Imperial Stout - Double Mash!
High ABV Stouts have been around forever. In fact, Stout was originally used as an adjective to describe a beer that was higher in alcohol content. A Stout Amber for example, or a Stout Porter. In time Stout became it’s own classification as a dark beer, and in American craft beer, it has taken on yet another adaptation to simply be “aggressive dark beer”. Imperial Stout takes it up a notch further and usually comes in above 10% ABV.
The BEERMKR Imperial Stout is a huge beer, coming in at 10.5% ABV with an all-grain mash. In the machine we achieve this with process called “double mashing”, which is exactly what it sounds like. We run the brew cycle twice with two sets of grain to extract even more sugar.
This Imperial Stout is all about the grains. A huge amount of 2-Row gets the fermentable sugar content into high gravity range. Biscuit malt brings a nice toasted, nutty flavor profile that is similar to baked goods. Melanoidin malt provides a hearty amount of, you guessed it, melanoidins! This malt is often used as a substitute for decoction mashing where the wort is removed from the grains and boiled separately to concentrate sugar and produce malliard reactions. Malliard reactions are responsible for the browning of bread crust in the oven, and the browning of sugar when creating caramel.
So far in the grain profile we have light fermentable sugar from the two-row, baked goods profile from the Biscuit malt, and complex browned sugar profile from the Melanoidin malt. To make it a Stout, we need to add some dark grains. To accomplish this, we are using both Black Malt and Roasted Barley. Black Malt is malted barley, like 2-Row, that has been kilned at high temperatures until it’s very dark. Doing this to malted barley provides a more neutral, clean flavor profile. Roasting unmalted barley results in a bit more astringency which can dry out the flavor profile, and that is exactly what Roasted Barley is. Using both Roasted Barley and Black Malt allow us to balance the dark flavor profile and dial in how aggressive we want the dark grain profile to be.
Bitterness and Balance
We don’t have many hops in this beer, just a single 60-minute addition of Magnum to bring the bitterness to a respectable 62 IBU. The resulting bittering units to gravity units (BU:GU) ratio is 0.56. This is computed by dividing 62 IBUs by the original gravity after moving the decimal to the right two places (1.103 starting gravity = 110.3 gravity units). This ratio gives the brewer guidance on how balanced the beer will be. For comparison, Light Lagers have a BU:GU ratio of 0.30 (not very bitter), IPAs are between 1.0 and 1.2 (very bitter), German Pils is around 0.6 (moderately bitter). What this calculation doesn’t do is factor in the bitterness derived from the dark malts, which is unfortunately not easily calculated and must be measured by a laboratory spectrophotometer. When doing so, this beer will come out closer to 0.8 in its BU:GU ratio.
This beer is fermented with an English derived S-04 yeast. S-04 is a very clean yeast with tart fruit esters that come together nicely in a beer this big. In every mash, there will be some portion of sugars produced that will not be fermentable by saccharomyces cerevisiae, or standard brewers yeast. The more grain we mash, the more of these non-fermentable sugars end up in your beer. Couple that with yeast becoming less efficient as the alcohol increases, and the end result is more sugar left over with higher gravity beers. This is expected in all high gravity styles and is the case here as well. This left over sugar provides a great body and mouth feel to counteract some of the boozy notes that inevitably happen with 10%+ ABV beers.
All this flavor and ABV development takes time to achieve. Your BEERMKR will perfectly maintain the fermentation temperature of the beer and prevent any off flavors from developing. The primary fermentation and rest will wrap up in 11 days, and we recommend cold conditioning this monster for another week before pouring a glass. After 3 weeks in the tap, the layered complexity of this beer will become apparent. If ever there were a BEERMKR beer to bottle and cellar for a year or two, this would be it!