Any Real Science on the Effect of Crush on Extract Yield?

Homebrew Talk - Beer, Wine, Mead, & Cider Brewing Discussion Forum

Help Support Homebrew Talk - Beer, Wine, Mead, & Cider Brewing Discussion Forum:

This site may earn a commission from merchant affiliate links, including eBay, Amazon, and others.

Pilgarlic

Well-Known Member
Joined
Feb 22, 2010
Messages
1,327
Reaction score
151
Location
Tampa Bay
I wonder if anyone else has come across this article in the Journal of Industrial Brewing, Volume 11, Number 3, 2005: "Effects of Mashing Parameters on Mash β-Glucan, FAN and Soluble Extract Levels". The authors conclude, among other things, that crush has NO effect on extract yield so long as the kernel is broken, the mash is brought to gelatinization temps. and the mash is held for a sufficient time (sixty minutes). The article is a good read otherwise and I recommend it, but it sure suggests that all this obsession about crush and efficiency is a lot of anecdotal hot air, doesn't it? Can anyone offer any real scientific evidence refuting this? I'd like to see it. Meanwhile, I'm very happy with the crush I get from my hand-cranked Corona. BTW, I hope this thread doesn't become an indignant string of "well here's what happened to my numbers when I got my MM..." or "So and so says crush is critical to yield...). Those anecdotes and hearsay arguments have already been beaten to death. Any evidence? Studies? Data? Science?
 
Maybe you should have posted this in the debate forum. I have nothing scientific to say, just opinion. Looking forward to hearing the replies though.
 
I don't expect many replies. But I do hope that someone else has come across a study that's on point. I've looked for them and found few.
 
Pilgarlic,

Here's something you might like to read from Southern Cross University
ePublications@SCU titled, "Biochemical and molecular evaluation of quality for
malt and feed barley" I've read a few pages and it's pretty interesting. Maybe it will help you with your quest! Biochemical and molecular evaluation of quality for malt and feed barley

:mug:

EDIT: Around page 11 started getting my attention. YMMV
 
that crush has NO effect on extract yield so long as the kernel is broken, the mash is brought to gelatinization temps. and the mash is held for a sufficient time (sixty minutes).

This sentence fragment says it all to me. The crush has no effect on yield if the grain is held at mash temperature long enough. It takes time for the water to reach the center of the grain particles, time for conversion to occur, time to get the sugars back out of the grain particle and into solution. 60 minutes is an arbitrary amount of time. Poorer crush may take longer, really good crush much less. Doing BIAB, I see evidence of conversion in 15 minutes but I still allow it 60 minutes to get the most sugars I can from it. Am I wrong to give it that much time? I don't think so as I enjoy the process enough that I am willing to waste the extra half hour if it gets me good beer.
 
Download the Powerpoint Named Practical Milling for the Craft Brewer from http://www.brewingwithbriess.com/Malting101/Technical_Presentations.htm

Briess even looked at efficiency with unmilled grain! Anyway, the conclusion here was that for homebrewers the efficiency difference with almost any crush was very good. I think for homebrewer, the "Normal Grind" in the picture is typical.


Milling_Sieve_Analysis.jpg

Nomral_Grind_Sieve_Ratios.jpg
 
Interesting, passedpawn. The presentation didn't make clear what a "stirrer" mash is, vs a "manual" mash. It appears that, whatever a "stirrer" mash is, it made some difference.

As to grind or crush, on the Pilot mill, "normal" yielded no extract advantage over "coarse", and on the Lab Mill, "Fine" yielded no more extract than "Normal". This is corroboration for the conclusions of the study I cited, that crush makes no real difference, assuming gelatinization and an adequate sach rest.
 
Interesting, passedpawn. The presentation didn't make clear what a "stirrer" mash is, vs a "manual" mash. It appears that, whatever a "stirrer" mash is, it made some difference.

As to grind or crush, on the Pilot mill, "normal" yielded no extract advantage over "coarse", and on the Lab Mill, "Fine" yielded no more extract than "Normal". This is corroboration for the conclusions of the study I cited, that crush makes no real difference, assuming gelatinization and an adequate sach rest.

Right. It definitely corroborates your post.

It also flies in the face of many anecdotal stories here on HBT of bad crushes and poor efficiency,
 
This is making me wonder why the standard Congress match for measuring extract yield would specify a fine grind and why the spec sheets for the various grains show a different %extract for fine grind vs. coarse grind. (Check the online spec sheets from any of the maltsters.

The fine grind/coarse grind difference really makes me question the conclusions in the cited article.
 
This is making me wonder why the standard Congress match for measuring extract yield would specify a fine grind and why the spec sheets for the various grains show a different %extract for fine grind vs. coarse grind. (Check the online spec sheets from any of the maltsters.

The fine grind/coarse grind difference really makes me question the conclusions in the cited article.

But for well modified malt, the difference between the course grind and fine grind extraction shouldn't be more than 1-2%. That's not zero, but nor is it a particularly significant difference.

I haven't found any solid research on the effects of grind on mashing, but I have spent a lot of time doing controlled tests on extraction rates of coffee. The interesting thing there is that a good, even grind lets you get away with less effective agitation during steeping, and vice versa. In other words, you need to have either a good grind or good agitation.

I wonder if something similar is going on in mashing. With good recirculation and fluidity, perhaps grind isn't actually all that big of a deal. But, if you've got problems with segmenting in your mash, perhaps a fine grind can compensate. That would seem to explain both the data here (which fits with my anecdotal experience...I've never found grind to matter much, except in extreme cases) and the anecdotal evidence of massive bumps in efficiency when the new mill gets unboxed.

In any case, very interesting find Pilgarlic. Sorry I can't add more.
 
Not scientific evidence, but a real world example at least.
On a recent tour of The Great Lakes Brewery,
I asked about their grain milling. They said
They don't really 'mill' their malt. It is
Passed through rollers with 'needles' and
the grains are pierced rather than crushed.
For the most part, they stay intact. It helps with
clarity and other things as well.
Didn't ask about efficiency though.
 
bottlenose said:
I've used this as a reference in the past. Look for "mill gap experiments". At least for his system, the finer grind increased efficiency.

http://braukaiser.com/wiki/index.php?title=Effects_of_mash_parameters_on_fermentability_and_efficiency_in_single_infusion_mashing

Just watched a "Modern Marvels" on brewing, in it Coors explained their crush as "a fine powder comparable to common wheat flour used at home for cooking" which would mean very high efficiency meaning less malt meaning normal gravity, very little malt, beer.

Common sense tells you the smaller the particle the easier it is to absorb in water. The finer the crush the easier it is absorbed in water, but who wants 90%+ effeciency?? Lower the alcohol the more you can drink!
 
I like this discussion, this is some good info from brewing science and practice. In which he is talking about the grist, and specially how some breweries mill there grain.

stand-back-try-science.png


"The newest designs use hammer-milled grists that are very fine indeed. Their are reasons for using the most finely ground grist that can be processed with the equipment available. The finer the particles the faster they hydrate on mashing, the faster the pre-formed soluble substances dissolve and the faster the extract leaches from the particles during sparging. Furthermore the enzymes have more ready access to their substrates in thoroughly disrupted grists. The surface/volume ratio of material is larger the smaller and more numerous the particles into which it is divided and so a finely divided grist provides a larger surface area on which enzymes can act and across which substances can diffuse. To varying extents the particles will be previous, permitting enzymes, substrates and the products of hydrolysis to enter and leave. In practice, finer grinding gives grists that, up to a given 'degree of fineness', yield higher extracts. Finer grinding is less advantageous with better modified malts (this is the basis of the analytical fine-coarse extract difference determination), but it is beneficial with many (perhaps all) mash tun adjuncts."

Later on he mentions,
"More finely ground grists are converted more quickly, saccharify faster, give higher extracts and sometimes the worts obtained are more fermentable and less turbid."

"By using very fine grists the whole mashing process can be carried out more quickly and with better extract yields . The levels of TSN and FAN increase and, at least with some grists, levels of soluble B-glucans increase and worst viscosities increase. Sometimes the flavor of the beer produced is improved, perhaps because the shortened mashing times allow less poorly flavoured material to be extracted."

In short Narziss, seems to agree that a fine grind not only allows for easier extraction and faster hydrolysis of endosperm, but could also improve the FAN levels in beer which would mean better head formation, and could make a better tasting beer due to less tannin extraction and such. This is obviously a newer study I wonder which one is correct.

I would worry about what he says here, "Finer grinding is less advantageous with better modified malts (this is the basis of the analytical fine-coarse extract difference determination), but it is beneficial with many (perhaps all) mash tun adjuncts." Seems to go against what he is saying all along?????

:mug: I have never heard of milling with needles, very interesting.
 
This is all very interesting. I would say though that there is a big difference between one careful, precise experiment and a good scientific result. A good theory is based on many predictable , repeatable experiments. That may be what we have here, I'm not sure. While HBT users may lack laboratory conditions (speaking for myself) there is value in the crowd sourced results, though anecdotal.

I wonder if there is a difference to the brewer between fine and course in terms of ease of sparging. In other words, The whole kernel may convert 100% (or the coarsest grind) but will a conventional sparge produce an acceptable wort gravity?
 
This is all very interesting. I would say though that there is a big difference between one careful, precise experiment and a good scientific result. A good theory is based on many predictable , repeatable experiments. That may be what we have here, I'm not sure. While HBT users may lack laboratory conditions (speaking for myself) there is value in the crowd sourced results, though anecdotal.

I get your point. However, sometimes the "crowd" can have mass delusions. I.e., when I started brewing, transferring to secondaries was the state of the art.

I wonder if there is a difference to the brewer between fine and course in terms of ease of sparging. In other words, The whole kernel may convert 100% (or the coarsest grind) but will a conventional sparge produce an acceptable wort gravity?

This brings up the two contributors to the final brewhouse efficiency. Mash efficiency refers to only the conversion from starches to fermentable sugars. Lauter efficiency is the ability to get those fermentable sugars out of the grain (presumably through sparging). The combination of these two is the brewhouse efficiency, and is what most of us refer to as efficiency.

I'm not sure which of these are being addressed in those studies (I haven't looked, actually).
 
Northcalais40 said:
I wonder if there is a difference to the brewer between fine and course in terms of ease of sparging. In other words, The whole kernel may convert 100% (or the coarsest grind) but will a conventional sparge produce an acceptable wort gravity?

This was my thought after reading this thread as well. I understand an uncracked kernel of grain will convert given enough moisture present of adequate temperature of water. That's nice and all, but unless the converted sugars are soluble enough to pass through the husk walls it means nothing to us.

Plus it really boils down to scale. Home brewers are inefficient in one aspect or another. To compensate for this lack of technology compared to the breweries we have to look elsewhere. Instead of mash stirrers and continuous sparging we crack the grain a little finer to allow our batch sparge easier access to the sugars, easy in, easy out.

I just woke up I hope I'm making sense.
 
This was my thought after reading this thread as well. I understand an uncracked kernel of grain will convert given enough moisture present of adequate temperature of water. That's nice and all, but unless the converted sugars are soluble enough to pass through the husk walls it means nothing to us.

Hmm...I'm not sure I follow. What do you mean by soluble enough? Sugars are completely soluble at the temps/concentrations we're dealing with as brewers. In order to selectively "filter" sugars, you really need an osmotic barrier of some sort. Mechanical filtration (like by a grain husk) is too big by orders of magnitude.
 
KuntzBrewing said:
Just watched a "Modern Marvels" on brewing, in it Coors explained their crush as "a fine powder comparable to common wheat flour used at home for cooking" which would mean very high efficiency meaning less malt meaning normal gravity, very little malt, beer.

Common sense tells you the smaller the particle the easier it is to absorb in water. The finer the crush the easier it is absorbed in water, but who wants 90%+ effeciency?? Lower the alcohol the more you can drink!

Decreasing particle size should increase the enzyme accessibility to the starches. It also might improve water absorption and swelling which helps aide the enzymes in better efficiency. I have a starch assay in my lab that requires a starch swelling step before enzymatic digestion so maybe it is the same with malts where the starches can swell easier if finer milled.

This is all just my speculation but starch degrading enzymes work fairly quick so on the home brewing scale, a 60 min mash might be long enough to negate particle size impact on digestion rate.

I have experienced very poor efficiencies and fantastic efficiencies with the same mill so I wonder if other factors like pH, temps, and good homogeneity / stirring the mash are most important in comparison to the quality of the mill.
 
I really appreciate the thoughtful answers. I'm persuaded that the effect of crush on yield is much overstimated by many homebrewers. Now if only all of the "echo chamber" writers and "experts" would stop propounding what appears to be a myth, many brewers might redirect their efforts toward more meaningful mash parameters.
 
I wonder if other factors like pH, temps, and good homogeneity / stirring the mash are most important in comparison to the quality of the mill.

This reflects my own thoughts. I pay close attention to my mash chemistry, and I always get very good efficiency that is repeatable batch to batch, which makes me wonder if some of the anecdotal "evidence" on "bad crushes" comes from homebrewers who aren't careful with other steps in their process.
 
Great thread, interesting.

I'd bet the single biggest reason that "the crush" is attributed to having the largest impact on efficiency is because it's the most visible and apparent change.

I can't visibly tell when a mash is 5.2 pH or 5.8, or 152° versus 162°, or 5ppm Ca vs 50ppm.

Hence, the highly visible and most simple, plausible explanations stick.

IMO our sample size is way too small to contribute anything but anecdotal evidence. Even the great Kaiser's studies - extremely helpful, but not statistically convincing.
 
I really appreciate the thoughtful answers. I'm persuaded that the effect of crush on yield is much overstimated by many homebrewers. Now if only all of the "echo chamber" writers and "experts" would stop propounding what appears to be a myth, many brewers might redirect their efforts toward more meaningful mash parameters.

All due respect, but I don't think this is a fair statement. The numbers and ideas presented only speak to conversion efficiency, ie converting the starch to sugar in the mash.

Unless you can demonstrate a reasonable brewhouse efficiency with what most brewers would call a poor crush, you have not busted a myth.

This is a very interesting thing, and I don't mean to dismiss it. But I have the feeling that you are misinterpreting the information.
 
dwarven_stout said:
This reflects my own thoughts. I pay close attention to my mash chemistry, and I always get very good efficiency that is repeatable batch to batch, which makes me wonder if some of the anecdotal "evidence" on "bad crushes" comes from homebrewers who aren't careful with other steps in their process.

I was told by a pub brewer to throw out my hydrometer and replace it with a pH meter If I dialed in the mash pH I would hit my target gravity and wouldn't need a hydrometer. I was a bit skeptical about that advice but perhaps that is they key.
 
All due respect, but I don't think this is a fair statement. The numbers and ideas presented only speak to conversion efficiency, ie converting the starch to sugar in the mash.

Unless you can demonstrate a reasonable brewhouse efficiency with what most brewers would call a poor crush, you have not busted a myth.

This is a very interesting thing, and I don't mean to dismiss it. But I have the feeling that you are misinterpreting the information.

You're right in that I am addressing only the conversion myth. Thanks for the clarification, but, you don't think there's a general belief that crush is critical to conversion? I do.
 
You're right in that I am addressing only the conversion myth. Thanks for the clarification, but, you don't think there's a general belief that crush is critical to conversion? I do.

I do too.

This forum is chock full of experience and anecdote and tribal wisdom. Not much scientific method here (some, though). There are so many variables involved, and so few brewers who control them, so it's impossible to "prove" anything based on the stories here.

I think this is a good thread.
 
MalFet said:
Hmm...I'm not sure I follow. What do you mean by soluble enough? Sugars are completely soluble at the temps/concentrations we're dealing with as brewers. In order to selectively "filter" sugars, you really need an osmotic barrier of some sort. Mechanical filtration (like by a grain husk) is too big by orders of magnitude.

So your saying that if the sugar is fully converted inside an intact grain husk (which, just to be clear, we both agree can happen?), one would effectively be able to extract those sugars? I do believe that, but without mechanical (squeezing) involvement or or over sparging it would be much harder to do, wouldn't it?

If I have any energy when I get home today maybe I'll try a pound of crush and uncrushed and see what the first running would be of each. Again, I feel the crush helps extraction efficiency, and not conversion. I think we crush small(er) to help out with the overall lack of efficiency in our equipment.
 
I too have no problem with the crush not being important - as long as everything else is optimized.

A fine crush will speed up the process though. It will also result in a more homogeneous mash which might help a bit with minor pH issues. With a finer crush this should allow the mash pH to stabilize faster as the organic acids will be more uniformly released into the mash, rather then more gradually with a course crush.

Also, an "intact husk" is far from that. It has lots of cracks in it to allow relatively free flow of anything dissolved on the inside to move to the outside.

I find the idea of using a needle roller to pierce the grain very intriguing. Yes you might have to mash longer, but this might help to keep the embryo, and it oils and other flavor negative compounds, intact and on the inside of the husk. You also might get a more homogenous grain bed, would allow for a faster sparge. The more uniform (and bigger) the particle size, the faster you can have the flow rate without it becoming stuck. Any extra time spent with a longer mash might be offset with a faster sparge (assuming fly sparge)
 
So your saying that if the sugar is fully converted inside an intact grain husk (which, just to be clear, we both agree can happen?), one would effectively be able to extract those sugars? I do believe that, but without mechanical (squeezing) involvement or or over sparging it would be much harder to do, wouldn't it?

What you're talking about here isn't really an issue of solubility. If I understand you correctly, you're suggesting that an intact grain husk might prevent solublizded sugars on the inside of a husk from mixing with the water on the outside of it. Is that correct?

Grain husks are extremely permeable, and solutions will tend towards homogeneity over time thanks to Brownian motion. I can't imagine that a grain husk would prevent this in any meaningful degree, especially if there is any kind of agitation or recirculation. If this is a concern, a gentle stir once or twice throughout the process would completely mitigate it.

If I have any energy when I get home today maybe I'll try a pound of crush and uncrushed and see what the first running would be of each. Again, I feel the crush helps extraction efficiency, and not conversion. I think we crush small(er) to help out with the overall lack of efficiency in our equipment.

How does it help, though, specifically? Are you suggesting that coarsely crushed grain absorbs more water per pound than finely crushed grain? Or that coarse grain prevents adequate homogenization?

pjj2ba just articulated what I was trying to say better than I can. I don't doubt that people are seeing spikes in their numbers from better crushes, but my hunch is that a coarser crush is a problem only relative to other "problems" (poor agitation, too short a mash, stuck sparges, etc.). I buy my grain from all over the place and sometimes crush it myself. Regardless of the type of crush, though, my efficiency is very consistent. More importantly, I can "find" every point of gravity that I am losing into the kettle simply by measuring the water that didn't make it in.
 
MalFet said:
What you're talking about here isn't really an issue of solubility. If I understand you correctly, you're suggesting that an intact grain husk might prevent solublizded sugars on the inside of a husk from mixing with the water on the outside of it. Is that correct?

Grain husks are extremely permeable, and solutions will tend towards homogeneity over time thanks to Brownian motion. I can't imagine that a grain husk would prevent this in any meaningful degree, especially if there is any kind of agitation or recirculation. If this is a concern, a gentle stir once or twice throughout the process would completely mitigate it.

How does it help, though, specifically? Are you suggesting that coarsely crushed grain absorbs more water per pound than finely crushed grain? Or that coarse grain prevents adequate homogenization?

pjj2ba just articulated what I was trying to say better than I can. I don't doubt that people are seeing spikes in their numbers from better crushes, but my hunch is that a coarser crush is a problem only relative to other "problems" (poor agitation, too short a mash, stuck sparges, etc.). I buy my grain from all over the place and sometimes crush it myself. Regardless of the type of crush, though, my efficiency is very consistent. More importantly, I can "find" every point of gravity that I am losing into the kettle simply by measuring the water that didn't make it in.

I was simply taking some real world things that I've experienced and tried to explain them the best I could for the discussion. I have no scientific knowledge and it appears you are quite versed in the subject. Everything I said was pretty much assumption.

Still a new brewer trying to figure it all out still :)

I wanted to perform the test because (and I'm not trying to argue with you at all) I just can't see in my head that if you mashed a pound of crushed and uncrushed grain, you would end up with the same first running in gravity. Again, not arguing with you at all, I just can't seem to wrap my head around it.
 
I have only the experience of 420 batches to draw on. It tells me that crush does make a difference. I came to this conclusion by brewing multiple batches of the same recipe with all other variables remaining the same...even the same bags of grain.
 
I was simply taking some real world things that I've experienced and tried to explain them the best I could for the discussion. I have no scientific knowledge and it appears you are quite versed in the subject. Everything I said was pretty much assumption.

Still a new brewer trying to figure it all out still :)

I wanted to perform the test because (and I'm not trying to argue with you at all) I just can't see in my head that if you mashed a pound of crushed and uncrushed grain, you would end up with the same first running in gravity. Again, not arguing with you at all, I just can't seem to wrap my head around it.

Please do argue with me! That's the fun! :D

Anyway, I have absolutely no doubt that you would get different values between crushed and uncrushed grain...the experiments passedpawn linked seem to suggest that. The OP is asking about the difference between coarsely crushed and finely crushed. Whole kernels wouldn't work well.
 
You're right in that I am addressing only the conversion myth. Thanks for the clarification, but, you don't think there's a general belief that crush is critical to conversion? I do.

I do agree with this point, but I don't find it really relevant or helpful to me and the way I brew.

As I understand, the news here is that a coarse crush will convert in the mash, nearly as well as a fine crush. But the lautering process will never be as successful with a coarse crush as with a fine crush, provided a suitable lauter tun.
 
Calais, yes, mine was a pretty specific question. I meant it to be. I didn't really expect that everyone would find it interesting.
 
As I understand, the news here is that a coarse crush will convert in the mash, nearly as well as a fine crush. But the lautering process will never be as successful with a coarse crush as with a fine crush, provided a suitable lauter tun.

Never is a mighty strong word here, though. In my system, I get equivalent lauter efficiency for a coarse grind and a fine grind. That's anecdotal, of course, but it shows that generalizations about this kind of thing are tough to make.

More broadly, though, I don't really get the idea. Why would a coarser grind lauter less well? Are you saying that a coarsely grind grist absorbs more water than a finely ground grist?
 
Given that even well-modified malt has a CG/FG difference, I find it hard to come to any conclusion other than that grind makes a difference. Whether or not this is noticeable depends on how repeatable your efficiency is, or for that matter if you trust your OG measurements to 0.001.
 
Ditto. I think we should join the scientists and craftspeople to help work out the best practices for homebrewing. I will continue to mill my grain as per usual.

I don't think anyone is suggesting that you should stop milling. Neither the article referenced by the OP nor the data passedpawn posted indicated that that would work out well.
 
Just watched a "Modern Marvels" on brewing, in it Coors explained their crush as "a fine powder comparable to common wheat flour used at home for cooking" which would mean very high efficiency meaning less malt meaning normal gravity, very little malt, beer.

Common sense tells you the smaller the particle the easier it is to absorb in water. The finer the crush the easier it is absorbed in water, but who wants 90%+ effeciency?? Lower the alcohol the more you can drink!

Remember, the goal of a Coors/Miller/Budweiser is low production costs. Time is money so the less times spent in each stage of the brewing process the better. Finer crushes lead to speedier mash times. That is their goal with the fine crush/grind of their grains, speed.
 
Many brewers, when they experience an anomalously low efficiency or generally have inconsistent or low efficiency, assume (or are told by throngs of 'experienced' brewers here) that their efficiency problems are the result of a "poor crush". The obvious solution, then, is to spend money on a new, expensive mill. The studies offered here would suggest that new mill isn't a panacea, and that one might productively look to other aspects of their process before jumping to the conclusion that their problem is crush.

My approach is to crush my grain as fine as I can while maintaining a whole husk. To me, maintaining the whole husk is more important (to facilitate sparging) than the particle size of the crush (with its negligible effect on yield). I'm able to accomplish this just fine, thanks, with my hand cranked Corona corn mill!
 
Back
Top