[brulosopher]

Brewers complaining of poor or inconsistent efficiency will likely be met with questions about their crush size, as it has come to be accepted that finer crushes have a positive impact on efficiency. However, many remain concerned that anything other than a coarse milled grist will ultimately lead to a beer with astringent and potentially other off flavors. We put this one to the test utilizing a method whose adopters commonly advocate for full-on grain pulverization-- Brew In A Bag. Did it make a difference? Results are in!

http://brulosophy.com/2015/11/23/mind-the-gap-course-vs-fine-crush-exbeeriment-results/

[kramerog]

The lower FG on the finer crush seems intuitive to me although I would not have predicted it before the experiment. By grinding the malt into flour, the starches are more quickly exposed to the enzymes resulting in more attenuation. 

[erockrph]

Were the tasters asked specifically whether they noted any astringency? That's always been the biggest alleged downside of a fine crush - that you create astringency by shredding the husks.

Regardless, since the majority of tasters preferred the fine crush, I think that validates my practice a bit. I'm wondering how much attenuation played into the taster's preference, however.

[brulosopher]

Were the tasters asked specifically whether they noted any astringency? That's always been the biggest alleged downside of a fine crush - that you create astringency by shredding the husks.

Regardless, since the majority of tasters preferred the fine crush, I think that validates my practice a bit. I'm wondering how much attenuation played into the taster's preference, however.

Tasters aren't ever asked such specific questions, rather those who are correct in the triangle proceed to a very brief comparative evaluation where they're asked about to select the sample they preferred as well as to guess which one the variable was manipulated on. The thinking here is that if we can get enough data demonstrating a certain variable creates a distinguishable difference, we'll return and do just a comparative brew since we can trust the difference is "real," if you will.

[brewinhard]

Plus astringency most likely comes from pH rise in the mash as untreated sparge water rinses away the "buffers" from the grist and mash.  The BIAB (like a no-sparge) process can lower efficiencies but greatly reduces the chances of tannins being extracted from the grains/husks.  But, I too would've liked this question asked specificially.

[dmtaylor]

Hmm.  This xBmt seems to me to be anomalous in some ways, yet at the same time, kind of as expected:

First, I think there could have been a yeast problem.  I see that the same yeast strain was selected for each batch; however, the same yeast starter was NOT used for each.  This creates an additional unresolved variable.  If one batch was not as healthy, or if one was contaminated, (or both?), this could explain part or all of the attenuation difference.

I also question how 19.75 lb grain could result in only 1.080 for 5 gallons with a standard mill gap setting.  This... just seems like a poor mash or crush somehow somewhere.  I recognize there's no sparge going on; however, I also can't help but challenge: just what percent efficiency was this, anyway?  Less than 50?!  I could be wrong but I believe most folks should be able to hit at least 50-55% brewhouse efficiency with no-sparge, with a standard mill gap quality crush.  Maybe not, but that's the impression I get.  I don't think this batch even hits 50% efficiency, but again I could be wrong and I have not run detailed calculations on it.  Anyway, along with this...

By the picture, that just doesn't seem to me like a 0.039" gap quality crush, although I have no objective basis for saying so.  Just doesn't *seem* right visually, based on my experience with my Barley Crusher.  Maybe the mill gap was just a little off, and actually 0.045 or whatever?  To be fair, the photographs might not be telling the whole story either.  But if the true mill gap was not really known, then perhaps it would be better just to say "we don't really know what it was", and thus avoid any questions like this.

I might also mention: if your mill gap is relatively wide, then of course your beer is likely to be lighter and lower gravity than when it's set real tight.  There's no shocker there at all.  In the first case, the hulls are pretty well intact.  In the second, they're pretty well pulverized and freed up more to darken the wort/beer. 

A more interesting experiment to me personally might have been to aim to achieve almost exactly the same original gravity with each beer (e.g., 1.090 with 50% efficiency, and then 1.090 again with 60% efficiency).  Obviously that didn't happen.  But then you could actually eliminate the variable of OG and compare beers having more equivalent general color and body.  Maybe another xBmt for another time!?  Might not been the intent of this one, but maybe another time.  It's one I want to run someday if I ever get a Round Tuit.

I have nothing but love for Brulosophy, but I also do see some xBmts better designed and documented than others.  And that's fine.  Please accept any and all criticism for the 2 cents it's worth.

One thing I can say: Even if all my other comments above are all wet, I can see one viable theory for a real explanation for the attenuation difference:

Reduced crush frees up fewer enzymes to convert yourn starches to sugars, as well as to break down said sugars from complex ones to more fermentable ones.  So, to achieve more similar beers, perhaps either a longer mash would have been necessary, or (of course) a harder crush.  In this fashion, the existing results are not terribly surprising to me.  Poor crush --> not so many enzymes knocked loose --> poor conversion --> poor attenuation, and vicy-versy.

[Whiskers]

Not totally clear on the ferm temp control - are the carboys individually controlled to 66degF for the duration? 

[ynotbrusum]

I think there is room to argue that there may have been some yeast differential here, but the test seems otherwise reasonably well conducted.  But a tablespoon of yeast nutrient?  That seems like a lot to add at that point and I wonder if that had a discernible difference/effect on the beers.  In other words is a less attenuated beer going to react differently to a late charge of yeast nutrient than a more fully attenuated beer and could it affect flavors/mouthfeel/other that would make discerning the different beer more easy?

[atodd]

I didn't see in the article but was the mash PH measured to see if the difference in crush affected it. 

I would also be curious how these beers would have looked without the use of Biofine. 

[crynski]

I am just reading and absorbing the discussion, but I have to ask, is there a pallet of Round Tuits in a warehouse next to that case of motivation I ordered years ago, and the buckets of elbow grease we sent the apprentice after?

Sent from my XT1254 using Tapatalk

[brulosopher]

Not totally clear on the ferm temp control - are the carboys individually controlled to 66degF for the duration?

Both pitched at 70F then placed in a freezer regulated to 66F, left for ~3 weeks.

I think there is room to argue that there may have been some yeast differential here, but the test seems otherwise reasonably well conducted.  But a tablespoon of yeast nutrient?  That seems like a lot to add at that point and I wonder if that had a discernible difference/effect on the beers.  In other words is a less attenuated beer going to react differently to a late charge of yeast nutrient than a more fully attenuated beer and could it affect flavors/mouthfeel/other that would make discerning the different beer more easy?

Both starters were produced from the same batch of wort and each pitched with 2 fresh pouches of 001 from the same lot. It could be a yeast issue, but I'm highly doubtful myself.

I didn't see in the article but was the mash PH measured to see if the difference in crush affected it. 

I would also be curious how these beers would have looked without the use of Biofine.

No pH measurements were taken, definitely next time!

I am just reading and absorbing the discussion, but I have to ask, is there a pallet of Round Tuits in a warehouse next to that case of motivation I ordered years ago, and the buckets of elbow grease we sent the apprentice after?

Sent from my XT1254 using Tapatalk

Cheers!

[Whiskers]

Both pitched at 70F then placed in a freezer regulated to 66F, left for ~3 weeks.

If it was the freezer and not the beer that was temp controlled, wouldn't the beers have fermented at different peak temperatures, both significantly over 66degF?  I checked a carboy once in a steady 67degF room and it peaked at well over 70degF - 73degF iirc.  Given this was glass and not a thin better bottle.  Beer of 1.065 or so. 
 

[dmtaylor]

I am just reading and absorbing the discussion, but I have to ask, is there a pallet of Round Tuits in a warehouse next to that case of motivation I ordered years ago, and the buckets of elbow grease we sent the apprentice after?

Sent from my XT1254 using Tapatalk

Not sure if I was blocked or just ignored.  Oh well.

Two different hydrometers were also used.  Were both calibrated?

[brulosopher]

Both pitched at 70F then placed in a freezer regulated to 66F, left for ~3 weeks.

If it was the freezer and not the beer that was temp controlled, wouldn't the beers have fermented at different peak temperatures, both significantly over 66degF?  I checked a carboy once in a steady 67degF room and it peaked at well over 70degF - 73degF iirc.  Given this was glass and not a thin better bottle.  Beer of 1.065 or so.

Placing the probe between the 2 carboys is a pretty common technique for controlling the temp of the fermenting beer. It's what I've been doing for years. I'm messing around with a BeerBug now and at 67˚F beer temp, the ambient temp waffles bewtween 56˚F and 65˚F.

[brulosopher]

I am just reading and absorbing the discussion, but I have to ask, is there a pallet of Round Tuits in a warehouse next to that case of motivation I ordered years ago, and the buckets of elbow grease we sent the apprentice after?

Sent from my XT1254 using Tapatalk

Not sure if I was blocked or just ignored.  Oh well.

Two different hydrometers were also used.  Were both calibrated?

Neither! I always appreciate your comments and thought they were mostly addressed in my other response. The hydrometers were both calibrated.