Learning Lab: Sweet Mash Choices

Get back to basics and focus on the starch-conversion mash step, to better understand which mashing regime best fits the beer you want to brew.

Jester Goldman Mar 18, 2020 - 11 min read

Learning Lab: Sweet Mash Choices Primary Image

Beer almost seems preordained.
The grain comes packed with all it needs to convert starches into sweet wort. It’s magical: All you need to do is add water, hold the whole thing in the right temperature range, and let the amylase enzymes do all the work. This should make it all so simple, but you could easily be overwhelmed by all of the different mashing schedules that various brewers tout. These can largely be distinguished by the recommended number of steps or temperatures at which you let the mash rest. Each step offers some particular effect on the process or the final beer.

We can learn about all of those choices some other time. For now, let’s get back to basics and focus on the single most important one: saccharification, where starches are converted into sugar.

Malt Conversion and Temperature

Malt conversion depends on two different enzymes, alpha and beta amylase. Both break down long starch molecules, but they work in different ways. Alpha amylase can step in anywhere in the starch chain, creating a mix of longer, unfermentable sugars as well as some smaller ones that the yeast can digest. Beta amylase attacks the starch from the ends, chomping off small fermentable chunks of maltose.

Single-Step Mashing
While both enzymes work within the standard saccharification range of 146–156°F (63–69°C), each one has its favorite zone. Alpha amylase prefers 154–162°F (68–72°C) while beta amylase likes it cooler at 130–150°F (54–66°C). When you choose to do a single-step infusion mash, you’re making a trade-off between the two extremes. Mash at the higher end, and you’ll get more unfermentable dextrins, producing a sweeter, heavier beer. If you stick to the lower end, you’ll get a lighter-bodied, more alcoholic beer, although it will likely take a bit longer for the beta amylase to chomp through the starch. Many brewers split the difference and aim for about 152°F (67°C) to get a medium-bodied beer.

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Dual- Stage Saccharification
A single-step mash is about as easy as all-grain brewing gets, but of course, some clever brewers have made it complicated by following a two-stage saccharification step. Strictly speaking, this isn’t a “single-step” mash because there are two temperature rests that hit the lower end and then the higher end of the saccharification temperature range. You might think that this is functionally equivalent to picking a mash temperature in the middle of the range, but you’d be wrong. Instead, this approach produces the lightest, crispest beer with a dry finish. About half the mash time is spent at the lower temperature, which lets the beta amylase produce plenty of maltose. Then, the mash is heated to the higher range, so the alpha amylase can break down any remaining starch. The result is highly efficient and quite fermentable.

Meanwhile, Back in the Lab

As promised, this lab focuses on the starch-conversion mash step. We’ll brew a set of beers that cover the possibilities outlined above. This includes three single- step brews at different temperatures and one dual-stage saccharification beer. In this lab, I also recommend that you measure the starting and finishing gravities, not to match the recipe’s estimate, but as additional data for the evaluation.

All of these will be based on the same mini-mash brew-in-a-bag (BIAB) recipe.

Volume (after boil): 1 gallon (3.8 liters)
OG: 1.052
FG: ~1.012
Grain: 2 lb (907 g) crushed 2-row malt
Hops: 0.25 oz (7.1 g) Cascade pellet [7.0% AA] at whirlpool
Yeast: ½ packet of Safale US-05

Single -Step Process
Each of the single-step beers will follow the same process, just aiming for a different mash temperature. Some of the steps below list three different temperatures, one for each of the beers, “beta,” “mixed,” and “alpha,” depending on which enzyme is favored. For those steps, select the temperature that matches the sample beer you’re making.
Directions: Place the crushed malt into a nylon grain bag and set aside. Heat 3 quarts (2.8 l) of water to [beta:156°F (69°C), mixed: 161°F (72°C), alpha: 166°F (74°C)]. When the water reaches temperature, move the pot off the burner.

Dip the bag of malt into the pot and swirl it around to make sure that all of the grain is thoroughly wet. Check the temperature of the liquid. We’re aiming for [beta: 146°F (63°C), mixed: 150°F (66°C), alpha: 156°F (69°C)]. You may need to heat the mash a little or add a splash or two of cool water. In either case, stir the bag in the pot to normalize the temperature.

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Once the water is at the target temperature, cover the pot and let the grain bag sit. In winter, you may want to wrap it in a blanket for insulation. Mash for about 60 minutes but check the temperature halfway through. If it has dropped more than a couple of degrees, you should put the pot back on the burner to kick the temperature back up to the appropriate target.

At the end of the hour, heat another 2 quarts (1.9 l) of water to 170°F (77°C). Lift the grain bag out over the pot (if you have a strainer that can sit on the edge of the pot, that would be great). Pour the hot water over the grain and into the pot to rinse a little more of the malt sugars out.

Top up the pot with another quart (946 ml) of water. Boil the wort for one hour, then take the pot off the burner. Stir the hops into the wort for a whirlpool addition. Cover and let sit for 20 minutes. Then chill the wort to 70°F (21°C), transfer into a gallon (3.8 l) jug, topping up with water if necessary. Pitch the yeast and put on the airlock.

Ferment each mini batch at about 70°F (20°C). Once fermentation is complete, bottle the batch with about 0.4 oz (12 g) total dissolved priming sugar.

Dual-Stage Process
This process will be very similar to the one above but will hold the mash first at the lower beta amylase–optimized temperature, then at a higher one for alpha amylase.
Directions: Place the crushed malt into a nylon grain bag and set aside. Heat 3 quarts (2.8 l) of water to 154°F (68°C). When the water reaches temperature, move the pot off the burner.

Dip the bag of malt into the pot and swirl it around to make sure that all of the grain is thoroughly wet. Check the temperature of the liquid. We’re aiming for 144°F (62°C). You may need to heat it a little or add a splash or two of cool water. In either case, stir the bag in the pot to normalize the temperature.

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Once the water is at the target temperature, cover the pot and let the grain bag sit. In winter, you may want to wrap it in a blanket for insulation. Mash for about 30 minutes.

Next, lift the grain bag out of the kettle and put the pot back on a hot burner. Heat the pot up to 156°F (69°C). Once the liquid is at the target temperature or a degree higher, place the grain bag back into the pot and stir around. As before, when the mash has reached the target temperature, take the pot off of the burner and let it sit for another 30 minutes.

At the end of the mash, follow the single- step process steps to rinse the grain, top up for the boil, add the hops, ferment the beer, and then bottle it.

Evaluation

Give the beers 2 or 3 weeks to carbonate and then set up your tasting session.Your evaluation should focus on the malt character, mouthfeel, and overall balance of the beer.

As in our other labs, you should write up your impressions and associations for the aroma and flavor for each beer. Your biggest learning, though, will come as you compare the beers to one another. There are a number of qualities you can assess them against, such as sweetness, malt flavor, and body. In general, you should expect the beers to fall into order as dual-stage, beta, mixed, and alpha, with the dual-stage beer being the lightest, driest of the group.

This order should also be in line for the finishing gravity, which is an indicator of the remaining sweetness and body. The gravity measurements will let you calculate the alcohol level of each beer. It might be a little harder to taste the difference in alcohol level, but see if you can detect the difference among the samples.

After noting the obvious observations, start to look at second-level effects, such as how the perception of hops shifts among the beers or how much you enjoy the finish. You can extrapolate from this experience to understand which mashing approach might fit particular beer styles.

That’s key because there is no “right” temperature for starch conversion. It all depends on the effect you want in a particular beer. Now, you should have a better handle on that.

Photos: Matt Graves/www.mgravesphoto.com

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