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Old 06-24-2011, 04:46 PM   #1
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Default How to know when a protein rest is needed?

I was hoping this question would be answered in reading Designing Great Beers, but it wasn't.

What are the rules for when a protein rest is necessary? What publications cover this topic?

Thanks!

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Old 06-24-2011, 04:56 PM   #2
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Can't quote any specific sources, but I have the notion that a protein rest is best used with mashes that contain wheat, rye, oats or other high protein (beta-glucanese?) ingredient that may cause sparging problems, even with a mash out.

Or at least that's one reason for it...

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Old 06-24-2011, 05:25 PM   #3
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I believe I've read that a protein rest is necessary when not-fully modified malts are used? Is this true? And, what malts are considered "not fully modified"?

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Old 06-24-2011, 06:10 PM   #4
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What I remember from listening to Brewstrong is that a protein rest will help to modify under-modified malts as has been suggested, but also to modify unmalted grain like raw wheat and oats.

The only style I use a protein rest for is witbier which uses over 50% of the grist as wheat and oats. I even used flaked wheat and oats which helps since that provides starch that has been pre-gelatinized.

As far as which grains are undermodified, they will usually tell you. One that I have used recently that I know is undermodified is Continental Pilsner malt. Most US malts are well modified. Remember that "modified" refers the malting process. The better the malting is done, the more well-modified.

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Old 06-24-2011, 06:11 PM   #5
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Malts these days are so well modified, which includes wheat malt, you will really only need a single infusion.

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Old 06-24-2011, 06:16 PM   #6
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There are some brewers who never do a protein rest. I used to be one of them and I got great results, but recent experimentation has made me a convert to the Fix mash schedule. (15 mins @ 40C, x mins @ 60C, y mins @70C where x+y=60) Adding a short protein rest has been shown to improve efficiency in some situations. I batch sparge and my efficiency went up from about 75% to about 82% when I started using the Fix technique.

The general wisdom is that a protein rest is most beneficial when using a high percentage (over 33%) of protein rich adjuncts such as any unmalted grain, or malted oats and rye as mentioned above. This will help improve wort clarity and decrease mash gunkiness for the sparge. It can also be beneficial (from the point of view of efficiency) for undermodified grains as you mention. These days that mostly means authentic Bohemian pilsner malt and 6-row.

So, to sum up, I would say a protein rest is never necessary, a short one will never hurt, and it's mostly beneficial when you are mashing lots of high protein adjunct or if you are trying to improve efficiency, especially when using undermodified malts like Bohemian pils or 6-row.

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Old 06-24-2011, 06:32 PM   #7
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I would add that a short protein rest is key when using well-modified malts and malted wheat, rye, and the like.

I've been doing protein rests for the last several batches and, for one reason or another, they end up taking 20 minutes or so. I believe this has affected head retention for these beers, as in "very little head retention". Of note here is that these are beers that are traditionally known as super head retention samples (e.g., wheat).

I've looked into this and it appears that I should shorten the rest to get both the protein breakdown as well as not too much of it. Now I'm thinking in terms of 5 minutes or so IF I do a protein rest at all.

Your mileage may vary.

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Old 06-24-2011, 06:57 PM   #8
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Yeah, with well modified malts you never want to do more than 15 mins for a protein rest. I try to keep mine in the 10-15 min. range for most of my brews.

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Old 06-24-2011, 09:58 PM   #9
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Disclaimer, I've never bothered with a protein rest, but have thought about including one on some of my wheat-heavy brews, so thought I would throw my theory out and see if it makes sense to anyone else.

Since I can't help but try to figure out the science behind things, I was trying to remember what the actual enzymes were that the protein rest is meant to activate, so I went back to John Palmer to see what he said (apologies if this has been updated in the newer versions, I don't have mine in front of me).

If he's correct, there are actually two groups of enzymes active at typical protein rest temps. The first concern the proteases that will help to break down proteins in under-modified malt. These proteins weren't fully broken down during malting, so cutting them into smaller pieces will facilitate the release of starch from the grain. This will also help to cut down on soluble proteins in the wort, which can help if you get chill haze, but if you go too far you can start to diminish the body of the beer.

The second set of enzymes are the beta-glucanases that ASantiago mentioned that will break up the larger starches present in wheat and oats into smaller pieces so that you can avoid problems like stuck sparges. This would also presumably release easier substrates for the amylase enzymes. He even mentions the possibility of aiming on the lower end of the "protein rest" (~100-110F) if you want to avoid the protease activity.

So here's my thought, check and see if it makes any sense.
1. If I was using flaked/raw/rolled wheat or oats (since not malted, would fall under the under-modified category) a typical protein rest around 120-130 would be a good call, both to break down some of the proteins and to break down some of the gummy starches.
2. If I was using malted wheat or oats (not sure about rye?) I could assume that so long as it wasn't under-modified a protein rest probably isn't necessary. However, a short protein rest, or even a short rest below protein temps (100-110) might help to break down some of the starches, especially if I was having stuck sparge problems.
3. If I wasn't using any or very little wheat or oats, the protein rest might not give any appreciable benefit unless I was also having trouble with another factor, like chill haze.

Sorry for the long post, but does any of that makes sense?

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Old 06-24-2011, 10:10 PM   #10
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That's essentially correct, as far as I know.

With flaked/raw grains the protein rest is most useful when they constitute a large percentage (>33%) of the mash.

When using malted wheat, a protein rest is probably not necessary, but if you use a large amount of oat or rye malt it might be a good idea as these are generally even higher in protein than wheat.

If you are using little or no adjunct, the beta-glucanase activity can sometimes still be beneficial to your efficiency. If I batch sparge without a protein rest I get around 78% efficiency; with it I get about 82% for typical mashes. That is my main reason for doing a protein rest in my low/no adjunct beers.

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