Step VS Single Infusion Mash

[FiddleBrew]

What is the essential difference between doing a single infusion in the upper 140s as opposed to a two-step beginning in upper 140s and finishing in upper 150s? Are you ensured a more complete conversion with the latter?

 

[McKnuckle]

The second, higher temp step is an alpha amylase rest. It will cleave off some longer chain sugars (dextrin) that are unfermentable, giving the beer a bit more body.

Beta amylase, which operates at lower temps, clips off simple maltose molecules which are easily fermentable. But it can’t chop off the bigger chains.

Doing both is similar to what’s called a Hochkurz mash. Usually it’s at the extremes - 145°F and 160°F for example.

Alpha works quickly but beta is slow. So you balance the rest durations according to your desired balance.

 

[FiddleBrew]

I’m confused about your term “cleaving off”.

 

[kevin58]

Cleave means to cut off or break apart.

 

[Gnomebrewer]

The biggest difference I notice is getting complete conversion. I'm sure that a lot of brewers with poor efficiency (and a medium to coarse crush) would improve efficiency by having a rest around 160F. I'm not sure if it's necessarily conversion that's so much faster at this temp, or extraction of starch from the grain, but things move MUCH faster towards completion than they do at lower mash temperatures.

 

[McKnuckle]

Right. It refers to how the starch is converted to different types of sugar. A simple way to understand it is that alpha chops off big pieces, beta snips little ones.

A cleaver is a big a$$ knife.

 

[doug293cz]

Right. It refers to how the starch is converted to different types of sugar. A simple way to understand it is that alpha chops off big pieces, beta snips little ones.

A cleaver is a big a$$ knife.

It's actually much more complex than that. Alpha and beta amylase are both active at room temps, just very slow. Remember the reason the enzymes exist is to convert starch to sugar at close to room temp in order to feed a sprouting seed. So, alpha works at "beta" temps. Alpha also cuts starch chains at random points. So, it creates both long and short chains, as opposed to beta which only creates maltose (length 2 chains). If alpha acts long enough, it will reduce starch to limit dextrins (branched chain polysaccharides that cannot be acted on by alpha or beta), and fermentable sugars. Before all of the beta is denatured (which happens at much lower temps than for alpha) alpha assists beta by creating more chains. Since beta can only act on one end of a given chain, the more chains there are, the more work beta can do.

The primary benefit of higher rest temps is to gelatinize starch granules that are more resistant to gelatinization. Since neither alpha, nor beta, can act on a starch chain until (at least part of) the chain is gelatinized, higher temp rests can make more starch available to be acted on by the enzymes. This can increase conversion efficiency, and therefore mash efficiency.

Brew on

 

[McKnuckle]

I was trying to keep it simple. But that’s great detail, Doug, thank you!