You’re staring at it… you’ve picked it up and smelled it, placed it against the light, imagined what the first sip will taste like…
All you know is that a mix of flavors from fruity notes to a nice hop bouquet will leave some sort of palate feeling in your mouth… you know that everytime you drink a beer with dark malts on it, the acidity will sharpen up your taste buds…
Just then, you taste the beer and realize that the beer is not sharp, but well rounded…
That is the power of diacetyl… a nice smooth butterscotch flavor well suited for some dark beers…
In pale lager beers it’s frowned upon… but in some dark or English bitters, that unwanted flavor in beer is wanted…
Too much diacetyl will ruin beers of all colors however… so how do you control the butterscotch flavor to keep it from your prized clean pale beers and add just enough to some of your darker beers…
If you understand how diacetyl gets into your beer to begin with, you’ll be able to control just how much of it you want if any at all…
If you don’t understand diacetyl, then you’ll see it pop out of nowhere in beers where you want a nice clean, crisp feel…
First off, diacetyl is a byproduct of yeast during fermentation… it is created regardless…
The first way to control it is by choosing the right yeast strain… some yeast strains are known to produce more diacetyl than others….
Some yeast strains are known for being clean yeast strains… but these ‘clean’ yeast strains often refer to fruity esters, not so much diacetyl… so you’ll see some yeast strains used to brew clean beers will produce high levels of diacetyl…
and that’s where temperature control comes into play…
Diacetyl will be produced during fermentation and will be reduced towards the end of fermentation depending on temperature…
The way to reduce diacetly in beer is to raise the temperature of your fermentor up towards the 65 – 70 F range, including lager yeast strains…
This is done towards the end of fermentation and preferrably done in the primary…
Low temperatures keep active yeast from absorbing diacetyl, which is the problem we run into when brewing pale lagers using diacetyl-producing yeast strains… which is the reason why a diacetyl rest around 65 F towards the end of fermentation is recommended with these brews…
So if you are brewing a darker beer and want slight levels of diacetyl, keep your fermentation temperatures below 65 and perhaps rack to a secondary as soon as fermenation is complete…
It’s reasons like this that you want to be able to control the temperature of your fermentation…
And if you want to learn more cool things you can do with temperature control, be sure to check out Better Home Brew Formula…
Cheers,
