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Old 12-29-2012, 03:45 AM   #1
Rev2010
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I was wondering, a lot of pro german recipes, especially wheat beer recipes, call for rests such as 149 for 30 minutes and 158 for 30 minutes. I'm asking because many say full conversion is often done in as little as 15 minutes. Even if conversion takes longer I would think by 30 most mash conversions would be complete no? Of course I still do 60 minutes typically for my main sacch rests for good measure but I got to wondering - if most or all of the conversion is done in the quicker time frame than what does the higher rest do? Does it just convert what remains unconverted into the longer chain sugars or does the higher rest do anything to change what was already converted at the lower 149 temp?

That being said, if the higher rest does nothing to the already converted chains, then why not just rest in the middle... say at 154 for the sacch rest? Any knowledge on this would be greatly appreciated!


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Old 12-29-2012, 03:49 AM   #2
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I've read a few sources say conversion is done in 15-20 minutes. I've read a bunch more say that's false. MOST of the conversion is done quickly, but not all. So I'm guessing you're right, the last one would just take what wasn't converted in the first rest into more dextrinous and unfermentable wort. I'd be inclined to just rest in the middle as well.
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Old 12-29-2012, 04:27 AM   #3
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My last wheat which used raw white wheat took two hours to convert, tested with iodine.

I think it depends on the grain bill to an extent. Highly modified malts will be different than under modified.

Enzyme activity is also highly dependant on temperate, so a low starting temp will not convert as fast, leaving some for the higher temp to complete.

With under modified malts, the acid rest is/may be necessary, but it requires low temps and a lot of time. These enzymes don't convert starch, and are not active at higher temps when starch conversion occurs.

So, depends what you are working with, but with highly modified malts, I believe there is low impact to steps, based on what I have read.

 
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Old 12-29-2012, 04:45 AM   #4
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I was struck in Stone's book about how they called for something in the range of 20 minute mashes in the recipes they provided. Much shorter than typical homebrew mashes.

As for the benefit of multi-step mashes, beta and alpha amylase work best at different temp ranges, so even if the betas are done doing all their work at 149, the alphas may have more to do at a higher temp.
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Old 12-29-2012, 06:05 AM   #5
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Quote:
Originally Posted by BrewKnurd View Post
As for the benefit of multi-step mashes, beta and alpha amylase work best at different temp ranges, so even if the betas are done doing all their work at 149, the alphas may have more to do at a higher temp.
I hadn't really considered that since I know there is an overlap at that temp range (149 or so) between beta and alpha but looking at it again it makes more sense the differences that might be imparted at those ranges. This has given me more faith in the rests I'd been often doing for certain beers. I always did notice a difference, for example, in my single infusion hefe's... they are never anywhere as good as my multi-step ones. Thanks for pointing this out, given me something to think about and maybe experiment a little further with.


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