Lesson 3 - Warm and Cold Maturation SAQ
This lesson allows you to test yourself on the material covered in the Warm and Cold Maturation lesson, and determine the level to which you have met the learning outcomes.
Suggested Response - Q2
*What are VDKs and how are they converted during the warm maturation process?
Response:
Vicinal diketones (VDKs) comprise of diacetyl and 2,3-Pentanedione which have a buttery and butterscotch flavour. This flavour is undesirable in light beers such as lagers but can contribute favourably to the flavour profile of dark ales, for example.
VDKs exist in the beer at the end of fermentation, and a typical lager fermentation will include what is called a diacetyl rest. This is a period of 24-48 hours where the beer is maintained at 14-16 °C to allow the removal of diacetyl by the yeast, to an acceptable level. Once the conversion of α acetolactate to VDKs and the subsequent reduction of VDKs has occurred, the temperature can be reduced to aid yeast sedimentation. If the vessel has been warm cropped, the bulk of the yeast will have been removed already so the onset of cooling will sediment out residual yeast. However, if yeast is cold cropped, then the bulk of the yeast will be removed after the diacetyl rest when the vessel is down to cold maturation temperature, normally 0 °C or less.