goatherder
Fancyman of Cornwood
- Joined
- 23/1/06
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A few posts in this pilsner thread and a recent post in AHA techtalk got me thinking.
I'm looking for some discussion around the step-mash technique of separating out the beta-amylase and alpha-amylase rest. In a nutshell, some mashers do a beta rest at 60-63C and follow this with an alpha rest at 68-72C. The beta rest causes starches to break down into fermentable mono and di-saccharides. The alpha rest breaks these same starches down into longer chain sugars. Noonan presents this method as part of the mash schedule in his book.
There seems to be some support for the theory that well-modified malts finish conversion after 15-20 minutes. Following this logic, a beta rest at 60-63C for 20 minutes or more should give complete conversion of the starches into short chain sugars. If this is correct, what function would an alpha rest serve if there are minimal starches left to break down? Or are the enzymatic reactions more complex than this - do the alpha and the beta amylase act on different sets of source starches for example?
It seems to me, based on this thinking, that a dextrin rest following a sac rest isn't going to achieve anything because there is nothing left for the alpha enzymes to break down. If you wanted to do separate dex/sac rests, then the proper order would be do the high temp first then cool down to the low temp - limiting your time at this temp of course to avoid complete degredation of the dextrins. Or is the answer simply spending a short time in the beta range before stepping up?
I'm not keen on getting into a debate on step mash vs single infusion, I'm just after some comments on this theory. Any thoughts?
I'm looking for some discussion around the step-mash technique of separating out the beta-amylase and alpha-amylase rest. In a nutshell, some mashers do a beta rest at 60-63C and follow this with an alpha rest at 68-72C. The beta rest causes starches to break down into fermentable mono and di-saccharides. The alpha rest breaks these same starches down into longer chain sugars. Noonan presents this method as part of the mash schedule in his book.
There seems to be some support for the theory that well-modified malts finish conversion after 15-20 minutes. Following this logic, a beta rest at 60-63C for 20 minutes or more should give complete conversion of the starches into short chain sugars. If this is correct, what function would an alpha rest serve if there are minimal starches left to break down? Or are the enzymatic reactions more complex than this - do the alpha and the beta amylase act on different sets of source starches for example?
It seems to me, based on this thinking, that a dextrin rest following a sac rest isn't going to achieve anything because there is nothing left for the alpha enzymes to break down. If you wanted to do separate dex/sac rests, then the proper order would be do the high temp first then cool down to the low temp - limiting your time at this temp of course to avoid complete degredation of the dextrins. Or is the answer simply spending a short time in the beta range before stepping up?
I'm not keen on getting into a debate on step mash vs single infusion, I'm just after some comments on this theory. Any thoughts?