BB Turbo Yeast and Diacetyl Removal

Fermenting yeast produces hundreds of unique compounds that give beer its unique character, including diacetyl with its butter-like taste, considered undesirable by most brewers. Although it doesn’t pose any health hazards, diacetyl can create off-flavors in beer that is particularly problematic in certain styles such as pilsners and English ales.

Diacetyl (2,3-butanedione) is a volatile vicinal diketone produced as an end product of yeast valine metabolism during fermentation and found in some commercial and homebrewed beers, lending their distinctive buttery or butterscotch-like flavors. Furthermore, diacetyl can also be found used as synthetic butter flavoring in products like microwave popcorn, confectionery, and electronic cigarette liquids.

Diacetyl is produced during both the lag phase and exponential phase of fast fermentation due to high fermentation temperatures that favor chemical reactions between acetolactate and diacetyl. If produced too frequently in your beer, temperature control, sanitation, and proper storage techniques can reduce its concentration significantly.

Many breweries and home brewers employ a process called diacetyl rest to reduce the formation of this off-flavor in beer. This involves holding temperatures above lagering temperatures for two days prior to being cold conditioned (kept near freezing conditions). Brewers may adjust this timing depending on the yeast strain used or style of beer being created.