Milling grain for BIAB

[loudmacleod]

A little background...I just started brewing in Jan 2023. So basically a The first beer was an extract kit my wife purchased. Since then, I have been using all grain using the brew in a bag (BIAB) method because it helps keep the amount of particulates down in my wort. And I've added hop baskets for the boil and dry hop as well, which is a marked improvement.

Anyway, up to now, most of my beers have been a bit more sessionable and light. So I thought it was time to ramp it up a bit. So I just cracked open my latest batch of beer (my 7th), which was a double IPA. Don't get me wrong - it tastes great - my best yet. But I have had enough beer in my ale trail to realize that this still seemed a bit lighter than the 8% ABV prediction from online calculators.

For every subsequent batch that I have brewed, I have tried to refine my methods in order to get repeatability in the future. So I record volumes, temperatures, gravity readings, etc., but have not really paid too close attention to OG/FG until now. When I actually did the math for this beer, it turned out to be 4.5% ABV, which was puzzling. I reached out to a new friend who owns a homebrew store and he said that BIAB is notoriously inefficient. So they recommend double milling the grain to help with conversion. Has anyone else run into this problem as well?

 

[RM-MN]

BIAB can be extremely efficient but you need to mill the grain properly to get that efficiency. Get a mill like this one and set it as tight as you can will still being able to turn the crank.

https://www.amazon.com/Cranking-Ope...toFckaF33GM28wzdQ65Hu75Q04UKlwfwaAjYzEALw_wcB
I set my brewing software to expect 90% efficiency and still overshoot the predicted OG.

 

[loudmacleod]

BIAB can be extremely efficient but you need to mill the grain properly to get that efficiency. Get a mill like this one and set it as tight as you can will still being able to turn the crank.

I set my brewing software to expect 90% efficiency and still overshoot the predicted OG.

Thank you for the suggestion on the mill. I am not sure if I am at a point where I want to start milling my own grain but will keep this in mind. I have also wondered if my old touch-top coffee grinder would do the trick, but I fear that a lack of repeatability could be problematic.

 

[mac_1103]

When I actually did the math for this beer, it turned out to be 4.5% ABV, which was puzzling.

So what was off? OG? FG? Both?

 

[doug293cz]

BIAB does not have to have lower efficiency than other methods, and depending on process, may actually have higher efficiency than some non-BIAB processes.

You need to understand a bit about the factors that influence efficiency to understand how BIAB stacks up against alternatives.

Mash efficiency - how much of the potential extract (sugars, proteins, plus other minor components) in the grain makes it into your boil kettle, is the product of conversion efficiency and lauter efficiency. Conversion efficiency is a measure of how much of the potential extract in the grain is actually created as real extract in the mash. Lauter efficiency is a measure of how much of the extract created in the mash makes it into the BK. Brewhouse efficiency is mash efficiency reduced by loss of extract (wort volume) that is left behind going from the BK to fermenter.

Conversion Efficiency = Extract Actually Created in Mash / Maximum Potential Extract of Grain.

Lauter Efficiency = Extract in Boil Kettle / Extract Actually Created in Mash

Mash Efficiency = Extract in Boil Kettle / Maximum Potential Extract of Grain
Mash Efficiency = Conversion Efficiency * Lauter Efficiency

Brewhouse Efficiency = Mash Efficiency * Volume in Fermenter / Post Boil Volume

The things that can reduce conversion efficiency are crush being too coarse for starch gelatinization to complete during the mash, mash time being too short for gelatinization and hydrolysis of the starch to complete, mash temp being way out of range (either high or low), and pH being way out of range (either high or low.)

Hydrolysis is the chemical reaction that chops up long starch chains into fermentable sugar and unfermentable dextrin. But before hydrolysis can occur, the starch chains need to be (at least partially) gelatinized, and complete hydrolysis requires complete gelatinization. This is where crush size can affect conversion efficiency. Small grits (fine crush) gelatinize faster than large grits (coarse crush), so finely crushed grain can complete gelatinization, and thus complete conversion, faster than coarsely crushed grain. Double crushing can give you a finer crush than single crushing.

But to know if finer crush will improve your efficiency, you have to know whether or not your conversion efficiency is significantly below 100%. If your crush and mash conditions already give you ~100% conversion, then a finer crush will not improve your efficiency. Incomplete conversion is however, a common situation for home brewers, and crush often helps.

Lauter efficiency is equal to 100% minus % of extract retained in the spent grain. The amount of extract retained in the spent grain is determined by the concentration of extract in the wort retained in the spent grain, and the volume of wort retained in the spent grain. Sparging (rinsing the spent grain with plain water) reduces the concentration of extract in the retained wort, thus improving lauter efficiency. Reducing the volume of wort retained in the spent grain (such as by squeezing the bag), is another way to improve lauter efficiency. Larger grain bills absorb and retain more wort so reduce lauter efficiency compared to smaller grain bills. The chart below shows how lauter efficiency changes based on sparge process (batch sparge only), grain absorption rate (gal/lb), and grain bill weight / pre-boil volume (10 lbs of grain and 6.5 gal pre-boil is equivalent to 20 lbs of grain and 13 gal pre-boil for lautering):

In order to determine whether your lower than expected mash efficiency is due to incomplete conversion, or inefficient lautering, you need to calculate the two factors that combine to determine mash efficiency. You need to know which (or maybe both) is low in order to know what to change in your process to improve things.

Adding a sparge will improve your lauter efficiency. Dunk sparging - placing the drained bag in a bucket of fresh water and stirring well - is a form of batch sparging. Draining the bag more completely, or squeezing the bag will also improve your lauter efficiency, as they reduce the grain absorption rate.

If you collect the following data, you can do the calculations to determine both conversion and lauter efficiency:

• Grain Bill Weight
• Weighted Average Grain Potential (points per pound, or %) - 37 pts/lb or 80% can be used as a rough estimate if you don't have detailed potentials for all of your grains
• Strike Water Volume (the water volume for mashing)
• Pre-Boil SG
• Pre-Boil Volume
• Post-Boil SG and Volume can be substituted for Pre-Boil, but you can't mix Pre and Post data

If you can post the above data for one or two of your brew sessions, I can calculate the conversion and lauter efficiencies you actually achieved, and give you some guidance on what changes can improve your efficiencies.

Brew on

 

[Bobby_M]

It's a little dramatic to say "notoriously inefficient". Expect about 70-75% mash efficiency if you have the grain double crushed and give the bag a decent squeeze. What it DOES mean is that you can't just take a recipe kit or blindly follow ANY recipe you happen to find. The process goes like this:

Find a recipe
Carefully read the recipe's assumed mash efficiency
If it's 80%, increase all the grain amounts by about 10% and buy that.
Brew, check OG.... adjust for the next batch.

 

[loudmacleod]

So what was off? OG? FG? Both?

The OG was off

 

[loudmacleod]

It's a little dramatic to say "notoriously inefficient". Expect about 70-75% mash efficiency if you have the grain double crushed and give the bag a decent squeeze. What it DOES mean is that you can't just take a recipe kit or blindly follow ANY recipe you happen to find. The process goes like this:

Find a recipe
Carefully read the recipe's assumed mash efficiency
If it's 80%, increase all the grain amounts by about 10% and buy that.
Brew, check OG.... adjust for the next batch.

Thanks for the suggestions. Definitely learning a lot!

 

[Miraculix]

It's a little dramatic to say "notoriously inefficient". Expect about 70-75% mash efficiency if you have the grain double crushed and give the bag a decent squeeze. What it DOES mean is that you can't just take a recipe kit or blindly follow ANY recipe you happen to find. The process goes like this:

Find a recipe
Carefully read the recipe's assumed mash efficiency
If it's 80%, increase all the grain amounts by about 10% and buy that.
Brew, check OG.... adjust for the next batch.

I always had efficiencies at least in the 80s, if not in the 90s, when the grain was crushed sufficiently fine with full volume biab. If you're below 80% , there are process issues or insufficiently crushes grains.

 

[k-daddy]

I always had efficiencies at least in the 80s, if not in the 90s, when the grain was crushed sufficiently fine with full volume biab. If you're below 80% , there are process issues or insufficiently crushes grains.

Wow… that’s efficient! I do full volume BIAB with a somewhat fine crush (.028) and have never seen efficiencies anywhere close to the 80-90’s. My “no squeeze” process yields around 68% and, with a good squeeze, low to mid 70’s. I recirculate the mash and have run into stuck mash problems if I crush much finer. On recipes using flaked adjuncts, I now add them (after thoroughly mixing the other grains) on top of the mash so they’re not layered in from top to bottom. In the future, I might try to tighten my gap setting a few thousands to see what happens but grain is fairly cheap so chasing peak efficiency is not a top priority for me.

 

[Wigglebutts Brewery]

I agree with Bobby. If my beer is under 5% abv, I get about 75% efficiency. When the recipe approaches 6%; it’s closer to 70% efficiency.

 

[kurds_2408]

For sure listen to anything @doug293cz has to offer. He helped me work out some problems in my BIAB system and low efficiency earlier this year. I'm now getting 80-85% with a batch sparge. I would for sure get your grains double milled if not doing yourself.That's what I did before having my own mill and it helped. I now mill myself and only do one pass but I'm milling on like .025 of something like that.

 

[Bobby_M]

I always had efficiencies at least in the 80s, if not in the 90s, when the grain was crushed sufficiently fine with full volume biab. If you're below 80% , there are process issues or insufficiently crushes grains.

That's strange to me. Are we talking about full volume mashing or did you perform some kind of sparging process? That would matter a lot.

I full volume mash. I know exactly what's in my water because I build it from scratch. I know exactly how much water and wort I have at all times because I verified my volume markers are correct by weighing water first. I know exactly what my mash pH is. I weigh my grain out with a $400 commercial scale. I mill my grist to .018". I maintain exacting mash temperatures and run step mashes when the malt choices and beer style benefit from it. My mash/lauter efficiency, measured after separating the grain and wort is always between 68-75% mostly depending on target OG without fail. I've been brewing BIAB for about 8 years and almost all my local brewing friends brew BIAB and see the same numbers. It's probably more likely that anyone seeing 80% efficiency with BIAB has a measurement error somewhere. I'd upgrade that "probably" to "definitely" in the case of 90% unless a centrifuge is involved.

 

[Miraculix]

That's strange to me. Are we talking about full volume mashing or did you perform some kind of sparging process? That would matter a lot.

I full volume mash. I know exactly what's in my water because I build it from scratch. I know exactly how much water and wort I have at all times because I verified my volume markers are correct by weighing water first. I know exactly what my mash pH is. I weigh my grain out with a $400 commercial scale. I mill my grist to .018". I maintain exacting mash temperatures and run step mashes when the malt choices and beer style benefit from it. My mash/lauter efficiency, measured after separating the grain and wort is always between 68-75% mostly depending on target OG without fail. I've been brewing BIAB for about 8 years and almost all my local brewing friends brew BIAB and see the same numbers. It's probably more likely that anyone seeing 80% efficiency with BIAB has a measurement error somewhere. I'd upgrade that "probably" to "definitely" in the case of 90% unless a centrifuge is involved.

That's what I expected from you, that's why I was also scratching my head a little bit when I saw your efficiency numbers.

The only difference to my process is that I squeeze the bag as much as I can. If I'm doing bigger beers, let's say 1.06 and above, I usually squeeze the bag and then put is back into enough water to get a liquid state inside the bag, stir it and then squeeze it again.

That way my numbers are not dropping so much when increasing the og.

But obviously, even that way, the numbers get lower the higher the og gets.

How does your crush look like? Almost like flour? Because that's what's getting me my good numbers. With a more standard crush I get about 65%, maybe 70% if I'm lucky.

 

[Bobby_M]

That's what I expected from you, that's why I was also scratching my head a little bit when I saw your efficiency numbers.

The only difference to my process is that I squeeze the bag as much as I can. If I'm doing bigger beers, let's say 1.06 and above, I usually squeeze the bag and then put is back into enough water to get a liquid state inside the bag, stir it and then squeeze it again.

That way my numbers are not dropping so much when increasing the og.

But obviously, even that way, the numbers get lower the higher the og gets.

How does your crush look like? Almost like flour? Because that's what's getting me my good numbers. With a more standard crush I get about 65%, maybe 70% if I'm lucky.

.018" mill gap has a good deal of flour in it without completely shredding the husks and while I don't get a gym workout in while squeezing the bag, I shoot for a few liters of additional extraction that wouldn't otherwise drain out on its own. I definitely don't sparge.

 

[k-daddy]

.018" mill gap has a good deal of flour in it without completely shredding the husks and while I don't get a gym workout in while squeezing the bag, I shoot for a few liters of additional extraction that wouldn't otherwise drain out on its own. I definitely don't sparge.

Do you recirculate the mash in your custom BIAB setup at that .018 crush?

 

[Miraculix]

I

.018" mill gap has a good deal of flour in it without completely shredding the husks and while I don't get a gym workout in while squeezing the bag, I shoot for a few liters of additional extraction that wouldn't otherwise drain out on its own. I definitely don't sparge.

I also only sparge the strong beers. It involves another vessel and I'm lazy, so I try to avoid it.

I don't recirculate, I just stir the mash probably two or three times during the mashing.

What are the typical ogs of your beers? Mine are probably lower as I focus on English ales around 4.3% abv or so.

Still, I don't understand how your numbers can be that low tbh.

I even mash in my boil kettle so I'm topping off with some water after removing the grain because I don't have enough space in the pot. So technically it's not even really full volume what I'm doing.

 

[Zambezi Special]

I double mill, but that's more out of habit than necessity. My first brew came in at around 1.028 instead of 1.048 and I started double milling after that.

I have mash efficiency and brewhouse efficiency set to 73% and that works fine for my set up.
I brew small batches, but at high OG, to be diluted to required gravity. It fits my small set up, but is a bit unusual.

Whatever software you use, adjust the "standard" figures to your process. It doesn't really mattter if you get 70% or 85% as long as you know.
Obviously it is good to find out where your losses are, but at some point, just accept them

And now I am going to fully read and re-read @doug293cz post

 

[Exception13]

And now I am going to fully read and re-read @doug293cz post

I've read through it...and then re-read it. I missed the word "fully" though..... So I'm gonna go and "fully read and re-read".

To @Bobby_M 's point, though, I am doing full volume BIAB on one of his custom systems. I double crush to 0.02 (gonna tighten that up if I can), recirculate, and squeeze the bag enough to get a few extra litres out. Last brew was a Pilsner and my mash efficiency was 82% and Brewhouse was 62% as reported by Brewfather.

Now...to re-read (fully) @doug293cz 's post and see if I understand those numbers.

Cheers!

Chris

 

[Bobby_M]

Do you recirculate the mash in your custom BIAB setup at that .018 crush?

Yes. CAREFULLY at about 1 quart per minute. If I'm step mashing, I condition my malt to leave more intact husks and I can run the recirc faster during ramps.

 

[Miraculix]

Yes. CAREFULLY at about 1 quart per minute. If I'm step mashing, I condition my malt to leave more intact husks and I can run the recirc faster during ramps.

Maybe the conditioning is the issue here? I run my grains through a corona mill set as fine as possible (for the IKEA drill to handle), that gives me a lot of flour and the hulls are partly destroyed. But that's no problem with the bag I use.

 

[MikeCo]

I'm surprised to hear your mill gap is set at 0.018 inch. Mine is 0.030 and I thought that was small. I may have to experiment with narrower gaps.

 

[Shenanigans]

I

I also only sparge the strong beers. It involves another vessel and I'm lazy, so I try to avoid it.

I don't recirculate, I just stir the mash probably two or three times during the mashing.

What are the typical ogs of your beers? Mine are probably lower as I focus on English ales around 4.3% abv or so.

Still, I don't understand how your numbers can be that low tbh.

I even mash in my boil kettle so I'm topping off with some water after removing the grain because I don't have enough space in the pot. So technically it's not even really full volume what I'm doing.

Sounds like I have a similar BIAB system to you but I'm not getting those kinds of numbers either.
I actually never stir during the mash as I don't want to open up the pot and loose some heat but it might be worth the risk.
Have you noticed that stirring actually significantly improved the efficiency?
When do you do the first stir?

 

[kurds_2408]

Sounds like I have a similar BIAB system to you but I'm not getting those kinds of numbers either.
I actually never stir during the mash as I don't want to open up the pot and loose some heat but it might be worth the risk.
Have you noticed that stirring actually significantly improved the efficiency?
When do you do the first stir?

I stir mine at 15min. Thats when I take my ph sample so I like to give it a mix before taking the reading. I then leave it until its done but stir before pulling the bag.

 

[MaxStout]

BIAB can be extremely efficient but you need to mill the grain properly to get that efficiency. Get a mill like this one and set it as tight as you can will still being able to turn the crank.

https://www.amazon.com/Cranking-Ope...toFckaF33GM28wzdQ65Hu75Q04UKlwfwaAjYzEALw_wcB
I set my brewing software to expect 90% efficiency and still overshoot the predicted OG.

Nice.

I've been getting upper 70s to around 80 with a .030 gap. I have Beersmith set to 75, and I usually beat my predicted efficiency by a bit. I just tightened the mill rollers to .022 and will see what efficiencies I get going forward.

 

[Bobby_M]

Maybe the conditioning is the issue here? I run my grains through a corona mill set as fine as possible (for the IKEA drill to handle), that gives me a lot of flour and the hulls are partly destroyed. But that's no problem with the bag I use.

I doubt it. When I condition the malt, I end up with 80% fine flour but much more intact husks. I personally have no interest in chasing efficiency, especially at the cost of powdered husk material in the mash.

 

[Miraculix]

I never saw powdered husks. Only torn apart husks and I see no problem with that when using biab.

 

[hottpeper13]

I've got my mill set to .025 and condition the malt. It's a 3 roller fluted one and the husks come out almost completely intact. The oat malt ones look like day lilly flowers. I use a bag in my mash tun for larger batches or high gravity brews so I don't have to change the gap. For BIAB I get ~80% eff. with the sparging in the tun I get 86%.
The only thing that matters to me is knowing my efficiencies so I can adjust or design recipes foe my system. A pound of grain is less then a buck!

 

[Miraculix]

I've got my mill set to .025 and condition the malt. It's a 3 roller fluted one and the husks come out almost completely intact. The oat malt ones look like day lilly flowers. I use a bag in my mash tun for larger batches or high gravity brews so I don't have to change the gap. For BIAB I get ~80% eff. with the sparging in the tun I get 86%.
The only thing that matters to me is knowing my efficiencies so I can adjust or design recipes foe my system. A pound of grain is less then a buck!

With my limited space in the mash pot, efficiency dictates a bit the maximum ABV of my beer. I cannot do big volume mashes and boil it down, so I have to keep an eye on maxing out the efficiency as much as possible. Otherwise, I would agree with what you are saying. Just a bit different situations.

 

[AlcheMania]

A little background...I just started brewing in Jan 2023. So basically a The first beer was an extract kit my wife purchased. Since then, I have been using all grain using the brew in a bag (BIAB) method because it helps keep the amount of particulates down in my wort. And I've added hop baskets for the boil and dry hop as well, which is a marked improvement.

Anyway, up to now, most of my beers have been a bit more sessionable and light. So I thought it was time to ramp it up a bit. So I just cracked open my latest batch of beer (my 7th), which was a double IPA. Don't get me wrong - it tastes great - my best yet. But I have had enough beer in my ale trail to realize that this still seemed a bit lighter than the 8% ABV prediction from online calculators.

For every subsequent batch that I have brewed, I have tried to refine my methods in order to get repeatability in the future. So I record volumes, temperatures, gravity readings, etc., but have not really paid too close attention to OG/FG until now. When I actually did the math for this beer, it turned out to be 4.5% ABV, which was puzzling. I reached out to a new friend who owns a homebrew store and he said that BIAB is notoriously inefficient. So they recommend double milling the grain to help with conversion. Has anyone else run into this problem as well?

Mill tighter than usual. I just use a single pass. Even then i only get between 68 to 74% depending on base malt and mash schedule. Every recipe is gonna have to be dialed in after first go. Checking pre boil gravity is key for dialing in your calulations on subsequent batches.