In that he disusses alpha amylase activity leading to maltose production and operating between 60 and 65 deg C.
Beta amylase activity leads to breakdown of starch to dextrins and occurs between 65 and 70.
I've seen posts around where people refer to beta amylase operating at the lower temp and alpha at the higher and found this home brew wiki which suggests the exact opposite to Fix and with a wider temp range
Beta amylase produces Maltose, the main wort sugar, by splitting 2 glucose molecules from the non-reducing end of a glucose chain. It is therefore able to completely convert Amylose. But since it cannot get past the branch joins, Amylopectin cannot completely be converted by beta amylase. The optimal pH range for beta amylase between 5.4 and 5.6 and the optimal temperature range is between 140ºF (60ºC) and 150ºF (65ºC). Above 160ºF (70ºC) beta amylase is quickly deactivated [Narziss, 2005].
Alpha Amylase is able to split 1-4 links within glucose chains. By doing so, it exposes additional non-reducing ends for the beta amylase. This allows for the further conversion of Amylopectin. The optimal pH range is between 5.6 and 5.8 and the optimal temperature range is between 162ºF (72ºC) and 167ºF (75ºC). Above 176ºF (80ºC) alpha amylase is quickly deactivated [Narziss, 2005]
Now I don't have access to Narziss to see if they have misquoted him and my inclination would be to trust Fix. I have other books and documents about I can check but can those with an inkling of understanding of the brewing scientific principles make it clear who is correct and who is incorrect.? I've re-read both a couple of times to make sure it's not me misinterpreting as someone, somewhere has made a serious error.
Edited by manticle, 24 February 2012 - 04:51 PM.