A Beer Geek guide to Step mashing... Understanding the Science Behind the process

Adding boiling water to raise temperatues.
Infusion step mashing.

So coming up we will be doing an infusion mash on our "Desir et la Nuit" (Belgian tripel with honey). What is an infusion mash?   Well, an infusion mash is a technique for raising temperatures in the mash with boiling water.  It is a step mash.  A step mash is a mashing technique where your mash rests at progressively higher temperatures during the mash.  You don't need a pump, you don't need a direct heat source for your mash tun.  All you really need is your mash tun and a way to boil water.  For those of you who have only brewed single infusion style.  This technique can open your brewing up to all kinds of new possibilities.  And, if you want to make truly world class Belgian style beers,  you will have to step mash.   There are mash elements that can not be created effectively with out step mashing.

Now, it is time to handle the argument against step mashing.  Many of you will say there is just no reason to step mash.  You will claim that modern malted grains are highly modified already and that they do not need to undergo the transformations that occur in a step mash.   To you I say... yeah, you're mostly correct.  Mostly, but not entirely correct.  What?  What the heck...just tell us what you mean.   Relax round eye, I will.   But first you have to take a moment and understand why step mashing is viable and important.

There are more enzymes at work in your mash than beta and alpha amylase.  There is more going on in your mash than the simple conversion of starch into sugar by these enzymes.  Want to make super clear beer?  Even more difficult want to make super clear beer with wheat or rye?  Learn to step mash.  Want to make an authentic Belgian style beer with lots of phenolic punch?   Learn to step mash.   Want to have more fun brewing, and be more active during the mashing process?  Learn to step mash. Want to control your water pH with minimal acid additions?  Learn to step mash (although acid rest for pH adjustment is tough to justify even for me)  Want to reduce chill haze in your beer?  Learn to step mash... I can keep going but I think the point is established.  LEARN TO STEP MASH.

great local home brew store in KC.

Recently I attended a meet and greet at a local home brew shop.   Some very competitive and experienced home brewers were present.   We each brought several bombers to share and try.   When we got to my Belgians, specifically The BSDA, the Tripel, and Alegement (raspberry blonde) the tone of our conversation changed.  They were clearly impressed by what we had made.  Comments abounded about the quality, aroma, and the taste.  One brewer said, and I quote "I'm so f*&kin glad you aren't competing right now".  While that was certainly an ego boost, what was more shocking was their reaction to my process.  Questions broke out about how we did it.  When I answered that each of these beers underwent a step mashing process the responses were all over the board.

There's just no reason to step mash, you're wasting time.  Give me the recipe and I'll prove it to you, a few additional grains can produce the same thing. 
Please be more specific on your process, exact temperatures of rests please...where was your pH, what were your water additions.. what phase was the moon in?
Wait, wait, wait... you actually did a betaglucan rest?

click on this and save it.  trust me you need it.

I know our beer was enjoyed that day.  I know our beer left a big impression.  I know, they know, that we are coming for their medals next year.   And I know I changed at least one of their minds on step mashing.   And 3 of the 4 have qualified for the NHC final rounds at some point in their brewing career/hobby. These are serious brewers.  They had great advice to share with me as well, on reducing oxygen exposure, and maximizing IPA flavors.  It was a great exchange of ideas.

So what are the steps of a step mash?  and more importantly what do they do?  And what are the enzymes you are dealing with at each step?

The ACID rest;  Temperature Range 95 F to 113 F,  Active Enzyme Phytase, Glucanase

Why perform an acid rest?  Well in truth, you don't really need to do an acid rest for the production of pH lowering acid,  unless you are using under modified grains, or unless you want to lower mash pH with minimal chemicals.   Phytase works actively on a molecule found in grains called phytin.  It creates phytic acid which can and will lower your mash pH.   But it takes along time (60 minutes) and really only does well in soft water.  If you ever want to do a true, rustic brew with minimal additions, this is the way to lower pH without chemicals.  It is also a pain in the ass and takes forever.  It is much easier to add some Acidulated Malt to the grist.

Step mashing improves clarity!

The real reason to do a rest at this temperature is to break down beta glucans (gum). Beta Glucan is a gumy carbohydrate that surrounds the starch molecule of a grain.   They get in the way of the amylase and glucans are the chief contributor to chill haze in your beer.   A brief rest at these temperature ranges will allow
glucanase to break down the Beta Glucans.  End result, clearer beer, and slightly better conversion.  Especially important for wheat, and rye.   Ever wonder why Berliner weiss is clear, and American Wheat beer is cloudy?  Glucanase is why.

The PROTEIN rest;  Temperature Range 113 -138 F,  Active Enzymes Proteinase, Peptidase

Why perform an protein rest?  Well actually you should view the two protein related enzymes differently.  They work at different temperatures.

Proteinase works at 131 F to 138 F and is thought to reduce haze with out reducing body.  It breaks long chain amino acids into medium chain amino acids.  You want medium chain amino acids in your beer.

Peptidase works at 113 F to 128 F.  Peptidase breaks medium chains into their components.   So if you want to express maximum esters or phenols in a Heffeweis or in a BSDA, you really should consider a protein rest around 115 F.  The key acid you are trying to maximize is called Ferulic acid.  A Peptidase rest will help you maximize it's availability.  Then all you have to do is use a yeast that is POF+, or phenolic off flavor positive.   If on the other hand you are looking for clarity, without a loss in mouth feel,  you should consider a mash rest that maximizes Proteinase action (136 F).

The SACHARIFICATION rest;   Temperature range 140 F to 162 F, Active Enzymes Alpha and Beta Amylase.

If you are reading this blog,  you probably already know a bit about beta and alpha amylase enzymes.  You have been told that alpha works at higher temperatures and breaks long chain starches into medium chain starches.  You have been told that beta amylase breaks off the branches of longer chain starches into highly fermentable sugars.   Everything you have been told is true.   But let's get more specific.   Beta amylase is active from about 132 F to about 151 F.   A long rest at optimum beta amylase temperatures can produce a highly fermentable wort that will finish dry.   Alpha amylase is active from about 150 F to about 163F.   The optimum temperature is around 156 F.  A rest at alpha amylase will improve the mouth feel of a beer.   Remember beta amylase can not break up the longer chains of starch.   Only alpha amylase can do this.  

A step mash allow you to produce a highly ferment able (Belgian concept of digest able) wort that still has mouth feel.  Our tripel is almost 9% alcohol.   We got over 80 % efficiency and 81% attenuation of the wort.   But the mouth feel is luxurious and rich.   The beer is clear, the color is burnished gold.  You can not do that with out a step mash.  Don't argue this point it is a simple fact of biological chemistry.   You can come close with grain additions, and fining.   But you can not get it exact.

An optimum temperature for an easy mash is 150 F to 152 F.  You kinda get the best of both worlds at that temperature.  Kinda, but not really.   We see high efficiency from step mashing, always in the high 70 s.  And remember we are generally no sparge / partigyle brewers.  So efficiencies approaching 80% from a no sparge are pretty fantastic.

The MASH OUT rest;   Temperature range 168 F +, Active Enzymes - none.  

The point of the mash out is to turn off the enzymes.  The brewing enzymes are, in fact, proteins. Like all proteins they are trying to bind to something.  Trying to work on something, trying to interact.   By raising the temperature above 168 F, you are damaging the working parts of the enzymes and basically turing them off.  They can no longer act on the starches and proteins.   By doing this you create a less viscous wort and a wort that will flow more completely and with more of its desired sugars and flavors into your boil kettle.   Again this is a fact, there is no reason to argue it.  You can argue whether or not it is worth it, but you can't argue the science behind the reasoning.

Conclusion and call to Arms;

Listen, brew how you want.  Brew in the way that is the most fun for you.  But please, don't refuse to understand a technique that can improve your beer just for the sake of narcissism.  Don't stick to one style of brewing because you once shot your mouth off on a brewing forum about it's benefits or lack there of.   Remember, I was once the anti BIAB, anti no sparge, traditional brewing Nazi.  I was the jerk saying they just didn't work.  I was the idiot arguing on forums about the absolute necessity of fly sparging.  I changed by trying new and different approaches.  Not only did it improve my beer, it made brewing loads more fun.   So give this technique a try.  It works.  It will open up subtle flavors to your brewing that you can not develop with out it.  The best brewers in the world use step mashes. It will improve your beer.  And more importantly it is so much fun.

Here are some time tested proven step mash programs.   I have used them all.   They all work.  And yes they take longer.  If you have an automated system, then these are a walk in the park for you.  If not, you'll have to do some math.  We'll cover that math in our next installment.  Planning your Step Mash.

A Step Mash for clarity and body.
100 F for 20 minutes
134 F for 20 minutes
145 F for 30 minutes
155 F for 20 minutes
168 F for 10 minutes

A Step Mash for maximum phenolic expression.
100 F for 20 minutes
113 F for 35 minutes
134 F for 10 minutes
150 F for 30 minutes
168 F for 10 minutes

A simple step mash for maximum extraction of sugar
100 F for 20 minutes
150 F for 45 minutes
168 F for 10 minutes

Step mash for dry beer - dry stout & dry lager like ales
145 F for 30 minutes
152 F for 50 minutes
158 F for 30 minutes
168 F for 10 minutes