Protein rest PH
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5.4 or thereabouts
biertourist
Well-Known Member
I just finished reading Michael Lewis & Tom Young's text "Brewing Second Edition" on a really long series of flights from Dublin to Seattle yesterday and they were pretty adamant that very little protelytic enzyme survives the malting process in highly modified malts and that the traditional "protein rests" are a huge misnomer.
--I was completely shocked but they mentioned it again and again in multiple chapters... They treated it as if it was a very common myth that was well-known as a myth by modern brewing science...
Now that I saw this and AJ chiming in on the thread I figured this was a good a time as any to bring it up.
I'll go get the exact quote later; they mentioned only one enzyme out of the suite of protelytic enzymes was likely to make it into the mash and that it's contribution would be very much limited.
(Yes, it's a pretty world-rocking assertion; if it wasn't the 2nd edition of an incredibly respected professional brewing text I would have immediately discounted it.)
Adam
--I was completely shocked but they mentioned it again and again in multiple chapters... They treated it as if it was a very common myth that was well-known as a myth by modern brewing science...
Now that I saw this and AJ chiming in on the thread I figured this was a good a time as any to bring it up.
I'll go get the exact quote later; they mentioned only one enzyme out of the suite of protelytic enzymes was likely to make it into the mash and that it's contribution would be very much limited.
(Yes, it's a pretty world-rocking assertion; if it wasn't the 2nd edition of an incredibly respected professional brewing text I would have immediately discounted it.)
Adam
biertourist
Well-Known Member
Here's the direct quote:
"The most obvious time to degrade protein is during malting, when a full complement of proteases and peptidases are present. The vast bulk of amino acids are thus formed in malting, not mashing. In the malting of well-modified malt, more than 40% of the protein is broken down to soluble components. The “protein rest” in mashing is thus probably a misnomer because extensive proteolysis is unlikely in mashing due to the many protease enzymes that are inactivated during the kilning and the short duration of the low temperature stand. Solubility characteristics commonly define barley proteins. The less easily dissolved proteins dominate in high-protein barley. The ratio of the total soluble nitrogen (TSN) to total malt nitrogen (TN) is expressed on malt spec sheets as the Kolbach index. Too high and you’ve got problems associated with too much proteins in the beer like chill haze. Too low and there is no foam on the beer. Two row barley malt has lower nitrogen and protein content and also lower husk content. Six row barley malt has a higher nitrogen and protein content (is less modified) and a higher husk content. It has a higher diastatic power (more enzymes) so it is the malt of choice when large amounts of cereal adjuncts like maize grits are used (in double mashes). The extra husk aids in providing a lautering filterbed."
Adam
"The most obvious time to degrade protein is during malting, when a full complement of proteases and peptidases are present. The vast bulk of amino acids are thus formed in malting, not mashing. In the malting of well-modified malt, more than 40% of the protein is broken down to soluble components. The “protein rest” in mashing is thus probably a misnomer because extensive proteolysis is unlikely in mashing due to the many protease enzymes that are inactivated during the kilning and the short duration of the low temperature stand. Solubility characteristics commonly define barley proteins. The less easily dissolved proteins dominate in high-protein barley. The ratio of the total soluble nitrogen (TSN) to total malt nitrogen (TN) is expressed on malt spec sheets as the Kolbach index. Too high and you’ve got problems associated with too much proteins in the beer like chill haze. Too low and there is no foam on the beer. Two row barley malt has lower nitrogen and protein content and also lower husk content. Six row barley malt has a higher nitrogen and protein content (is less modified) and a higher husk content. It has a higher diastatic power (more enzymes) so it is the malt of choice when large amounts of cereal adjuncts like maize grits are used (in double mashes). The extra husk aids in providing a lautering filterbed."
Adam
Adam, thanks for including the quote. Yes, my take on the gist of the quote is that a protein rest is unnecessary. That has been fairly widely disseminated, but there are still some that insist its needed. I agree that its not needed and is often counterproductive. Only a 'purposely' poorly modified malt should be subjected to a protein rest since most modern malts are very well modified.
When ever this comes up I always tell the story of the fellow from the local regional with a PHD in biochem who gave us a lecture on mashing biochemistry and his slide on the subject of the protein rest. It had three squares. One said "protein rest" in it and the other two had pictures of Santa Claus and the Easter Bunny. And earlier in this thread we have the opinion of 2 respected brewing scientists and that opinion seems unassailable in its logic.
Yet in the two times I have skipped a protein rest (both on the same day) I got beers which had protein based chill hazes that persisted throughout the time I had the beers. A year in cold storage was not sufficient to drop it all.
And of course we've all heard that not only do we not need a protein rest because it doesn't result in proteolysis but that we had best not do one because if it's too long the beer will have no head (the counterproductive aspect that Martin alludes too - at least I think that's what he must have in mind).
In most of my brewing (lagers) I use the traditional Dreimaischverfahren which has a long rest in the mid 120's (F). It's long because the rest mash is held in that range during the entire time of the second decoction. I cannot say that I would have a protein haze if I skipped the protein rest (this is not the same malt that threw one for me with the ales) but I must say the head is fantastic on these beers. I also cannot say that the head would be poorer if I skipped the protein rest and that's because I have never skipped it.
Thus, while I agree in principle with what these guys are saying I have seen that this now widely accepted wisdom does not seem pertain in all cases. It probably has to do with degree of modification, TSN etc. As I have never seen detriment from a protein rest but have seen it when I omit the protein rest I continue to perform them. At worst I am wasting a fair amount of time.
Please don't take this as advice from A.J. that you should do a protein rest. As with everything else I think people need to experiment to determine what works best for them given their materials and methods.
Yet in the two times I have skipped a protein rest (both on the same day) I got beers which had protein based chill hazes that persisted throughout the time I had the beers. A year in cold storage was not sufficient to drop it all.
And of course we've all heard that not only do we not need a protein rest because it doesn't result in proteolysis but that we had best not do one because if it's too long the beer will have no head (the counterproductive aspect that Martin alludes too - at least I think that's what he must have in mind).
In most of my brewing (lagers) I use the traditional Dreimaischverfahren which has a long rest in the mid 120's (F). It's long because the rest mash is held in that range during the entire time of the second decoction. I cannot say that I would have a protein haze if I skipped the protein rest (this is not the same malt that threw one for me with the ales) but I must say the head is fantastic on these beers. I also cannot say that the head would be poorer if I skipped the protein rest and that's because I have never skipped it.
Thus, while I agree in principle with what these guys are saying I have seen that this now widely accepted wisdom does not seem pertain in all cases. It probably has to do with degree of modification, TSN etc. As I have never seen detriment from a protein rest but have seen it when I omit the protein rest I continue to perform them. At worst I am wasting a fair amount of time.
Please don't take this as advice from A.J. that you should do a protein rest. As with everything else I think people need to experiment to determine what works best for them given their materials and methods.
biertourist
Well-Known Member
This whole thread is now like something out of the twilight zone!
Aj telling us to ignore the brewing text / literature and then an appeal to personal experience?? -My world has truly been rocked today! ; -)
What's next? An official endorsement of PH 5.2 salts?? ;-)
Mabrungard, had the quote only said "protein rests are unnecessary" -it wouldn't really have been interesting. What's interesting is that its saying "protein rests don't exist". It's more akin to the "Easter bunny" slide that AJ mentioned.
It's an incredibly interesting subject especially when you start to see the big names stack up on both sides of the issue... Someone needs some funding to do some post doc research to put this one to bed, me thinks. -Don't the big maltsters have money available for this sort of thing?
Adam
Aj telling us to ignore the brewing text / literature and then an appeal to personal experience?? -My world has truly been rocked today! ; -)
What's next? An official endorsement of PH 5.2 salts?? ;-)
Mabrungard, had the quote only said "protein rests are unnecessary" -it wouldn't really have been interesting. What's interesting is that its saying "protein rests don't exist". It's more akin to the "Easter bunny" slide that AJ mentioned.
It's an incredibly interesting subject especially when you start to see the big names stack up on both sides of the issue... Someone needs some funding to do some post doc research to put this one to bed, me thinks. -Don't the big maltsters have money available for this sort of thing?
Adam
Please understand that I am not saying 'ignore the text'. My only basis for saying that would be if I thought the text were wrong and I don't. What I do think is that what it says doesn't cover every situation and that I (and others) have seen protein hazes from Maris Otter (that's the cultivar that always comes up). It's entirely possible that there may be an explanation for this which is consistent with what's in the text.
Now that said there are errors in that book. I don't know what any of them are but I know they are there because there always are some. That's what the little 'errata' slips that come in lots of textbooks are there for. These are the things that keep authors from sleeping at night. Most are small and easy to spot if you are familiar with the material but if you are familiar with the material why are you reading the book?
I don't think this really needs any more research. Some malts will throw a haze and some won't. Further modification should fix the 'problem' otherwise do a protein rest. For most of us that isn't a big deal but remember that a mega wants the beer out the door at minimum cost, labor and capital expense. If they can skip one of the rests they can make more money.
I did also point out that it seems contradictory that a rest that supposedly does nothing to proteins is also thought to destroy the proteins responsible for head formation.
Now that said there are errors in that book. I don't know what any of them are but I know they are there because there always are some. That's what the little 'errata' slips that come in lots of textbooks are there for. These are the things that keep authors from sleeping at night. Most are small and easy to spot if you are familiar with the material but if you are familiar with the material why are you reading the book?
I don't think this really needs any more research. Some malts will throw a haze and some won't. Further modification should fix the 'problem' otherwise do a protein rest. For most of us that isn't a big deal but remember that a mega wants the beer out the door at minimum cost, labor and capital expense. If they can skip one of the rests they can make more money.
I did also point out that it seems contradictory that a rest that supposedly does nothing to proteins is also thought to destroy the proteins responsible for head formation.
biertourist
Well-Known Member
Aj I trust your research, experience, and logic; I didn't mean to imply that you were literally "ignoring the brewing text"; I was just trying to give you a hard time (and use hyperbole to do it) and point out the humor in the thread which appeared to put you on the opposite side that you'd normally take. (Agreement with the literature, often in disagreement with home brewer observations.) -Electronic communication is so bad at getting that across much to my constant consternation...
Great to see MO specifically called out especially as it's supposed to be so highly modified AND has such a low DP (I'd normally roll out my "jump to conclusions mat" and assume that high modification also means that the proteins would have been broken down further than a less modified malt and that protein hazes would be less of a problem.)
Would it generally be safe to assume, as a general rule, that the less modified a malt is the more important that the protein rest is or is this too general of a rule and the total protein content would need to be factored in, too?
Adam
Obliviousbrew
Well-Known Member
As there is some literature saying that about protein rest there is some other (I´m sorry away from my computer until next week) that say the opposite. Name a hombrewer that never had chill haze issues... protein rest help me a lot getting clear beer and better head retation even with higly modified malts.
I knew that. I just wanted to be sure that I am not on record as saying you can ignore this work or that you must do a protein rest or that one isn't necessary.
I think the truth of the matter is the jury isn't in.
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