Testing for Diacetyl

Ensure no diacetyl left in beer before cooling fermented beer (if you indeed do that). To do this, put a small beer sample in a sealable jar. Immerse jar in 170 °F (77 °C) water bath until sample is 170 °F (77 °C), holding for 15 minutes. Cool jar to room temperature in a cool water bath, then smell sample. If you detect any buttery notes, continue to age beer at room temperature and check again the next day. Cool beer once diacetyl is not detected.