the boil on the "cold side" to prevent contamination.

During dry hopping: It can also be added during dry hopping to control diacetyl formation and hop creep.