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Old 03-10-2009, 02:03 PM   #1
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Default Proteins/Aminos, protein rests, and beer body

I have a very basic understanding of this but there are gaping holes so I'll just start at square one on this topic.

What exactly does a protein rest do? And how?

Most say that a protein rest is not necessary with today's malts...why is this so? What's the harm in doing one anyway?

I've read some (Kaiser?) say that they believe the proteins have a greater effect on beer body (and mouthfeel?...and head retention?) than previously thought. Any comments on that? What would be a good experiment to test this?

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Old 03-10-2009, 02:33 PM   #2
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I'll take a stab at it, but this is a rudimentary explanation and I'm not necessarily confident in it... without texts to reference.

Proteins come in all different sizes. The large ones cause haze, the small ones may add some mouthfeel, etc., but without the presence of medium-sized protein molecules, your head retention suffers. The proteins in this size-range are small enough to be carried to the surface by CO2 coming out of solution, but not too big to cause haze.

In a protein rest, enzymes break down proteins to smaller proteins. In well-modified malt with a high SNR, these are already broken down. So, leaving them alone will result in a better head retention. Giving them a protein rest in the temperatures that are ideal for the enzymes that break them down will break them down to be too small to get carried to the surface by CO2.

I humbly submit this explanation knowing that I may be off on some of it. If I am, feel free to tear me a new one.

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Old 03-10-2009, 02:43 PM   #3
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Thanks. But I didn't quite get this:

Quote:
Giving them a protein rest in the temperatures that are ideal for the enzymes that break them down will break them down to be too small to get carried to the surface by CO2.
Seems if small proteins get carried to the surface by CO2 then breaking them down to smaller ones they would still get carried to the surface.

Quote:
In a protein rest, enzymes break down proteins to smaller proteins. In well-modified malt with a high SNR, these are already broken down.
Would it be pertinent to this topic to describe the relationship between SNR (soluble nitrogen ratio) and proteins? I've seen this written before but it's written just like you did...without any real correlation between them.
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Old 03-10-2009, 03:05 PM   #4
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Quote:
Originally Posted by SpanishCastleAle View Post
Thanks. But I didn't quite get this:
Sorry, I just meant that the proteins get broken down to be too small. So in the finished beer, they don't get carried to the surface as easily by CO2 coming out of solution and rising to the top (i.e., they don't create as much of a head).

Quote:
Originally Posted by SpanishCastleAle View Post
Seems if small proteins get carried to the surface by CO2 then breaking them down to smaller ones they would still get carried to the surface..
Well, if if they get broken down so small, they may get carried to the surface, but aren't substantial enough to contribute to the head. That might be one of the parts I'm off about.

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Originally Posted by SpanishCastleAle View Post
Would it be pertinent to this topic to describe the relationship between SNR (soluble nitrogen ratio) and proteins? I've seen this written before but it's written just like you did...without any real correlation between them.
Noonan does a much better job explaining it than I could.
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Old 03-10-2009, 03:48 PM   #5
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I would say that large molecular weight proteins contribute to haze, medium molecular weight proteins are foam positive, low molecular weight proteins (free amino nitrogen) is foam negative but a certain amount is required.

Breaking down high to medium will increase clarity and improve foam.

Breaking down medium to low will harm foam (assuming the FAN level of the wort is otherwise adequate). So protein breakdown is a balancing act. SNR or the Kohlbach index will provide you an indication of how much protein breakdown took place in malting. Conventional wisdom is that for most modern malts (SNR > 40) protein breakdown sufficient for clear beer with good foam has already taken place during malting and that further protein breakdown in mashing will do more harm than good.

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Old 03-10-2009, 04:12 PM   #6
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This is the general concensus on the topic of preteins and it all makes sense until you read the likes of Fix and Horst (??, IIRC) who claim that even with well modified malts a protein rest has the "perceived" contributary effect on head retention and malt character.

I am not yet convinced that the science and perceived effect agree on this topic yet. At the least, I have noticed a considerable increase in clarity in my beers with no "perceived" degredation in heading ability by utilizing a short 10 to 20 minute rest at ~113*F to 120*F.

In this, I have also realized that less fining is needed and that cold conditioning is most effective at obtaining that Kristal quality.

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Old 03-10-2009, 04:18 PM   #7
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Quote:
This is the general concensus on the topic of preteins and it all makes sense until you read the likes of Fix and Horst (??, IIRC) who claim that even with well modified malts a protein rest has the "perceived" contributary effect on head retention and malt character.

I am not yet convinced that the science and perceived effect agree on this topic yet. At the least, I have noticed a considerable increase in clarity in my beers with no "perceived" degredation in heading ability by utilizing a short 10 to 20 minute rest at ~113*F to 120*F.
This is exactly my perception but I haven't really tested it. And at the time I think I was more bummed about poor clarity than I was worried about head retention...so I may have just noticed improved clarity (which may or not be due to the protein rest) and not noticed reduced head retention. Then again...I often do use a little Carapils in many grain bills (maybe this is why).
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Old 03-10-2009, 04:24 PM   #8
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Fix was a big proponent of no protein rest for SNR > 40 in the current editions of his books and in some posts made on HBD.

He did 40-60-70 for SNR > 40 and 50-60-70 otherwise. In the former schedule, he emphasized using boiling water infusion so that no or minimal time was spent around 50.

I recall him saying something like "I now agree with Narziss and others..." in Principles of Brewing Science which indicates that he previously held a different position. I have not read the first edition of that book.

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Old 03-10-2009, 04:26 PM   #9
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remilard, great post. You said it much more eloquently than I.

GilaMinumBeer, interesting. I have brewed a couple batches early on in my brewing career with a protein rest around 120°F and with well-modified continental pilsner malt. The results were low to medium head formation/retention. Since I've switched to higher temp. protein rests, my head formation/retention has improved a lot.

Perhaps the best head formation/retention comes from brewing with under-modified malt and conducting true protein rests. That's what Moortgat does and look at Duvel.

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Old 03-10-2009, 05:02 PM   #10
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I'm testing a protein rest in my current lagers. I can only compare to my memory of last years lagers unfortunately. Last year I did a 5 min rest for all my lagers. This year I'm doing 20 min. (20,20,20 - 122F, 148F, 158F, then 168 mashout, drain immediately) My main goal is to improve body. We'll see what happens to head retention. Just based on foaming at the various steps prior to kegging, the head will be very good on these.

My take on the statement "today's well-modified malts" is that this statement is largely directed at having to worry less about chill haze. I also find that when the statement is made that "a protein rest can actually harm head formation in today's malts", that the time frame is rarely given. I think therefore many people take this to mean ANY protein rest. I did read somehwere recently (Dornbusch Helles book?) that the time was OVER 30 min. for this to happen.

I was planning on a two brew weekend (lagers) sometime soon to compare the same recipe with step mash vs decoction. Maybe I'll switch that to protein rest vs no protein rest. This gets a little tricky as there will be some starch conversion during the protein rest. I'll have to go by conversion rate, not strictly time for the steps to avoid any influence there. I'll check the brix after my 148F rest with the p-rest version and then for the no p-rest version, do the step to 158F when the brix reaches the same level as after the 20 min. at 148F for the p-rest version.

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