How common is it to hit 90% mash efficiency with full volume/no sparge BIAB?

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lautzki

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Hi all,

According to Brewfather, I hit 90% mash efficiency at the end of my latest brew day. I exclusively do full volume/no sparge BIABs.

To me, this number sounds abnormally high given the fact most people are pulling around 70-80% mash efficiency using full volume BIAB. The question is: how common is this? My previous two batches have been varying around 69% to 76% of mash efficiency, and I'd rather have a consistent and predictable efficiency every single time. The only thing different in this batch was that I ordered the grain from another vendor who offered the option for a double crush (which I opted for) - apart from that, the process is the same. Can the difference be this dramatic when it comes to crush level?

FWIW, here is my process:

- I ordered the grain with a double crush.
- I heated 25 liters (6.6 gal) of mash water to strike temp, doughed in, hit 65c (149f) and kept it there for 60 minutes.
- I insulated the kettle by wrapping it in a reflective sleeping mat and a sleeping bag.
- I stirred every 15 minutes in hopes of increasing conversion and keeping temps uniform within the kettle. During the 60-minute period, I experienced a 0.5 Celsius degree drop in the mash temp, which I compensated by pulse heating the kettle back to 65c.
- After 60 minutes, I pulled out the grain bag, rested it on an oven rack that sat on top of the kettle, and I squeezed the bag using a kettle lid.

After the mash, I boiled for 30 minutes and here are the parameters that I ended up with:

Boil volume: 24 liters
Pre-boil gravity: 1.057
Post-boil kettle volume: 22 liters
Original gravity: 1.060
Grain absorption: 0.22 liters per kilogram
Boil-off: 4 liters per hour
Mash efficiency: 90.87%
Fermenter volume: 21 liters

And here's the grist:

76% 2-row - 3.6kg (7.94lbs)
15% Munich I - 0.7kg (1.5lbs)
7% Dextrin (Carapils) - 0.3kg (0.66lbs)
2% Caramel 30 - 0.1kg (0.22lbs)
Total: 4.7kg (10.36lbs)

Final gravity sits at 1.013 (estimate was 1.012).
 
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CascadesBrewer

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You might have gotten 90% with a good grain crush and squeeze. Do you feel like you have accurate measurements at all stages? I would note that the gravity points of your pre-boil and post-boil measurements do not quite match up. What temperature where the volume measurements taken at?
  • Pre-boil: 24L * 57 = 1368
  • Post-boil: 22L * 60 = 1320
Personally, I don't fully trust the volume and refractometer readings pre-boil and post-boil, but I am usually in the 78-80% mash efficiency and 73-75% overall efficiency (based on volume into the fermenter). My ultimate goal is gravity and volume into the fermenter, and mash efficiency is an early measurement to let me know if I am on track. I use the fermenter volume of cool wort and a hydrometer reading as my "true" measurements.
 
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jdauria

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Is it possible to get 90% mash efficiency, sure if you squeeze the heck out of the bag. But chances are just as good that either your volume reading was wrong or gravity reading was from a sample not mixed well. A couple times I got mash efficiency over 100% which is impossible, thus knowing I screwed up volume or gravity, or both.

To figure mash efficiency, you take the extract rating of grains times the number of lbs of grain/target batch size, then take pre-boil gravity number/the calculated number you get. So two row is 1.037 extract rating, Munich 1.034, Dextrin 1.033 and Caramel 30 1.035 per BeerSmith. So (37x7.94) + (33x1.5)+(35x0.22)+(33x0.66) comes out as 372.76. You say 21 liters into fermenter which is 5.55 gallons...so 372.76/5.55 = 67.16, so pre-boil gravity of 57/67.16 = a very good mash efficiency of 84.9%. However, if you are like many of us, then what you put in fermenter is usually greater than your target batch volume, so if your target batch was say 5 gallons, then it's 372.76/5 = 74.55, so 57/74.55 or a mash efficiency of 76.5%. Sorry, my American brain could not do this in kg and liters for you! ;)
 
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lautzki

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You might have gotten 90% with a good grain crush and squeeze. Do you feel like you have accurate measurements at all stages? I would note that the gravity points of your pre-boil and post-boil measurements do not quite match up. What temperature where the volume measurements taken at?
  • Pre-boil: 24L * 57 = 1368
  • Post-boil: 22L * 60 = 1320
Personally, I don't fully trust the volume and refractometer readings pre-boil and post-boil, but I am usually in the 78-80% mash efficiency and 73-75% overall efficiency (based on volume into the fermenter). My ultimate goal is gravity and volume into the fermenter, and mash efficiency is an early measurement to let me know if I am on track. I use the fermenter volume of cool wort and a hydrometer reading as my "true" measurements.
It is entirely possible that my volume measurements were off. My pre- and post-boil volumes were eyeballed using the stamped volume gauge inside my kettle, and final fermenter volume was also probably slightly off, as I use a FermZilla with a manually installed water level strip and the unit has a tendency to swivel around the metal stand it's been strapped to.

Pre-boil volume was hot, post-boil was chilled.

Is it possible to get 90% mash efficiency, sure if you squeeze the heck out of the bag. But chances are just as good that either your volume reading was wrong or gravity reading was from a sample not mixed well. A couple times I got mash efficiency over 100% which is impossible, thus knowing I screwed up volume or gravity, or both.

To figure mash efficiency, you take the extract rating of grains times the number of lbs of grain/target batch size, then take pre-boil gravity number/the calculated number you get. So two row is 1.037 extract rating, Munich 1.034, Dextrin 1.033 and Caramel 30 1.035 per BeerSmith. So (37x7.94) + (33x1.5)+(35x0.22)+(33x0.66) comes out as 372.76. You say 21 liters into fermenter which is 5.55 gallons...so 372.76/5.55 = 67.16, so pre-boil gravity of 57/67.16 = a very good mash efficiency of 84.9%. However, if you are like many of us, then what you put in fermenter is usually greater than your target batch volume, so if your target batch was say 5 gallons, then it's 372.76/5 = 74.55, so 57/74.55 or a mash efficiency of 76.5%. Sorry, my American brain could not do this in kg and liters for you! ;)
I was also thinking that my gravity readings might've been off as I used the ball valve tap at the bottom of my kettle to take both samples. I didn't really mix the wort well before doing that, so there might've been stratified sugars.

Thank you for the detailed calculation and explanation!
 

bracconiere

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During the 60-minute period, I experienced a 0.5 Celsius degree drop in the mash temp, which I compensated by pulse heating the kettle back to 65c.


i get 89% effec in beersmith's BH thingy....still good but with that comment, are you sure you didn't raise the temp to more then 65c? gel some more starch or something i get 89% all the time when i do a step mash at specific beta, alpha rests....? i fly sparge though, and decot, not cycle a element in the tun? and you say you were stiring often? i've always wondered why the second step at 162f gives me a effec boost, maybe the electric(?) element was gelling more starch, but not hot enough to denature alpha enzymes?
 

Miraculix

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i get 89% effec in beersmith's BH thingy....still good but with that comment, are you sure you didn't raise the temp to more then 65c? gel some more starch or something i get 89% all the time when i do a step mash at specific beta, alpha rests....? i fly sparge though, and decot, not cycle a element in the tun? and you say you were stiring often? i've always wondered why the second step at 162f gives me a effec boost, maybe the electric(?) element was gelling more starch, but not hot enough to denature alpha enzymes?
The high temp steps are getting more starches ready and denaturing enzymes at the same time, but the denaturation does not happen instantly. In fact, the higher temperature also speeds up the enzymes, so what's still left will work overtime to get these newly available starches chopped into sugary pieces
 

bracconiere

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The high temp steps are getting more starches ready and denaturing enzymes at the same time, but the denaturation does not happen instantly. In fact, the higher temperature also speeds up the enzymes, so what's still left will work overtime to get these newly available starches chopped into sugary pieces


honestly with my homemalt, that's what gave me the idea to get even decent effec with it...figured if after 15-30 minutes beta bit the dust anyway, mightest well milk the tougher alpha for more at 162f.....
 

Miraculix

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honestly with my homemalt, that's what gave me the idea to get even decent effec with it...figured if after 15-30 minutes beta bit the dust anyway, mightest well milk the tougher alpha for more at 162f.....
Beta ist not all gone by that point and the little that's still left goes rampage at that higher temperature, before eventually quitting for good.

And on the other hand you are completely correct with your "milking the alpha" idea. It just all happens simultaneously.
 

doug293cz

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Given your grain bill, strike volume and pre-boil volume, the highest possible mash efficiency obtainable is 86.34%, and this requires squeezing to a grain absorption rate of 0.315 L/kg (0.0377 gal/lb) which is a pretty aggressive squeeze. I adjusted your 24 L pre-boil volume (assumed measured at 65°C) to 23.52 L which would be the volume at 20°C. To get this mash efficiency, your conversion efficiency would have to be 100%, and the lauter efficiency would be 86.34%, and the pre-boil SG would be 1.050.

To hit 90.87% mash (and lauter) efficiency, you would have to have had a grain absorption rate of only 0.026 L/kg (0.0031 gal/lb), which is an impossibility for hand squeezing. Even at this efficiency, your pre-boil SG would only have been 1.053, vs. your measured 1.057.

Your volume and SG measurements are not self consistent. I feel confident in saying that you did not achieve 90+% mash efficiency, and that multiple measurement errors are responsible for this anomalous result.

All calculations above done using my mash and lauter simulation spreadsheet (which has been validated numerous times.)

Achieving 90% mash efficiency with a no-sparge process is extremely difficult, and can only be done with a low gravity beer (low grain wt to pre-boil volume ratio) and very aggressive squeeze to get a grain absorption rate below 0.04 gal/lb. See the chart below (mash efficiency only equals lauter efficiency if conversion efficiency is 100%, otherwise it is lower than lauter efficiency.)

Efficiency vs Grain to Pre-Boil Ratio for Various Sparge Counts.png


Brew on :mug:
 

bracconiere

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Even at this efficiency, your pre-boil SG would only have been 1.053, vs. your measured 1.057.

now for my own benefit i want to know how it was read, refrac, or hydro....and to that do you read the top of the gradient or bottom? and how important is being able to guess between something like 14 BRIX or 14.5? i punched it into beer smith wouldn't really matter to me but....
 

doug293cz

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now for my own benefit i want to know how it was read, refrac, or hydro....and to that do you read the top of the gradient or bottom? and how important is being able to guess between something like 14 BRIX or 14.5? i punched it into beer smith wouldn't really matter to me but....
Easiest way to explain a high SG reading is that the volumes were actually significantly less than thought.

Brew on :mug:
 

bracconiere

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Easiest way to explain a high SG reading is that the volumes were actually significantly less than thought.

Brew on :mug:


even a half gallon which is only 2/3" on my ruler, makes a big difference i learned a bit back.....and 'i guess' i could just look up wither you take the line or leave it for myself ;) :mug: and other things like how big it can get......

edit: i'd also want to say i always have crap luck with temp correction with hydros....always over states the gravity...
 

crazyjake19

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I've heard of people supposedly hitting 90%, but it seems like a stretch with full-volume, no-sparge BIAB.

I started around 67% using that setup, and after some tweaks to my Corona mill and my process I'm consistently 74-75% since then. Good enough for me, and I like the consistency.
 
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