Step Mash Your Way to a Dry Finish

So it’s warm out, and you’re itching to brew a summer beer with a super-dry finish that begs for another refill? Instead of bumping up the simple sugar adjuncts in the recipe, try a step mash.

Taylor Caron Aug 17, 2016 - 8 min read

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One of the main reasons a lot of homebrewers make the leap from extract to all-grain brewing is to have more control over the wort sugar profile. When we begin making our own wort, there are a handful of grain-native enzymes we can manipulate to influence the finished beer, but with today’s modern malts, we can put most of our attention on the “saccharifying” enzymes, alpha and beta amylase.

These two enzymes break down (hydrolyze) our grist’s amylopectin and amylose starches into smaller and more fermentable sugars, but they work in different ways. Alpha amylase cleaves these long starch chains somewhat indiscriminately into randomly smaller carbohydrates and is happiest in the 160–168°F (71–76°C) range. Beta amylase can work on only one end of the starch chain, prefers a temperature of 140–150°F (60–66°C), and falls apart (denatures) well before alpha amylase’s preferred temperature range. With a much more limited location of activity, beta amylase also works much more slowly than its alpha sibling. Luckily, there is enough overlap in the working ranges that we can expect good results by mashing in the 148–154°F (64–68°C) range, with the lower end giving us a bit more fermentable sugars than the higher end.

Let’s say that it’s brew day, and you’ve got your alpha amylase chopping those long starch chains up willy-nilly and your beta amylase nibbling the ends into fermentable sugars, working happily together at the low end of the normal mash range (148°F/64°C), and maybe you’re planning an extra twenty minutes of rest to make sure the job is complete. Great! You will definitely make beer, and it will likely be quite fermentable with a low finishing gravity, but there is more you can do!

If you really want to maximize the fermentability of your wort, you need a multistep temperature mash (step mash, for short). I’m sure you’ve heard of it, but maybe you haven’t quite mustered the courage to dive in. I am here to tell you it isn’t hard, and you might even have a bit of fun with it.


Step Mash in Practice

If you happen to have a direct-fire mash tun, to perform a step mash, you can simply dough in on the low end of beta amylase activity (138°F/59°C), let it rest for 20 or 30 minutes, then slowly (as in 2°F/1°C a minute!) add heat until you get to the 150–152°F (66–67°C) range for another 20 minutes, then again heat up through the high end of alpha amylase activity (168°F/76°C). This sort of mash profile has proven to make very fermentable wort, but it requires almost constant stirring to prevent scorching and to give the enzymes a more consistent temperature throughout the mash tun.

If, like most of us, you are using an insulated cooler as your mash tun, you’ll need to use infusions of near-boiling water to heat the mash through the steps, but the effects are comparable (and you don’t need to worry about scorching). The first step of the mash should be somewhere in the low 140s Fahrenheit (low 60s Celsius) to favor beta amylase activity, but you’ll need to dough in much thicker than you might normally to allow room for more hot-water infusions on your way up the thermometer. This is actually not a problem because, as it happens, beta amylase works better in a thick mash than a thin one (just another of the many ways Mother Nature smiles on brewers).

You should be able to dough in at around 148°F (64°C) using a 0.9:1 liquor-to-grist ratio (0.9 quarts/852 ml) of water to 1 pound/454 g of grain) and then be able to add near-boiling water (in the 1.5:1 range) to get into the mid-to-high 150s Fahrenheit (low 70s Celsius). Such a mash profile allows time for the beta amylase to do the bulk of its work well before hitting temperatures that cause it to denature. At the same time, alpha amylase is somewhat active chopping those long chains up and giving the beta more nibbly ends to work on.

The exact temperature rest points along this range are up to the brewer, so long as you understand that at the lower end, the beta is doing all of the work with no help from alpha, and at the higher end, the alpha runs solo, with beta being quickly denatured and useless. You may choose to make many small steps up through the range, adding as little as a quart (946 ml) of boiling water every five minutes over a half-hour after the initial low-end rest of 20 to 30 minutes. Or you may choose to simply jump up from 148°F (64°C) to 156°F (69°C) in one go, or anything in between.

Just remember that it’s the time spent in the middle that allows the alpha to chomp open those long starches to give beta access to more of the “reducing” end of the chain, which gives you that simple maltose sugar that yeast loves. Also keep in mind that beta amylase is both slower to work and slower to denature, so don’t fret a long initial rest on the low end. Whatever you do, take notes so that when it comes out perfect, you’ll be able to reproduce the beer!


A Few More Considerations

Now that we’ve gone over the basics of how our friends the amylase enzymes work, you are ready to pull out all the stops on the driest beer you can manage. But hold on. There are a few things to consider beyond mash temperatures and rest times.

Especially when you’re trying to finesse the dance between beta and alpha, timing can be a major factor in your success or lack thereof. To ensure that the enzymes have full access to all of those starchy bits in the grist, it’s not a bad idea to hydrate the mash for ten minutes or so before doughing in. Technically this is just another step in the step-mash regimen, but using only a cup or so (237 ml) of warm water in a 5-gallon (19 l) grist shouldn’t require any reworking of your math.

Also keep in mind that the overall perception of dryness is influenced by many factors in the beer beyond simply residual sugar content. Carbonation levels, water profile, grist composition, hops profile, and finished pH will all have a synergistic effect that leads to that epic finish we’re chasing.

Without getting deep into water chemistry, if you find your favorite recipe isn’t delivering the finish you’re looking for, it could be as simple as bumping up sulfate levels 30–50 more ppm. Maybe your late hops are bringing a fruit sweetness and fullness that muddies the low terminal gravity. Remember that in all things related to making an excellent beer, “everything is everything.” Using a step-mash profile, you can bring that finishing gravity down and bring yourself closer to that mythic perfect pint.

Want to get the most from your grain? Sign up for CB&B’s Advanced All-Grain Method online class and take your all-grain brew day to the next level.