Mashing for All Grain Beer Brewing

by Brad Smith on July 16, 2009 · 14 comments

mash-door-web

Mashing can be a mystical process for first time all-grain or partial mash beer brewers. At its heart, the mashing process uses hot water and natural enzymes to convert complex sugars from malt into simpler sugars that can be readily fermented. We covered the basics of infusion mashing in an earlier article.

At its essence, mashing converts long chains of starches into much shorter sugar chains. Several enzymes that naturally occur in barley malt play key roles in breaking down these sugars. The process starts during malting when the barley grains are germinated and dried. Beta-glucanese and proteolytic enzymes divide branches of complex sugars into shorter chains.

During the mash, the heavy lifting is done by diastatic enzymes that break down the protein and carbohydrate chains that lock up fermentable sugars. Further, as these starches are heated they become more soluble in water, making it possible to extract the sugars and create the sweet wort extracted during lautering. Crushing the grain before mashing increases solubility making it possible to extract a larger percentage of the sugars and starch.

Here’s a summary of the major enzyme groups found naturally in malted barley and their active range:

  • Phytase (86-126 F) – Lowers the pH of the mash. Lowering the mash pH has a number of benefits, though a Phytase rest is rarely used by modern brewers.
  • Debranching (95-112 F) – Helps to increase the solubility of starches resulting in increased extraction for certain malts.
  • Beta Glucanese (95-113F) – Breaks down the gummy heavy starches, which can help improve stability and extraction, particularly for mashes high in proteins and adjuncts such as wheat.
  • Pepidase (113-131F) – Produces free amino nitrogen, which can aid in fermentation.
  • Beta Amylase (131-150F) – Produces maltose, the main sugar fermented in beer.
  • Alpha Amylase (154-162F) – Produces a variety of sugars, including maltose and also some unfermentable sugars. Mashing at the higher end of this range produces more unfermentables and therefore more body in the finished beer.

For single or multi-step mashes, the main step is called the conversion or saccrification step. The bulk work of mashing is done by the alpha and beta amalyse enzymes, both of which are active to some degree in the normal 148-158F conversion step range.

Mashing at a lower temperature of 148-152F activated more beta amalyse, resulting in more maltose conversion. Maltose is the primary sugar preferred by yeast, so a lower mash temperature results in a larger percentage of sugars being fermented resulting in a clean beer finish with higher attenuation, slightly higher alcohol content and less body overall. It does generally take a bit longer for beta amalyse to do its work, so a longer conversion step at low temperature is needed.

Mashing at the high end of the range (154-158F) activates alpha amalyse, resulting in not only maltose but other unfermentable sugars. Less of the sugars will ferment, leaving lower yeast attenuation and additional body in the finished beer. Alpha amalyse completes its work more quickly than beta, so a slightly shorter step time can be used.

The other popular step used by modern brewers is the dough-in rest (protein rest). Usually done at a temperature between 100-120 F, the dough in allows the grains to soak and saturate as well as allowing the key various lower temperature enzymes to begin chopping up longer chains of molecules. This will generally lower your pH slightly, and improve your mash efficiency by a few percent. I personally recommend a 20 minute dough in at a temperature between 100-112F for maximum impact.

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{ 12 comments… read them below or add one }

Brewologist July 29, 2009 at 8:27 am

Great article, thanks! This just opened a whole new world of understanding for with regard to mash temps and the breaking down of complex carbs in the grain. Very informative.

First Stater August 2, 2009 at 12:54 pm

If you mash at a high temperature and add Amylase Enzyme to you get the same end result of a beta amylase mash?

Brew Dude John August 11, 2009 at 12:40 pm

I am going to try a “dough in” next time I brew.

Rep December 25, 2009 at 5:36 am

When using the dough in procedure, will Beersmith assist us in calculating how much water is needed for the particular grist schedule. Then, will it adjust the next infusion volumes and heat to get to the main step?

Brad Smith December 25, 2009 at 7:43 pm

Yes, BeerSmith will do both of those automatically for you if you choose any of the infusion mash profiles.

Bart van Herk April 14, 2010 at 10:51 pm

“Beta-glucanese and proteolytic enzymes divide branches of complex sugars into shorter chains.”

it’s beta- glucanase, not glucanese, and proteolytic enzymes have nothing to do with it: they split proteins, not sugars.

Waldner June 2, 2010 at 6:55 pm

Brad,

I’m also interested in doughing in but can’t find this process in the single infusion mash profiles. Some of the other mash profiles use the term “protein rest” and some use “Dough In” which I assume are the same. Do we have to modify these profiles to include this step?

Brad Smith June 2, 2010 at 6:58 pm

Hi – I believe doughing in is simply the initial infusion. If you use a protein rest, that is actually a separate step which would make it a two step infusion and not a single step mash.

Pete Chrzaszcz May 14, 2011 at 5:27 pm

So if the Alpha and Beta do most of the “lifting” and the respective “Sweet Spots” are 154-158 and 148-152… has anyone started the mash at 148F for 60% of the mash time and reheat the mash tun to 155F for the remaining 40% of the mash time? How to reheat without over heating the bottom?
What are the effects of extracting most if not all of the fermentable sugars?
Will this yield a higher Mash Efficiency? (or is Mash Efficiency purely a function of the sparge?)
Will the end result yield a higher alcohol content?

Thanks, Cheers! Pete

Brad Smith May 15, 2011 at 11:53 am

Pete,
I’ve heard of some people doing this – I believe having a long mash at lower temperatures first is doing to create a lower body beer. Raising the temperature after that would not help much since you would have already broken most of the sugars down at the lower temperature.

Very high extraction (high mash efficiency) is really important for large commercial brewers (its dollars for them) but less so for a home brewer. Attempting to go too far in maximizing your mash efficiency usually results in a stuck sparge (too fine a grain crush) or excessive tannins (from oversparging). Yes – you might get a bit more alcohol in the beer, but again the pennies saved may not be worth it for the homebrewer. Better to through an extra 1/4 pound of malt in and lose the 2% efficiency gain.

Brad

Robert Deal December 17, 2012 at 5:26 pm

Brad,

Another great article. However, I wanted to comment on the terms “dough-in rest (protein rest)” at the end of the article. I believe this is more appropriately divided into a couple of steps.

From John Palmer’s discussion on How the Mash Works (starting at http://howtobrew.com/section3/chapter14-1.html), the pH reduction you refer to is due to phytase degradation of malt phytin that releases phytic acid. The first low-temperature step is the ‘acid rest.’ Palmer also notes that this step is no longer used.

Re “dough-in rest,” Palmer offers that this provides an opportunity for debraching enzymes (limit dextrinase) that survived kilning at the maltings to degrade alpha(1-6) linkages in amylopectin and produce linear starch molecules accessible to amylase degradation. The improvement in extract is likely due to this degradation of limit dextrins, removing obstacles to amylase activity, which decreases (when approaching) and stops (when reaching) hydrolyzing alpha(1-4) linkages when reaching alpha (1-6) linkages.

Finally, Palmer offers the “protein rest” as an opportunity for protease enzymes to degrade larger protein molecules remaining in the endosperm of under-modified malt. Large protein molecules contribute to protein haze and lessen foam stability. As you noted, peptidase is also active at this temperature range, releasing amino acids from peptides produced by protease activity.

Keep up the good work,

Robert

Mark October 21, 2014 at 10:29 pm

Hi Brad,

I’m interested in more detail on the dough in process…

1) How much water is needed per lb of grain?
2) To what temperature should the water be heated prior to adding to the grain in order to hit 100-112F? If BeerSmith can be used to calculate this, can you detail how? I tried messing around with the Mash Adjust tool but it wasn’t making sense to me for use in calculating the dough in specs. Would I use the Infusion Tool? This seems to make more sense but again, I’m not sure. Also, I still need the answer to #1. :-)
3) After the dough in, would I use the temperature of the dough for the calculation of the water temp for the mash in or is there some other means?
4) Am I missing anything? :-)

Thanks!

Mark

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