Welcome to Part 2 of High Gravity Brewing! Read Part 1 here.
3. Brewing Process
To create wort that is more highly fermentable, mash between 140 and 149 F. This is the ideal temperature range for beta amylase, which is the enzyme responsible for breaking down starch chains into their most fermentable form. On the other hand, to create wort with higher levels of dextrines, mash in the 150-158 F range. Many brewers employ a mash at 150-152F for a more even balance of dextrines and fermentable sugars, and are still able to achieve a high abv.
Boil volume is one factor many homebrewers overlook when brewing high gravity beers. Many simply calculate water volumes for the mash and sparge like any other recipe, resulting in a boil volume of approximately 6.5gal for a 5gal batch. Nothing wrong with that, but . . .
. . . If you’ve got the equipment, consider boiling 7 or 7.5gal instead, and for as long as it takes to boil down to about 5.5gal. This method lets you collect more fermentables and dextrines from the sparge—just be careful to stop collecting wort when the gravity reaches 1.008 or a pH above 5.8. By boiling longer and condensing the wort, you’ll develop more complex aromas and flavors.
Similar to mashing, you can control temperature during fermentation to create the best conditions for yeast in a high gravity beer. Ensure that primary fermentation takes place in the temperature range specified for the yeast strain being used. For many ales, this will be around 62-74 F. Lagers will be in the 48-55 F range.
If the temperature is too cold during primary fermentation, yeast will become sluggish or, worse, dormant. In other words, fermentation may slow down or stop altogether.
If the temperature is too hot, yeast may create excessive esters and higher alcohols, resulting in a solvent-like aroma and flavor. Or, yeast may begin to die off, which can result in an incomplete fermentation and off-flavors and -aromas.
This final factor could either be the easiest or the hardest thing for a brewer to accomplish: Do nothing. Seriously, leave the beer alone once it has been transferred to the secondary fermenter. High gravity beers typically take longer to ferment completely. Moreover, age can do wonders to the flavor and aroma profiles of a high gravity beer.