Grain Crush Question

[hoppybrewster]

Everyone always talks about getting the crush just right. I've never understood why you couldn't just crush the crap out of it and sift out the hulls completely. No tannins and good efficiency? Someone tell me I'm crazy and why.

 

[TallDan]

Go ahead and try it, then post here about how to avoid a stuck mash.

 

[hoppybrewster]

Teach me about a stuck mash I've only done 2 all grain batches.

 

[doug293cz]

Everyone always talks about getting the crush just right. I've never understood why you couldn't just crush the crap out of it and sift out the hulls completely. No tannins and good efficiency? Someone tell me I'm crazy and why.

Leave the hulls, and control your mash and sparge pH to below 6. You will not have tannins. Read up about water chemistry and mash pH over in the Brew Science area of HBT.

Brew on

 

[wilserbrewer]

Hulls are needed for lautering. You wouldn't want to sift them out even if you could.

I think you are imagining removing the hills, and all that's left converts? Nice try, it doesn't work that way, all sorts of crap besides the sweet wort, proteins etc

 

[lhommedieu]

For batch sparging, the crushed husks keep the mash permeable to water and there is less chance of of a stuck sparge:

For continuous sparging, of "fly sparging," the crushed husks provide a filter bed for the gums, undissolved starches, proteins, etc.

Your crushed husks should comprise about 15% of the mass of your crushed grain. There is a recent discussion about grain crush here.

 

[outside92129]

And sometimes you want to add more husks! Rice hulls, especially when you have adjuncts such as corn, rice, and rye.

 

[Schol-R-LEA]

As the others have said, the hulls play a significant role in lautering. There are a lot of insoluble starches, gums, resins, etc. that won't dissolve even with a very tight crush, and without the hulls the result would be a sticky mess and a clogged lauter tun. If you ever try to brew with a hulless or thin-hulled malt like wheat or oat, you'll see what I mean. Recipes that call for a lot of wheat or corn generally require added hulls (usually rice hulls) to provide a looser grain bed.

Ideally, the crush for your malt should be just enough to crack open all of the kernels, but not tear the hulls apart entirely. The goal is to expose the soluble sugars and starches, but keep the hulls in place so that it forms a loose enough filter bed that the wort and sparge water can percolate through it. This is a large part of why roller mills are considered the best for brewing - they pull the grain through the rollers and compress it, but only the surface area that actually contacts the rollers is relatively small (compared to in a plate mill such as a Corona or Victoria, where the grain hulls contact the plate throughout the whole passage through the milling area).

 

[daksin]

Think about making bread- you add water to flour and it becomes dough. If you crush your barley into flour and add water, you have dough. Your starch will be converted but you will have an impossible to sparge mess. This forum (homebrewers in general, actually) make much too big a deal about grain crush. For the most part, once your grain is totally crushed and there are no intact kernels left, your efficiency barely changes (if at all) with crush fineness.

 

[hoppybrewster]

Think about making bread- you add water to flour and it becomes dough. If you crush your barley into flour and add water, you have dough. Your starch will be converted but you will have an impossible to sparge mess. This forum (homebrewers in general, actually) make much too big a deal about grain crush. For the most part, once your grain is totally crushed and there are no intact kernels left, your efficiency barely changes (if at all) with crush fineness.

Clearest answer yet, thanks

 

[Qhrumphf]

I would assume you also get some flavor out of the husks. In addition to all the other issues.

If you've ever brewed with substantial portions of wheat (which is huskless) in a grain bill you know how important having husks are.

 

[doug293cz]

For the most part, once your grain is totally crushed and there are no intact kernels left, your efficiency barely changes (if at all) with crush fineness.

There is a huge amount of anecdotal experience from BIAB'ers (reported on HBT) that says this is not the case. Do you have any evidence to offer besides just an assertion?

Brew on

 

[Qhrumphf]

I don't remember the details but i remember the relationship between mash efficiency and crush to be a curve. Conversion efficiency goes up as crush gets finer as the starches inside the kernel are fully accessible, up until the point where the crush gets fine enough that lautering efficiency goes down. The peak on that curve is towards the finer side, but not powder or flour.

Added complication is that as crush gets finer so does ratio of surface area of husk and so does tannin extraction (this is why crushing open husks and not shredding them or feathering them is ideal).

End point is that unless you have milling down to a science (wet milling or however it's properly called, and a perfectly tuned mill) to leave husks entirely intact but simultaneously expose all of the insides, then finer crush (within reason) yields higher efficiency.

My mill gap is set to 0.032", relatively fine, and I get ~98% conversion efficiency and 85% overall mash efficiency.

 

[doug293cz]

I don't remember the details but i remember the relationship between mash efficiency and crush to be a curve. Conversion efficiency goes up as crush gets finer as the starches inside the kernel are fully accessible, up until the point where the crush gets fine enough that lautering efficiency goes down. The peak on that curve is towards the finer side, but not powder or flour.

There should also be a relationship to mash time. Longer mashes should allow coarser crushes to more fully convert. The converse has been observed by several of our members who BIAB and crush extremely fine. They have found that they need to shorten their mash times, and mash at higher temps, to avoid overly fermentable wort. With BIAB, the potential for a stuck mash is greatly reduced (to the point of non-existance according to some, but I'm not quite there yet) so you can crush finer without adversely affecting lautering efficiency.

Added complication is that as crush gets finer so does ratio of surface area of husk and so does tannin extraction (this is why crushing open husks and not shredding them or feathering them is ideal).

Tannin extraction is also highly dependent on pH. In decoction mashes, husks are boiled without adverse tannin extraction. This can only happen because the pH is low enough to suppress tannin extraction. Keep your mash and sparge pH's low enough, and shredded husks shouldn't be an issue w.r.t. tannins. Shredded husks are likely to be less effective at preventing stuck mashes for those that don't do BIAB.

End point is that unless you have milling down to a science (wet milling or however it's properly called, and a perfectly tuned mill) to leave husks entirely intact but simultaneously expose all of the insides, then finer crush (within reason) yields higher efficiency.

Moistening grain before milling is usually referred to as "conditioning" the grain, and does lead to more intact husks after milling.

Anyone know of grain mills that employ smooth rollers. All the homebrew scale mills of which I am aware use knurled rollers, so that the drive roller will grab the grain, and the grain pulled by the drive roller will turn the non-driven roller. The knurling makes husk shredding worse. Smooth rollers would not tend to shred the husks as much, but both rollers would need to be driven, and the roll diameters would probably have to be larger to insure the grain gets grabbed and pulled thru the mill gap.

My mill gap is set to 0.032", relatively fine, and I get ~98% conversion efficiency and 85% overall mash efficiency.

I consider 0.032" a medium crush. I set my mill gap at 0.016" for BIAB, and many BIAB'ers (especially those with Corona mills) crush even finer than that.

Brew on

 

[wilserbrewer]

Anyone know of grain mills that employ smooth rollers.

I have seen a couple home built mills with smooth rollers. The "rub" is that the smooth roller needs to be around 4-6" diameter to grab the grain and feed. kinda surpasses the homebrew scale....but works super afaik.

 

[Qhrumphf]

There should also be a relationship to mash time. Longer mashes should allow coarser crushes to more fully convert. The converse has been observed by several of our members who BIAB and crush extremely fine. They have found that they need to shorten their mash times, and mash at higher temps, to avoid overly fermentable wort. With BIAB, the potential for a stuck mash is greatly reduced (to the point of non-existance according to some, but I'm not quite there yet) so you can crush finer without adversely affecting lautering efficiency........

.....I consider 0.032" a medium crush. I set my mill gap at 0.016" for BIAB, and many BIAB'ers (especially those with Corona mills) crush even finer than that.

Yep, BIAB can be crushed very, very fine. I've gone tighter than I do now, down to 0.028", but that made stuck mashes more common that I would like (as I use an MLT). Can't speak to the fermentability aspect, but that makes sense.

Tannin extraction is also highly dependent on pH. In decoction mashes, husks are boiled without adverse tannin extraction. This can only happen because the pH is low enough to suppress tannin extraction. Keep your mash and sparge pH's low enough, and shredded husks shouldn't be an issue w.r.t. tannins. Shredded husks are likely to be less effective at preventing stuck mashes for those that don't do BIAB.

There are plenty of factors on tannin extraction. pH is a big one, as is temp, and there are others too (not limited to grains). A little tannin is necessary, but it's when the combination of all these factors that push it into to much that it's a problem. If all your other factors are good, then some shredding likely isn't an issue, you're right. However, it's still something that if I can prevent it, I'd prefer to prevent it. Like everything else in brewing, there's often a tradeoff.

Moistening grain before milling is usually referred to as "conditioning" the grain, and does lead to more intact husks after milling.

Anyone know of grain mills that employ smooth rollers. All the homebrew scale mills of which I am aware use knurled rollers, so that the drive roller will grab the grain, and the grain pulled by the drive roller will turn the non-driven roller. The knurling makes husk shredding worse. Smooth rollers would not tend to shred the husks as much, but both rollers would need to be driven, and the roll diameters would probably have to be larger to insure the grain gets grabbed and pulled thru the mill gap.

"Conditioning" was the term for what I called "wet milling" that I was thinking of but couldn't put my finger on, thanks.

Come to think of it, the pro mills I've seen have been knurled as well, if I recall correctly (which I admittedly may not be recalling correctly).

 

[daksin]

There is a huge amount of anecdotal experience from BIAB'ers (reported on HBT) that says this is not the case. Do you have any evidence to offer besides just an assertion?

Brew on

I saw this talk given in person at the CCBA meeting a couple of years ago. Granted, this is for larger scale systems, but the physics at play are the same.

http://www.craftbrewersconference.com/wp-content/uploads/ImprovingBrewhouseEfficiency-Havig.pdf

Slide 26:All breweries with a VERY COARSE grind reported efficiencies greater than 89% No Breweries with a fine grind reported efficiencies over 89%

Slide 34: increasing particle size in case study improved efficiency by 1.5%

These improvements would be almost entirely due to increased lauter efficiency.

I would agree with some of the criticism that this really doesn't apply to BIAB, but I stand by the assertion that once your grain is totally crushed and your mash efficiency gets close to 100% (which it should be with a decent crush and pH control), particle size doesn't make much difference. Even with my BIAB, a larger particle size means sparging is much easier.

I might speculate that some of the BIABers who report greater efficiency with a very tight crush were getting lower mash efficiencies
(for various BIAB-related and unrelated reasons) and that decreasing particle size helped with that. Lauter efficiency isn't really a factor in BIAB.

 

[doug293cz]

I saw this talk given in person at the CCBA meeting a couple of years ago. Granted, this is for larger scale systems, but the physics at play are the same.

http://www.craftbrewersconference.com/wp-content/uploads/ImprovingBrewhouseEfficiency-Havig.pdf

Slide 26:All breweries with a VERY COARSE grind reported efficiencies greater than 89% No Breweries with a fine grind reported efficiencies over 89%

Slide 34: increasing particle size in case study improved efficiency by 1.5%

These improvements would be almost entirely due to increased lauter efficiency.

I would agree with some of the criticism that this really doesn't apply to BIAB, but I stand by the assertion that once your grain is totally crushed and your mash efficiency gets close to 100% (which it should be with a decent crush and pH control), particle size doesn't make much difference. Even with my BIAB, a larger particle size means sparging is much easier.

I might speculate that some of the BIABers who report greater efficiency with a very tight crush were getting lower mash efficiencies
(for various BIAB-related and unrelated reasons) and that decreasing particle size helped with that. Lauter efficiency isn't really a factor in BIAB.

The linked presentation uses different definitions of efficiency than what I normally see in homebrewing. Homebrewers typically use "brewhouse" efficiency as grain to fermenter efficiency, and "mash" efficiency as grain to boil kettle efficiency. The presentation uses brewhouse for grain to BK, and mash for grain to wort in mash. BrewersFriend defines efficiency this way: http://www.brewersfriend.com/brewing-efficiency-chart/. In this case "pre-boil" efficiency == "mash" efficiency. The typical usage among homebrewers is:

Conversion efficiency = % of potential sugar in the grain that actually gets created in the mash.
Lauter efficiency = % of sugar created in the mash that makes it into the boil kettle.
Mash efficiency = % of potential sugar in the grain that makes it into the boil kettle.
Mash efficiency = Conversion efficiency times Lauter efficiency.
Brewhouse efficiency = % of potential sugar that makes it into the fermenter.​

Brewhouse efficiency, as defined above, is not a good way to compare efficiencies because it is highly dependent on how much trub the brewer transfers to the fermenter vs. leaves in the BK.

Homebrewers should be able to achieve conversion efficiencies of 95% or better routinely. A large fraction of homebrewers reporting low efficiencies are not getting complete conversion. The cure for that is finer crush, longer mash and/or better pH control (not sure if pH just affects rate, or actual end point.) With BIAB, lautering is less of an issue, so finer crushes are often a good way to improve conversion efficiency, without having to spend more time brewing. For traditional lautering, at some point finer crush will start to interfere with lautering, so there is a limit on crush fineness for them. So, I think we are in basic agreement here, once we reconcile our efficiency definitions.

I don't know how to properly scale commercial scale lautering recommendations to homebrew scale. I would find studies done on 5 - 10 gal systems more useful. I would also like to see multiple brew sessions used for each efficiency data point. Small errors in volume measurements can lead errors in efficiency of several percent. A 1% or 2% gain based on a single brew session may just be noise.

What I found most interesting in the presentation was the assertion that excessive stirring leads to a more compact grain bed. This seems counter intuitive. Does anyone have an explanation of how stirring compacts a grain bed?

Brew on

 

[daksin]

The linked presentation uses different definitions of efficiency than what I normally see in homebrewing. Homebrewers typically use "brewhouse" efficiency as grain to fermenter efficiency, and "mash" efficiency as grain to boil kettle efficiency. The presentation uses brewhouse for grain to BK, and mash for grain to wort in mash. BrewersFriend defines efficiency this way: http://www.brewersfriend.com/brewing-efficiency-chart/. In this case "pre-boil" efficiency == "mash" efficiency. The typical usage among homebrewers is:

Conversion efficiency = % of potential sugar in the grain that actually gets created in the mash.
Lauter efficiency = % of sugar created in the mash that makes it into the boil kettle.
Mash efficiency = % of potential sugar in the grain that makes it into the boil kettle.
Mash efficiency = Conversion efficiency times Lauter efficiency.
Brewhouse efficiency = % of potential sugar that makes it into the fermenter.​

Brewhouse efficiency, as defined above, is not a good way to compare efficiencies because it is highly dependent on how much trub the brewer transfers to the fermenter vs. leaves in the BK.

Homebrewers should be able to achieve conversion efficiencies of 95% or better routinely. A large fraction of homebrewers reporting low efficiencies are not getting complete conversion. The cure for that is finer crush, longer mash and/or better pH control (not sure if pH just affects rate, or actual end point.) With BIAB, lautering is less of an issue, so finer crushes are often a good way to improve conversion efficiency, without having to spend more time brewing. For traditional lautering, at some point finer crush will start to interfere with lautering, so there is a limit on crush fineness for them. So, I think we are in basic agreement here, once we reconcile our efficiency definitions.

I don't know how to properly scale commercial scale lautering recommendations to homebrew scale. I would find studies done on 5 - 10 gal systems more useful. I would also like to see multiple brew sessions used for each efficiency data point. Small errors in volume measurements can lead errors in efficiency of several percent. A 1% or 2% gain based on a single brew session may just be noise.

What I found most interesting in the presentation was the assertion that excessive stirring leads to a more compact grain bed. This seems counter intuitive. Does anyone have an explanation of how stirring compacts a grain bed?

Brew on

Ah, you're definitely right about the terms- that's not helping anything. I was a little surprised about the stirring too. A bit of googling and poking around on probrewer suggests that, at least for a single-infusion mash (presumably of any size) that a fair amount of air is trapped in the grain/mash that provides some buoyancy to the particles or mash as a whole. Excessive stirring (particularly after the mash is complete) can shake this air out causing the grainbed to compact. I can't say if this is true or not, but our big mashes have fairly varied "compactness" so I may do some testing on the big system to see how mixing the mash affects lautering.