Author: Matt Waldron
When I started brewing about 3 years ago, I jumped right into all grain using 1 gallon kits then soon after bought a batch sparge setup with converted coolers for larger batches. I made many good beers, no doubt, but I found myself pining for a less complicated method, one that didn’t involve as much setup or clean-up but resulted in a finished product with similar quality. It wasn’t until a year or so later I learned about Brew In A Bag (BIAB) and, amid a run to win my homebrew club’s Homebrewer of the Year title, abruptly adopted it as my primary approach after buying a used e-BIAB system on a whim, sending me down a much simpler and less time consuming path.
As the popularity of BIAB continues to grow, and grow it certainly does, brewers are learning that particular variables, once accepted as convention, differ when using this modern approach. One such variable that has garnered quite a bit of attention lately is crush size, with the BIAB contingent contending the use of a fine mesh bag allows them to essentially pulverize their grain to the point of flour, much finer than the coarse grist required when fly sparging to ensure a proper lauter. Multiple anecdotal observations have demonstrated finer grinds seem to improve overall efficiency, a plus for those looking to get more out of their grain, but I still wondered– does crush size impact anything else?
| PURPOSE |
To evaluate the impact crush size has on 2 beers of the same recipe brewed separately with either fine or coarse milled grains and otherwise treated exactly the same.
| METHODS |
To make sure I got a solid look at all of the above mentioned aspects, I thought it best to go with a big Russian Imperial Stout, which was graciously provided by the fine folks at HomeBrewSupply.com.
Home Brew Supply Russian Imperial Stout
| Batch Size | Boil Time | IBU | SRM | OG | FG | ABV |
| 5 gal | 75 min | 85 | 60 | 1.080|1.090 SG | 1.028|1.020 SG | 9.2% |
Fermentables
| Name | Amount | % |
| Maris Otter | 16 lbs | 81 |
| Roasted Barley | 1 lbs 8 oz | 7.6 |
| Special B | 1 lbs | 5.1 |
| Crystal 60L | 12 oz | 3.8 |
| Chocolate Malt | 8 oz | 2.5 |
Hops
| Name | Amt/IBU (Tinseth) | Time | Use | Form | Alpha % |
| Magnum | 85 g/85 IBU | 75 min | Boil | Pellet | 11.6% |
Yeast
| Name | Lab | Attenuation | Ferm Temp |
| WLP001 California Ale Yeast | White Labs | 78% | 66°F |
The all-grain kits arrived well packaged with perfectly pre-measured grains to ensure both beers would be equal and fit for the xBmt.
Two days prior to brewing, I prepared separate starters of equal size and pitched each with 2 packs of WLP001 California Ale Yeast.
Both starters were crashed approximately 24 hours later in preparation to be decanted and pitched.
Due to time hampering circumstances, I brewed these batches approximately 8 hours apart. While the same exact equipment and processes were used for both batches, a concerted effort was made to ensure equality in all other areas.
I milled both sets of grain consecutively, starting with the coarse grist, running it through my 2-roller mill with a gap setting of 0.039 inches (1 mm), which cracks the hull and exposes the starch without completely demolishing the grain. This is a common default setting for many popular homebrew mills.
Once that was complete, it was time for me to mill the fine grist, but first I had to decrease the gap between the rollers. To do this, I loosened the appropriate roller and carefully moved it closer to the other roller, using a caliper to determine when they were approximately 0.025 inches (.5 mm) apart. My goal here was to essentialy pulverize the grains to a near flour-like state, something many BIAB brewers view as a luxury of their method since it is believed to improve their efficiency without any risk of a stuck sparge.
With both sets of grain ready to go, I set out to brew the first batch using the coarse grist. The mash held a steady 149°F/65°C for an hour before I collected the sweet wort and brought it to a boil. Hoping for a big, rich Imperial Stout, I was slightly disappointed when a hydrometer reading close to the end of the boil revealed the SG was lower than expected. To encourage a bit more evaporation, I added an additional 15 minutes to the length of the boil. Once complete, I quickly chilled the wort to 70°F/21°C and racked it to a sanitized fermentor before measuring the OG– 1.080. Substantially lower than the 1.100 I was hoping for. Oh well, it was getting late and I had some cleaning to do in preparation for the next morning’s brew. I pitched the yeast, shook the fermentor for 3 minutes, then placed it in my temp controlled fermentation chamber.
I returned early the following morning, approximately 8 hours later, to brew the fine crush batch. Second verse, same as the first. The mash temp was exactly the same and I made sure to adjust the boil length to 75 minutes. Following the chilling of the wort, I measured the OG and discovered the first objectively observable impact of crush size– this batch came in at 1.090. The 70°F/21°C wort was racked into an identical fermentor as the coarse crush batch, yeast was pitched, then I shook it for 3 minutes before popping it into the fermentation chamber.
Both beers took off quickly and were plugging along with seemingly similar vigor by the following morning. After 6 days in the chamber, both batches appeared to have calmed down, so I took a hydrometer measurement to see how things were going. What I observed suggested these beers might be taking different paths. The coarse crush beer was sitting at 1.030 SG and appeared visibly paler with less clarity than the fine crush beer, which had dropped to a much lower 1.021 SG. Interesting since the coarse crush batch got an 8 hour head start. I left the beers to finish up, ramping the temp a bit to encourage complete attenuation, then returned a week later for another check– no change.
A less stubborn brewer might have called it a day and packaged the beer. I am not that brewer. Rather, I added a tablespoon of yeast nutrient to each fermentor in hopes of driving the SG down a bit more, this led to a slight increase in airlock activity and bubbling on the surface of each beer. Since these beers had higher starting gravities, I let them sit in primary longer than I might with more coarse strength beers. At 29 days post-pitch, I took a final SG reading and found the coarse crush beer had dropped a smidge to 1.028 SG while the fine crush beer was at 1.020 SG.
It was at this point the beers were cold crashed, hit with some Biofine, then kegged and force carbonated. I allowed them to condition for about 2 weeks in my keezer before presenting them to participants. While both were looking good, there were some noticeable differences with the coarse crush beer appearing quite a bit lighter than the fine crush beer.
| RESULTS |
Forty-four people in total participated in this xBmt with representation from BJCP judges, experienced homebrewers, a few professional brewers, and craft beer drinkers. All of the data was collected in approximately 1 hour at the FIU Southern Brew Festival where I made sure to start early and stop before fest-goers imbibed too much. Each taster was served 2 samples of the coarse crush beer and 1 sample of the fine crush beer in colored opaque cups then instructed to identify the different one. To achieve statistical significance with this sample size, 20 people (p<0.05) would have had to make the accurate selection. All said and done, 24 tasters (p=0.001) correctly identified the fine crush beer as being different, providing support for the notion that crush size has an impact on more than just efficiency, but the ultimate characteristics of beer as well.
The participants who made the correct selection on the triangle test were then asked to complete a brief comparative evaluation. Out of the 24 respondents, 15 (62.5%) endorsed the fine crush beer as being the one they most preferred while 6 said the preferred the coarse crush beer and 3 said they had no particular preference. The same number of tasters responded correctly when asked to guess which batch was brewed using a finer crush, the other 6 wrongly choosing the coarse crush beer.
My Impressions: When presented these beers in a quasi-blind triangle, I was consistently able to distinguish them. I perceived the fine crush beer as having a fuller mouthfeel, greater complexity, and subtle alcohol twang in the finish. While my preference leaned toward the fine crush beer, the coarse crush sample certainly wasn’t bad! I experienced it as possessing a stronger roast character that was somewhat sharp and quite pleasant, although it came across much thinner than the fine crush beer and had qualities more consistent with Robust Porter than Russian Imperial Stout. In fact, I’ll be stowing a few bottles of the coarse crush beer away with plans to enter it as a Porter in a future competition. Either way, I was quite pleased with the recipe and would happily recommend the Home Brew Supply RIS kit to anyone looking to make this delicious style!
| DISCUSSION |
On the surface, it would appear crush size makes a difference, not only supporting the popular notion that a finer crush improves efficiency, but also produces a beer that’s reliably distinguishable from one made with coarser crushed grain. Cool, but some of the other data observed in this xBmt was unexpected and left me scratching my Movember stubble.
The fact the coarse crush beer had a lower OG than that of the fine crush beer yet finished with a higher FG was confounding to me. I would have at least expected both batches to be be within a similar attenuation range, but that didn’t happen, not by a long shot– the coarse crush batch was at 63% while the fine crush batch had a drastically higher 76% attenuation. Could this really be a function of crush size alone? In researching the topic, I discovered little in the way of prior investigation, though found a similar experiment done by Kai Troester on a lower OG beer. His results also showed that a finer crush did increase efficiency, but attenuation was noted to be independent of crush size. I kept digging and finally stumbled on a very old Brewer’s Journal research article that stated,
Of the different grades of grist, the fine meal takes longer to saccharify than the grits, but furnishes worts that attenuate further than those from the grits and husks.
I’m not sure what to think. I took every step possible to ensure both batches were treated equally in every respect except crush size, I even took measures to encourage the complete attenuation of both beers (nutrients, extended primary, etc.), and neither showed any signs of contamination. If the differences were caused by something other than the variable tested, I’m at a loss for what it might be.
It’s apparent our understanding of the impact crush size has on beer is quite limited and I look forward to learning more about this interesting variable. With the heaps of anecdotal observations combined with the slightly more objective data regarding crush size and efficiency, I’m comfortable saying a finer crush will likely increase one’s efficiency. However, given the paucity of research on this topic in general, I’d caution anyone from using this single point of data to justify a previously held belief or a change in process.
What has your experience with crush size been? Did you notice changes to anything other than efficiency when you changed your milling process? Please share your thoughts in the comments section below!
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59 thoughts on “exBEERiment | Grain Crush: Coarse vs. Fine In An Imperial Stout”
Now that’s a proper sample size.
It’s a large sample size, for sure.
Matt, do you have more info on your e-biab system? (specifically the controller, how big of an element to you use 120/220v, any issues with the bag contacting the element?)
Thanks,
I use a 5500W wave element that you can get at any Home Depot/Lowes, etc. for about $35-40. The trick for protection from it goes to a friend of mine that got a stainless steel 12″ pizza screen and use stainless seel bolts/nuts/washers to build “legs” for it to hold over the element. While you could adjust your brew bag length to fix this, I figure it is one more safeguard.
System is 220V. I don’t think for anything bigger than a 3-5 gallon total size I’d want to wait around for the boil using a 120V, even thought its easier. Compromise…can’t use the washer/dryer while brewing. (Oh darn.)
I used to ask my LHBS to double crush my grains, because everything I had read about BIAB said that was the way to do it. I never worried about efficiency enough to run numbers, I was happy with my simple system. The beer tasted fine, or so I thought. One day, I wondered why I hadn’t tried mashing a single crush batch to see if I could taste a difference between the two for myself. The difference was immediately noticeable. The beer was rounder, fuller, better tasting overall. I realized the double crushed grains were producing tannins in the finished beer, something that wasn’t supposed to happen according to all the BIAB info I had found online. I still like my simple system for half batches and never worry about efficiency, but my beer became significantly better after switching to the single crush.
Interesting, I did notice a better roast character in the regular crush beer and it would be interesting to see if that was just an effect on roasted grains (those above 60L without any diastatic power left in them.) TBH – if I was picking a size for myself, I might settle on something in-between. (I might widen to a .75mm gap a bit.) and see if there is a happy medium. If you get to make two of the same in a row, try it both ways and see how it turns out for you.
In true Brew-Do Voo-Do sense, it might be that each style should be dialed in a bit differently, but I think the efficiency and the very rich finished beer we got out the finer crush have shown me how to get one side of the style out…and I could steep some of the roasted barley/chocolate malt with a coarse crack to get the best of both world. But, that is just how you want to set up each VooDoo curse, er, brew day yourself.
The pH stabilizer is basically useless. I don’t know how much taste effect it had on this batch since it was used in both samples, but I wouldn’t count on it magically taking every batch of beer to 5.2. Lactic Acid and Baking Soda/Slaked Lime should be used if a certain pH is sought after.
Did you mash at too-high of a temp? What was your pH?
Mash went fine. Electronically controlled between 64-65 C, mash out too.
PH stabilized with MoreBeer’s 5.4 stabilizer in both batches.
So, both your temperature was too high & your pH was off – if you were getting tannins, that is. Because that’s what it takes to produce them – not just a finer crush.
This was supposed to be a reply to brewella deville – IDK why this response got placed here…
:[
That’s a common misconception, but all beer has tannins and their concentration can increase as a result of changes in a number of variables; including quantity and condition of husks. It’s best to think of tannin levels as a concentration that varies in every beer, not an on/off state.
Another great Exbeeriment leaving us readers with new questions and doubts. Thanks!
I wonder if all that roasted barley, chocolate malt and alcohol could hide other more subtle differences. I guess an average OG, low hopped beer (helles?) could reveal them if they exist.
I BIAB and I experimented a little with the mill gap calibration on my summer brewing. My limited and not scientific conclusion is that at some point the mash efficiency stopped climbing and the beer had some astringency that faded 4-5 weeks after bottling. All tests were done on ~1.050 OG pale ales.
Now I’m milling with a gap measured as credit card thickness (about 0.8 mm) and get constant 75-80% mash efficiency. I don’t find any affects on the final product with this gap and I’m very pleased with the efficiency.
Good points. I don’t think we should look at this xBmt as a suggestion for the “perfect mill gap setting” rather, what it was designed for — to see if the obviously fine vs. the standard coarse created a noticeable difference…which it did. We needed the extreme setting to be sure the crush variable came out, in other words.
I like your mill setting. It falls almost right between our two settings and may be on the road to answer the other questions – what is the “golden setting” with BIAB? And does that change with styles?
Your setting is similar to mine. I have it set so the credit card goes in but when the raised numbers bump up against the rollers it stops. I tested the setting with the hand crank not my cordless drill. Still not a 100% sure I have the setting in the correct spot though. I was lucky enough to get a peak at the mill setup at the Brew Gentlemen Beer Company in Braddock, PA and also compared my grist to a kit I purchased from NB that had the grains crushed already. My mark one eyeball says my gap is about 30% smaller than Brew Gentlemen’s and comparing my crushed carafoam grains to the kit, I feel I am narrower than theirs as well.
Has anyone conditioned their grains before? I read a brief article about it and may give it a go. The author said his efficiency jumped from the 60’s to the 70’s.
Interesting experiment. You should consider using the same hydrometer for both batches: it looks as though different hydrometers were used to test the two batches. That could introduce some error into the experiment.
Good point. I put them side by side to show same time, temp, etc. on the reading. Despite my new phones camera proving poorly suited to the task, I’ll have to ask you to take me at my word that I did more each sample in the other tube to confirm readings.
I have my gap set to 0.035″ right now but I’m thinking I should drop that down even lower. I use a BrewBag, so I essentially BIAB in a mash tun (MIAB, I guess).
Do you ever have any trouble with grain “dust” leeching though into the sweet wort? Sometimes I notice this grainy haze that comes through that I didn’t get when I did a more traditional false-bottom lauter.
I can’t say I ran into that, but this was a dark beer so I might not have seen it something like a grainy haze. I can tell you the coarse crush beer took longer to look clear (as was visible during tests.)
Here’s what a “finer crush” has done for me. I brew very small batches, sometimes just 2 gallons. We don’t drink that much and share… occasionally. Plus my back and feet problems makes lifting an issue. Every store I visit now does a fine crush. My last 3 gallon batch? I got five bottles out of it because of the sediment. The crush is so fine it passes through everything.
I’d rather just mash and not have to add all kinds of crud to the process, and to the wort, the ferm vessel, to accomodate this trend. I can adjust to get a fuller body.
I am getting my own mill soon. Have your “fine crush.” A gentle crack is my preference. And I admit: I’ve been brewing a LONG time, so I’m old school.
I hear you for the batch sizes. 5 gallons for holidays for when my family is in town but other than that, usually 2 to 2.5. Not that I can’t do it I just prefer not to have to carry 5 gallons of wort up and down my steps. My local brew store does a really fine crush. The guy was actually a bit perturbed at having so much grain dust around.
Could it potentially be an increase in the release of additional nutrients the yeasts enjoy? Maybe it more than the increased amount of available starch, extra FAN and other micro-nutrients released into the wort.
As well what did the trub levels look like in your fermenters between the coarse and fine batches? I have definitely noticed while dialing in my crush for BIAB that the finer I go the more trub I end up with in the bottom of my kettle and fermenters. Didn’t the exbeeriment for trub levels show higher trub levels generally causes slightly increased attenuation?
Great exbeeriment! The only thing that I can think of is that possibly the finer crush allowed for more access to the starches for the amylase enzymes during the mash, and therefore produced more fermentables than the coarse crush. Did the fine crush taste drier at all? This would be supporting evidence to the smaller sugars present. Just a thought.
I think Todd is right. I would add that maybe the larger crush actually need more mash time to for the enzymes to do all their work. You may have very quickly gotten all the starches out of the Crystal malts and roasted malts (which account for more of the unfermentable sugars), but not gotten all of the starches from your base malt. You ended up with a lower OG wort that was less fermentable and perhaps a longer mash (or more agitation/stirring during the mash) would have given you similar results to your fine crush batch, where the starches were quickly extracted and the enzyme reactions happened faster.
I also agree with Todd. Gelatinization, in particular, is a diffusion limited process that proceeds from the outside of the grits towards the centers. Smaller grits will gelatinize faster than larger grits, thus giving the amylase more time to work on the starch and (non-limit) dextrins, leading to higher total conversion, and more fermentable wort. A possible follow up exbeeriment would be to monitor the SG of the wort in the mash, and extend the mash time on the coarse crush until the SG matches that of the fine crush mash (which stays at the original 60 minutes.) You might need to cut the coarse mash off earlier than that if the time gets ridiculous.
I am definitely in the Fine Crush camp! I have a 1/2 BBL 3 vessel herms and recirc the whole mash period so I try to get my efficiency close to 85 -90% if I can! A fine crush does help with that. As I have said before I always use rice hulls too!. I think the crush is very dependent on your equipment and mashing method however. If you are BIAB and not recircing your mash I wouldn’t see why not go for full flour! However I do have a little Grainfather systme that I do my test batches on and it requires a much courser crush or the recirc will very slow or non existent. I always say getting a a few points under on your pre-boil wort is no problem as you can always add some DME and/or just Boil longer to get your numbers back in post boil!
I am in the fine crush camp. My Barley Crusher gap is set at 0.016″ (0.4 mm.) I do get lots of grain dust in my wort, even though I use a fine mesh polyester voile bag. It all settles out in the fermenter, and after gelatin fining, I get crystal clear beer. A two month old Octoberfest I brewed on this system (and employing Marshall’s fast lager method) just tied for first in category at a large local/regional competition, so you can make really good beers with non-traditional methods.
All of these experiments are great and something is learned in all of them. In this case though, I’m not sure we learned much about the effect of crush fineness. Unless I am missing something, the beers compared were 7.4% (course) vs 10% (fine) with large FG differences. People should be able to discern a difference between these beers. Most somewhat advanced brewers dial in their system and aim for a specific OG and FG based on their experience with efficiency, mash temp/time, pH, etc… In my opinion, in order to actually test differences in crush size, you would need to use the knowledge gained from this experiment to brew two beers with very similar OG, FG and ratio of grains, but with the two different crush types being the only difference. Just an idea for the future. Keep up the great work.
Yes, Joe, exactly! I want to know how the crush effects the taste of beers brewed targeting the same OG. So, I’m looking for the same XBmt but with grain amounts adjusted for efficiency differences caused by the crush.
Agreed as well. I initially assumed that this experiment was going to adjust/topup the wort so that they both started with the same OG.
Leaves room for a Mind The Gap – Part 2? 😉
Thanks for the post. It seems like since a high gravity beer can have a higher chance of fermentation problems that you would want to avoid them when making a comparison like this. They also tend to have a lower mash efficiency, a variable that we would expect to measure when testing crush differences.
Great experiment! Did you consider to mash longer(90min) due to the lower mashtemp?
Our LHBS in PDX had a low end limit of. 040 on their mill, something we stuck with all the whole scratching our heads at our low efficiency. We recently tried crushing to .037 and immediately noticed a 10% jump in efficiency after brewing the same recipe multiple times. We may push it lower still, but it’s good to see an experiment confirming what we suspected. Any thoughts on why the LHBS would limit crush size?
I’ve heard tighter gaps are harder on the rollers, my guess is they keep this in mind when setting it up.
Fair point. I was a little more insidious in thinking it was to cause people to buy more grain. What’s the tightest gap you use on a regular basis?
0.028″
Would .028″ be way too fine for fly sparge?
It depends on your setup. If you use a false bottom, it might be too fine, though I’ve never had an issue using a SS braided hose.
Good advice, thanks for the help. I’m currently looking at a different setup or potentially wrapping the false bottom in screen material.
Personally, I think it’s really important to remember that this was written in relation to BIAB brewing. The bag (in this case the super fine Brew Bag bag), acts as a super fine strainer so the fine crush has a different was of interacting. I would say with fly sparging, the old rules are the good rules — especially if you are not having efficiency problems. Fly sparging creates and even cascade through the grains that make their own filter bed for your lautering. In full volume BIAB you are stirring (a lot) all the way to the end to encourage all that grist to make contact and “give up the goods” then gushing the whole thing out in every possible direction from the bag. So, the fine grist helps create a “gushable” format for the grain bag system and the stirring encourages a lack of dough balls and dry spots your fly sparge handles with a different grain layout.
As to the “Tightest Gap” question — I don’t think I’d go lower than .5mm. It was near flower and my mill moved a LOT slower than it did at other times.
If it makes you feel any better, I have played with it a little. Not identical brews, but I have enough brews with both LHBS mill, double crushed at LHBS and my corona mill set tighter than a misers pocket book. All of this is BiaB over the last few years and some of those are on similar gravity beers with the same yeast strains.
With BiaB and LHBS I’d typically get 70-75% dipping as low as 63% for a really big beer. Double crushed would only improve that maybe 2-3 points, so I gave up the extra hassle of standing around crushing everything again. I didn’t practically notice an attenuation difference. Moving to my corona mill spitting out husks and fine flour my yield jumped to 76-83% with the couple of higher gravity beers (only a Tripple at 1.092 and a DIPL at 1.086) still hitting about 74-75%. I have also noticed that beers with the corona mill also tend to attenuate about 2-3 points further than with the dual roller LHBS crush. So beers that were attenuating 72-75% before are typically attenuating more like 74-78%.
I also like the character of my beers better. I noticed that, but I chalked it up more to playing with variety of having lots of bulk grain I can mill minutes before I start brewing. But, it could have a small bit to do with the finer crush and BiaB. Dunno.
Maybe my own “Confirmation Bias” creeping up here, but yours is one of many reports I’ve seen of BIAB brewers getting better results with a tweak in grain milling. I’ll keep exploring the topic as well as other BIAB tweaks, thanks for the info.
Sorry to resurrect but I brewed this weekend and, for whatever reason, after milling my grain it looked like steel cut oats. I’ve never crushed my grain this small. I chalk it up to talking with in laws while setting up for the brew day. That being said, the rest of the day went fine and amazingly, no stuck sparge. Unfortunately,I could not for the life of me get a clear vorlauf. I even added an extra gallon and sparged three times but to no avail.
To my point, I ended up getting a boatload of trub in my fermenter. But, after chilling to 64F and throwing in a packet of T-58, about 4 hours later, there was krausen and some wicked fermentation taking place. 24 hours later, it is unbelievable what’s going on in the carboy. I’m reminded of the “Kettle Trub xBMT”. Would a smaller gap lead to more trub thus leading to higher yield overall yield?
Huh, I tend to crush pretty fine myself and I haven’t noticed an issue with getting clear runoff out of the MLT.
I can only speak to the BIAB results…but the “more true = healthier beer” argument bears more research if time permits.
That’st he first time it’s been an issue for me. I always spread out the used grains around some trees so I took a few minutes to compared them. Definitely fewer identifiable husks than the other brews. Starting to worry about tannins now. I do have some new 5-gallon paint strainer bags from Lowes. I’m thinking about doing a BIAB for my next one. One interesting point, the color of the wort has changed from a very muddy amber to an almost golden hue and the fermentation is down by half. This is going to be an interesting batch.
Thanks for everything you guys do.
Hi Matt & all
Just found my way to this blog when looking at info about fermenting under CO2 pressure & natural carbonation in a corny. I really appreciate the depth of research & curiosity satisfaction! Moving up thru all the good comments & questions, here’s my $.02 – Before I bought my Barley Crusher a few years ago I wondered where to set rollers & reasoned “a bit finer” crush would be more efficient, so set them at .030″ / .75mm & did this test:
Two identical one-liter french press jars, 8 oz of same 2-row in each (one batch of grain fresh milled by LHBS that looked pretty course. The other 8 oz from what I just did with my new mill at 030″(was significantly finer). Poured same 160F water on both & put them in a warm oven for about an hour with a couple stirs. After that I actually use the french press plunger on both, then checked th SG of each “wort” sample after it cooled. Don’t remember the exact figures, but there was a substantial difference! ** Finer crush = Higher SG, Naturally **
As the finer ground pieces & flour are more accessible to the enzymes as others have commented.
I use a heatable mash tun on a burner with false bottom & circulate from the bottom with a simple March pump system. So I usually go thru two or more saccharifation steps “because I can”. I get very high mash efficiency, good conversion & never a problem with stuck mashes. Not surprising or confounding to me that this HIGHER SG wort ferments to a LOWER SG just like the quote you found:
“Of the different grades of grist, the fine meal takes longer to saccharify than the grits, but furnishes worts that attenuate further than those from the grits and husks.”
Keep up the great work! Just saw your whole list of blog & looking forward to reading them all! Q
Thanks for sharing. That sounds like a cool way to develop a sample relatively quickly. I will certainly be fine crushing/double crushing my BIAB going forward to help my efficiency (and my next xBmt looks even further at that) so keep an eye out here for more tips. Its good to know your results mirrored ours and had an angle that throws a bit more light out there.
Very interesting, although i find the beer choice to be suspect in the outcome. I would expect a light beer to truly understand the effects of fine crush, I.E. a Kolsch of a pilsner. as astringency in darker beers is somewhat a desired profile, and in a lighter beer would stand out like a sore thumb. I have done most anecdotal tests in this category but with lighter beers and found a substantial flavor profile difference, to support a course crush over a fine, whereas the fine crush was astringent as expected with a off flavor that i would describe as a twang.
Some of the other data could be perceived as this: the higher OG can theoretically be attributed to more particulate in the wort that would eventually settle out, Which may have been evident the the amount of trub difference between the two batches post fermentation.
The second bit of data that could be explained is albeit a stretch is the the fine crushed grains allow more possibility at the cellular level of the starch chains being destructed in such a way to allow more beta amylase via increased surface area. Just a thought.
I want to thank you for doing this exbeeriment I found it very well done and well written/documented.
Gary F
Gary,
Thanks for reading! I chose the big RIS as it would give us a stronger show of efficiency thanks to the pure power of a larger grain bill. A light, delicate beer might have been great for pointing out flaws (and, no reason not to run this xBmt again in the future with a Kolsch or other lighter recipe) but we also wanted to make sure there was enough room for a big range of movement in OG/FG from the recipe. Since I was not looking to have an imperial lager around, the RIS seemed like a great touch and the RIS recipe we went with is pretty straightforward.
Hope things are well up there in Main! Let me know if this helps your BIAB adventures in the future.
Great stuff! I might consider running this Exbmt and doing the triple blind or something like that through the brew club. I think you did establish without a doubt that you get a higher OG as expected. I can actually believe the lower FG in the fine crush, to me it makes sense, the question for me is flavor, People seem obsessed with efficiency, of the mash, i say Meh! i could care less if my mash eff is 67 or 77% as long as it is consistent and it produces a beer with little to no off flavor profiles, i find that more important. All in all thank you again for dooing this! also I just found this site and LOVE IT! Cheers No BIAB for me all grain 10 gallon RIMS
“I perceived the fine crush beer as having a fuller mouthfeel, greater complexity, and subtle alcohol twang in the finish. While my preference leaned toward the fine crush beer, the coarse crush sample certainly wasn’t bad! I experienced it as possessing a stronger roast character that was somewhat sharp and quite pleasant”
…What if you crushed the base malt/maris otter with a fine setting and used a medium/coarse setting with the specialty grains so you get the higher efficiency from the fine sample and still get the more robust/roasted flavor you reported from the coarse sample? Think that would work?
That might work. Darker grains have little/no diastatic (sp) power to them, so splitting out for effect could work. Let me know how it goes.
I do biaBasket, with the fine milling I was getting high 80’s efficiency so I tried course milling and got the same efficiency. The reason I think is mixing during and after the mash and sparging. I still get great efficiency and less gunk in the fermenter.
What was your efficiency? I plugged your numbers into BeerSmith and came up with 57% for the coarse crush and 64%b for the fine crush based on your recipe and results. It looks like you mashed at 147-149, but ended at 1.028 for the coarse crush and 1.024 for the fine crush. Based on your numbers, you got 57% attenuation for the coarse crush and 77% attenuation for the fine crush, although BeerSmith predicted you should get 1.015 for the fine crush with the mash temperature you seemed to have. Based on my experience, BeerSmith is only off by a point or two, even for big beers. It seems like both batches are under attenuated. Did you use pure oxygen for this? Did you add yeast nutrient?
I would be really interested to know if the widest setting on a flour mill would work alright for beer grains? If it’s about 50% flour and the hulls are a little cracked, will it still work?
Which feeler gauge do you use to measure you mill gaps? A lot of the ones I see only go up to .035 inch.
I think what may have happened is that the starch (and other stuff) extracted more quickly from the more finely crushed grain. Once it is extracted and dissolved in the water it is accessible to the enzymes that chop starches into sugars.
The coarser crushed grain puts starches into the water more slowly. This matters because the enzymes that chop it up are gradually destroyed by the heat, so more effectively chop to sugar the faster dissolved starch.
Both starch and sugar increase IG, and there’s more in the fine crush. Fermentation converts sugars but not starches, so the coarse crush, where there’s lower total carbohydrate but more of it is starch, winds up at a higher FG.
If this is correct, you may be able to vary the same sorts of things by temperature profile and mash time variation.