As home brewers, we do a lot of things because a book told us to. The folks at the homebrew shop said so. The drunken guy we brewed with that one time did it that way. Fortunately, these explanations are often enough to get us safely through a brew day and into the fermenters. Sometimes it’s nice to know the why behind what we, as brewers, are doing. The scientific explanation behind mashing is a good ‘why’ to know.

The harsh truth of brewing is that none of us, from the first-time extract brewer to the folks behind your favorite malty beverage, actually make beer. We make sugar water, or wort, add the yeast, and hope they get along well. In order to ensure the most hospitable environment for the yeast, we can add certain chemicals, adjust times and temperatures, and do our best to keep other beer-drinking mini-flora and fauna at bay.
Mashing is a crucial step in the all-grain brewing process which contributes significantly to making yeast happy.

When we mash, we are using a combination of moisture, time, and temperature to activate certain enzymes (special proteins) in the malt (grain) that work to break down sugars, proteins, minerals, and even some fats. These enzymes work best at a variety of temperatures and pH levels, so we adjust our mash schedule according to the beer we’re making. If we wanted to make a traditional German style Oktoberfest, we might consider a protein rest around 124 degrees F. This lower temperature rest ensures the breakdown of proteins into amino acids the yeast can use during fermentation. For a dry, bitter IPA or double IPA, we want to ensure that most of the sugar from the malt is easily digested by the yeast. We mash at a lower temperature, usually between 147 and 150 degrees F, to ensure that the enzyme β-amylase has time to do its job and break starches down into maltose.

If we’re making a big stout and want some residual sweetness and a fuller body, we typically mash between 154 and 157 F. This higher temperature favors α-amylase, an enzyme that produces some maltose, but also unfermentable dextrins. Finally, we mash out around 167 F. This high final temperature starts to deactivate the enzymes we’ve been using, drops the viscosity of the wort, and makes it easier for us to run our wort into the boil kettle.

Next time you’re making your favorite Pliny the Younger clone, or a crazy experimental recipe with yard hops and bananas, remember the why behind mashing. The steps we follow during the brew day are important because we aren’t really making beer. We’re doing the best we can to make a few billion hungry little microbes happy.

As the weather cools, start thinking about your brewing plans for the Fall. Homebrewed beer always goes well at tailgate parties, Thanksgiving, or as a Christmas gift. Plan ahead, make time to brew, and as always, let us know if you have any questions about recipe creation, your next equipment upgrade, or just want to share some tasty suds.