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Old 10-09-2012, 11:31 PM   #1
HIlife
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Default Wheat Beer Protein Rest

I'm a molecular biologist who recently got into brewing because it's a lot of what I like about science - pressure + beer. Anyhow, I've been really interested in grain enzymatic activity at mash temps (in that they're nowhere near germination temps) and came up with a practical hypothetical question.

From what I've read, barley beta-amylase is optimally active around 130F(ref), which is in range of a normal protein rest. That's not an issue when mashing barley because its starch gelatinization temperature is above 140F. However, the gelatinization temperature of wheat starch is around 125F(ref), meaning that at protein rest temps the wheat starch is actually available for conversion to the optimally active beta-amylase.

From a practical standpoint, if you are doing a 15-20 minute protein rest on a beer that is 60-70% wheat, should you mash shorter/hotter for the sac rest in order to maintain body and not dry it out like crazy? Or did I just come up with a problem that doesn't really exist?

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Old 10-10-2012, 02:59 AM   #2
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For my hefeweizens I do a 15 minute "protein rest" at 122F, and then raise the temp to 150F for saccarification, and hold there for 60 minutes. My recipe is 50% wheat malt, 50% barley malt. I usually mash other (all-barley) ales at 152F for 60 minutes. I have not tested for starch conversion to see if I could cut down those times. However, I have not had a problem with overly dry wheats. My hefeweizens seem to have plenty of body for style. With the rest I get great "rocky" foam, absent with the all-barley beers. Hope this helps.

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Old 10-16-2012, 10:57 PM   #3
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I guess I'm wondering if it's something that has been investigated before. It makes sense that you would get conversion of the wheat starches at protein rest temperatures, and probably at a higher rate than the typical infusion mash temps. Depending on the conversion potential during the protein rest and the proportion of wheat in your grain bill you could do some interesting things with the saccarification rest that you wouldn't be able to do with an all barley beer.

Then again, I'm too new at this to know what I'm talking about, so I could be totally wrong.

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Old 10-17-2012, 12:45 AM   #4
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Well, beta-amylase can only cleave maltose off the ends of the larger molecules. Perhaps, especially at 130, alpha amylase is slow enough that there's not an appreciable increase in dryness in the finished product.

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Old 10-17-2012, 02:57 AM   #5
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Beta-amylase can completely convert linear amylose, but it can't chew past the 1-6 linkages in amylopectin (the branch-points in the branchy starch molecule). From the sources I found, wheat starch is somewhere around 15% amylose with the rest being amylopectin. If you can imagine starting the sacc rest with >10% of your total conversion (.15 * 70% wheat grain bill) complete, you can see that there is potential for different mash techniques when using a high wheat grain bill and a protein rest that is not possible with a barley only beer.

Basically, the kinetics of the mash *have* to be different between the two scenarios but it's a question of whether it's different enough to allow for variations in technique. Maybe you can do something a little fancy with a high wheat mash, maybe you can't. I'm sure someone who is way more knowledgable has thought of it before and either they figured out that it doesn't matter, or there's an under-utilized wheat beer mashing technique floating around somewhere.

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Old 10-17-2012, 05:23 AM   #6
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The attached is the profile that I have used for wheat beers for years. It is from Eric Warner's monograph in the AHA series. It makes a really nice beer and I adopted it so long ago that if I ever did try to figure out how it works I've long forgotten my conclusions. Note that there is a protein rest but the most interesting thing is that the decoctions are held at 160 °F. I guess this gives alpha amylase a chance to do its thing such that when returned to the main mash there are lots of reducing ends available to beta amylase.

wheatdecoc.jpg  
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Old 10-18-2012, 04:03 AM   #7
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Wow, ajdelange, you are a patient soul! Three and one half hours of mash time for a wheat beer is past the limits of my patience.

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Old 10-18-2012, 04:36 AM   #8
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Lagers require triple decoctions so wheat is a short brew day.

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Old 10-19-2012, 02:50 AM   #9
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So AJ, what kind of attenuation do you normally see with that mash schedule? It seems like you would get as close to 100% conversion as is possible. Also, does boiling for 20 minutes completely denature grain enzymes or can they refold after being brought back into the main mash (or are they just insanely stable)?

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Old 10-19-2012, 02:52 AM   #10
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Quote:
Originally Posted by HIlife View Post
Also, does boiling for 20 minutes completely denature grain enzymes or can they refold after being brought back into the main mash (or are they just insanely stable)?
They denature...that's why he does the rest at 160--to convert before he denatures
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