Originally Posted by Hammy71
Yes, Mashing in low 150s or even the high 190s will dry your beer out.
Uhh, I think you meant high 140's
As others have said, there are different enzymes that activate at different temperatures during the mash and they affect the body and fermentability of the beer.
Your 3 basic enzymes are
- alpha-amylase: does most of the heavy lifting, turning large starch chains and long chain sugars into simple sugars for the yeast. Can only work from one end of the chain (known as the reducing end), and thus cant break down some more complex sugars, espcially ones that have branch points in them.
- beta-amylase: breaks up really long chains into smaller chains for the alpha-amylase. Works from the other end of the chain (the non-reducing end), thus making more available to the alpha-amylase
- limit-dextrinase: breaks down the branch points in the starch chain, making even MORE sugars available to the yeast.
Each enzyme works in a different temp range
- alpha: 155-160
- beta: 140-150
- limit-dextrinase: 140-145
The enzymes are active below those temp ranges, but are much less active. Going much above those ranges will denature (i.e. destroy) those enzymes.
So what to do? Well, for maximum fermentability, you would want to mash around 145, where both limit-dextrinase and beta-amylase are both active, and then ramp up to the 150s to let the alpha-amylase finish off.
This is the basic reason for using a multi-step mash.
If your the nerdy type, brewkaiser.com has a great article explaining all the specifics with lots of pics and graphs. http://braukaiser.com/wiki/index.php?title=Starch_Conversion