How long is the typical diacetyl rest temperature maintained?

Maintaining a diacetyl rest for 24-48 hours is a common practice in brewing, particularly for lagers. This phase typically occurs after the fermentation has peaked, and the temperature is raised slightly (by about 2-4°C) to encourage yeast activity. During this time, the yeast can metabolize diacetyl, a compound that can impart undesirable buttery flavors to the beer.

The timeframe of 24-48 hours is optimal as it allows enough time for the yeast to clean up the diacetyl without prolonging the rest beyond what is necessary. If the temperature is maintained for less than 24 hours, there may not be sufficient opportunity for the yeast to reabsorb the diacetyl effectively. Conversely, extending the rest beyond 48 hours might not significantly enhance the yeast's ability to eliminate the compound and could potentially lead to other fermentation issues or off-flavors. Hence, the practiced duration of 24-48 hours strikes a balance that maximizes the yeast's ability to improve the beer’s flavor profile while minimizing risks associated with extended diacetyl rests.