What is ALDC in beer?

Answered by Paul Bowser

ALDC, also known as alpha acetolactate decarboxylase, is an enzyme that can be a great ally in the process. Its main function is to limit the production of diacetyl, which is a compound that can result in off-flavors in if present in high amounts. By adding ALDC either at pitching or during dry hopping, brewers can protect their finished beer from these off-flavors and reduce the conditioning time required before the beer is ready to be bottled or kegged.

Diacetyl is a compound that has a buttery or butterscotch-like flavor and aroma. While some beer styles, like certain lagers and English ales, may benefit from a subtle presence of diacetyl, excessive amounts can be perceived as a flaw and negatively impact the overall drinking experience. It can give the beer a slick or oily mouthfeel and an unpleasant aftertaste.

ALDC works by converting acetolactate, a precursor to diacetyl, into acetoin, which has a much milder flavor profile. This conversion occurs through the process of decarboxylation, where a carboxyl group is removed from the molecule. By reducing the amount of acetolactate available, ALDC effectively limits the formation of diacetyl during fermentation.

The addition of ALDC can be particularly beneficial in beers where the yeast may not naturally produce enough of the enzyme to fully convert acetolactate. This is often the case with certain strains or when using high-gravity worts. By introducing ALDC, brewers have more control over the diacetyl levels in their beer and can ensure a cleaner, more consistent flavor profile.

To use ALDC, it is typically added to the wort or beer along with the yeast at the beginning of fermentation or during dry hopping. The enzyme works best at temperatures between 18-25°C (64-77°F) and at a pH range of 5.0-6.5. It is important to follow the manufacturer's instructions for dosage and timing, as the optimal conditions may vary depending on the specific ALDC product being used.

In my personal experience as a brewer, the addition of ALDC has been a game-changer in certain beer styles. I have found it particularly useful when brewing hop-forward beers, such as IPAs or pale ales, where hop flavors and aromas can sometimes mask or accentuate off-flavors like diacetyl. By using ALDC, I have been able to ensure a cleaner and more balanced beer, with a quicker turnaround time from fermentation to packaging.

ALDC is an enzyme that can be added to beer during fermentation or dry hopping to limit the production of diacetyl. By converting acetolactate into acetoin, ALDC helps to reduce the presence of diacetyl, resulting in a cleaner and more enjoyable drinking experience. Brewers can benefit from using ALDC, especially in styles where diacetyl is considered a flaw or when aiming for a quicker conditioning time.