Adding grain at different points during step mash

[horsepowerwhisperer]

Here's something I've never quite understood about mashing. Going in lower activates beta amylase and gives you more fermentable sugars. Going in higher activates more alpha amylase and gives you more dextrins and unfermentables. So, if you do a step mash with a rest at, say, 145, then ramp it up to maybe 156, is it possible to "use up" most of the starches during the beta phase before the second rest? Or are the starches they work on completely independent? If the former, does it make sense to mash in with base malts at a lower temp, then add specialty grains at the higher rest to effectively save the starches for the alpha stage?

 

[bracconiere]

what i understand of the amylases, alpha is kind of a random chopper, beta chops it's left overs...and beta actually starts work at 130f or so, 145f is just when their both working....alpha works best at 162f.....


that's an interesting brewing idea though....but most specialty malts have already been converted in the kernel before roasting.....

 

[day_trippr]

Check out the three graphs on this page. I think they're fairly illustrative of mash temperature profiles vs wort fermentability..
http://www.woodlandbrew.com/2013/01/mash-temperature-theory.html
Cheers!

 

[horsepowerwhisperer]

Great information, guys, thanks!

The graphs are particularly interesting. So, my main take aways are:
- The grain has a finite amount of starch that can be broken down by either alpha or beta amylase. I originally wasn't sure whether there may be different types of starch molecules that each enzyme broke down. So, for an extreme example, if you mashed in with a single malt at a very low temperature for a long time and let beta tap out its starches, you could still ramp up the mash and let alpha break down different remaining starches into unfermentables. But instead, you basically have one type of starch that can be broken down by alpha, beta or both at the same time. So balancing the time at each rest can make a big difference in final gravity. For single infusion, it's basically just coming up with a compromise number.
- For a really dry beer, you need a very long mash time at lower temperatures, because beta works more slowly than alpha. For a more malty, full bodied beer, you can have a shorter mash time at the higher temps.
-Specialty malts probably don't have the diastatic power to be affected by beta amylase much, so it doesn't really matter if they are added at an early or late rest.

Does that all sound right?

 

[day_trippr]

I think you summarized that pretty well
I had not found those three graphs 'til yesterday. I should save that link...

Cheers!