…. and the German brewing authors I read so far: http://www.byo.com/mrwizard/1391.html (2nd topic) 

Most likely it was me who was spreading the word on the forums that a mash-out at 76 – 78 C (169 – 171 F) doesn’t kill all enzymes and is also not supposed to. I find this in all the German brewing texts that I read so far and even the ones I didn’t read say the same, according to the German homebrew forum.

 The interesting thing is, that it doesn’t really matter why you believe the mash-out limit is 170F. The American literature (I have only read homebrewing stuff) seems to suggest that this limit is due to excessive tannin extraction at higher temperatures while the German authors emphasize that enzymatic activity needs to be preserved in order to convert additional starches that are released by the lauter process. At the end, both views will have you mash-out below 170 and you will be doing the right thing.  

This subject is not so much a matter of one way will give you a beer and the other won’t. It’s more about brewing geekery and understanding how things are done the way they are done.I was just surprised to see that even some professionals disagree with what I have been saying in the recent past. So I’ll have to make an experiment. Mash-out at 170F, hold for 15 min, take a sample of wort and add a little amount of gelatinized starch to it. Just enough to give me an iodine reaction. Keep it at the 170F temp and wait to see if any conversion is happening. This should be fairly easy to do.