Forced Diacetyl Testing

Category : Technical
Date : June 7, 2024
Author : White Labs


Diacetyl is a common buttery off-flavor that occurs during fermentation. Alpha-acetolactate, the precursor to diacetyl, can also remain in beer after fermentation and is odorless. Once the yeast is removed from beer, this precursor is converted to diacetyl, leaving residual buttery character.

This method is a quick and easy way to ensure diacetyl and its precursor, alpha-acetolactate, have been sufficiently removed from the beer before cold crashing. A beer sample is heated to accelerate the conversion of alpha-acetolactate to diacetyl. 

If diacetyl is perceived in the test sample, there is still a significant amount of precursor that needs to be degraded and absorbed by the yeast before cold crashing. We recommend rousing the yeast as well as raising the temperature by 2 to 3 degrees. Packaging beer before validating the absence of alpha-acetolactate can result in conversion to diacetyl and perceivable amounts of buttery off-flavors in the package.

Download Forced Diacetyl Guide




  1. Heat the water bath to 140-160°F/60-71°C.
  1. Aseptically collect beer into two 50 mL conical tubes and centrifuge
  1. Move beer off sediment into a clean new 50 mL conical tube.
Note: If a centrifuge is not available, cold crash beer sample to get yeast out of solution.
  1. Place one 50 mL tube in the water bath at 140-160°F/60-71°C, while keeping the other at room temperature
  1. After 10 to 30 minutes, remove the sample from the water bath and cool to the same temperature as the other sample. An ice water bath or a cold box is effective for cooling. 
  1. Remove cap, smell and taste each sample
    1. If you smell the buttery character of diacetyl in either or both samples, let the beer condition longer. 


  • Use a diverse panel of tasters, both trained and untrained, for sensory
  • Train your sensory panel, order Diacetyl spikes from Siebel, or use things like yogurt or chardonnay to get accustomed to Diacetyl aromas.


Prevent The Formation of Diacetyl During Fermentation

Brewzyme-D is a new White Labs product that’s designed to be added on the cold side. This ALDC enzyme reduces the flavor of diacetyl and makes more consistent fermentations in shorter times. Made with Alpha Acetolactate Decarboxylase (ALDC)
  • Eliminates the risk of diacetyl formation in your beer.
  • Reduces maturation time = Faster Beer Turnaround Timelines.
  • Improves overall beer quality.

Prevent hop-creep in dry hopped beers
Add during dry-hopping to thwart secondary formation of diacetyl.

Save Time & Money
Reduce the maturation time of lager by up to two weeks.
Eliminate the risk of diacetyl formation in your beer with Brewzyme D. Adding Brewzyme D with your yeast pitch results in the decarboxylation of alpha acetolactate to acetoin. Breaking down the precursor to diacetyl during fermentation prevents diacetyl from forming, reducing maturation time and improving overall beer quality.  

Brew with Brewzyme-D