ALDC in Brewing: A Practical Guide for the Home Brewer

ALDC (Alpha Acetolactate Decarboxylase) is a brewing enzyme that has quietly become a staple in modern commercial breweries, particularly those pushing hop-forward styles or tight production schedules. For home brewers, ALDC can feel a little mysterious – but used correctly, it can be a powerful tool for improving flavour stability and reducing the risk of unwanted buttery notes.

What Is ALDC?

ALDC is an enzyme that works by converting alpha-acetolactate directly into acetoin, bypassing the normal pathway that produces diacetyl. Diacetyl is responsible for buttery or butterscotch flavours, which are generally considered a fault in most beer styles.

In simple terms: ALDC prevents diacetyl from forming in the first place, rather than relying on yeast to clean it up later.

The Diacetyl formation pathway

Why Diacetyl Matters (Especially in Hoppy Beers)

Diacetyl can creep into beer for several reasons: stressed yeast, under-pitching, rapid cooling, or heavy dry hopping. Dry hopping in particular can reintroduce alpha-acetolactate into the beer, leading to what’s often called ‘hop creep’. Hop creep can restart fermentation slightly, increasing diacetyl levels after you thought fermentation was complete. This is why some heavily dry-hopped beers can develop a buttery edge days or weeks after packaging.

Benefits of Using ALDC

- Reduces the risk of diacetyl and butterscotch flavours

- Particularly effective in dry-hopped and hop-forward beers

- Can shorten conditioning time by reducing diacetyl rest requirements

- Improves flavour consistency from batch to batch

- Useful insurance when fermenting cool or under pressure

With ALDC vs without ALDC

When to Add ALDC

ALDC is typically added at the start of fermentation. For most home brewers, this means adding it directly to the fermenter at the same time as yeast pitching. Adding ALDC early allows it to act on alpha-acetolactate as it is produced, preventing diacetyl formation throughout fermentation. In some commercial setups, ALDC can also be added during wort transfer or inline, but for home brewing, fermenter addition is the simplest and most reliable method.

How Much ALDC to Use

ALDC is used in very small quantities. Always follow the manufacturer’s dosage guidelines, as products can vary in concentration. As a general rule, ALDC is measured in millilitres per hectolitre, meaning home brewers will often be adding just fractions of a millilitre per batch. Accurate measurement is important – using a syringe or pipette is strongly recommended.

[IMAGE PLACEHOLDER – Syringe measuring small liquid addition]

Does ALDC Replace a Diacetyl Rest?

ALDC significantly reduces the need for a traditional diacetyl rest, but it doesn’t completely replace good fermentation practice. Healthy yeast, correct pitching rates, oxygenation, and temperature control still matter. Think of ALDC as a safety net rather than a shortcut.

Which Beer Styles Benefit Most?

- New England IPA (NEIPA)- American IPA and Pale Ale- Cold-fermented lagers- Beers fermented under pressure- Any beer with heavy or late dry hopping

Things ALDC Does NOT Do

- It does not remove diacetyl once it is already present

- It does not fix poor yeast health

- It does not prevent oxidation or infection.

ALDC works best as part of a well-managed brewing process.

Final Thoughts

For home brewers looking to tighten up their process and produce cleaner, more stable beer – especially in hop-forward styles – ALDC is a simple and effective tool. Used correctly, it can reduce risk, save time, and help ensure that the beer you package tastes exactly how you intended. Buy your ALDC in 1ml shots or 10ml bottles here.