The Brülosophy Podcast Episode 398 | Impact ALDC Has On A Festbier
Sep 30, 2025
Join Jordan Foulkes, a fermentation expert and homebrewer, as he dives into the fascinating world of diacetyl control in brewing. He explains diacetyl's sensory impact and how it forms, detailing methods to mitigate it. The discussion covers the benefits of using alpha-acetolactate decarboxylase (ALDC) as an insurance policy against diacetyl in Festbier, alongside practical brewing techniques. Tune in for intriguing results from triangle tests that shed light on how effective ALDC can be in ensuring clean flavors.
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What Diacetyl Is And Why It Matters
- Diacetyl is a common VDK producing buttery, popcorn-like flavors and a slick mouthfeel in beer.
- Small amounts can suit some styles but most brewers view it as an off-flavor to avoid.
Diacetyl Forms From AAL Plus Oxygen
- Yeast produces alpha-acetolactate (AAL) while making valine and some leaks into beer as a diacetyl precursor.
- Oxygen exposure converts AAL into diacetyl, so cold-side oxygen control is crucial.
Prevent Diacetyl By Prioritizing Yeast Health
- Pitch healthy, abundant yeast and provide good nutrients to reduce diacetyl risk during fermentation.
- If fermenting cool, consider heavier pitching or a diacetyl rest to help yeast reabsorb off-flavors.