Mash temps and thickness VS efficiency and attenuation

[J A]

My accustomed mash schedule has been the same for a while. Lately, though, I've started looking at some tweaks.
I use a HERMS recirculating system and typically, I've done this:
- dough in at around .75 quarts per pound and hold at 122 for a protein rest of 15 minutes or so
- raise hot liquor temp and run enough into the mash tun to make the thickness about 1.25 quarts per pound and set mash temp to 148.5 for as long as an hour
- raise hot liquor temp and run enough into the mash tun to make the thickness about 1.5 quarts per pound and set mash temp to 158 and run for 15 to 20 minutes
- raise hot liquor temp and run enough into the mash tun to make the thickness 2 quarts per pound and set mash temp to 168 and run for 15-20 minutes for mash-out
- transfer contents of hot liquor vessel, which is also HERMS vessel, (usually around 180 degrees) to auxiliary vessel for gravity sparge and run wort collection at a rate of 2-4 minutes per gallon of wort collected.

When I got back into brewing last winter after not doing it for a while, I wasn't hitting efficiency numbers I was used to getting. Also attenuation seems a little low most of the time. Without changing too much, efficiency numbers have drifted back toward a higher range but I feel like I'm still missing a few points of attenuation. Yesterday I brewed my Cream Ale (15% corn) and tried to make a few adjustments to start tracking efficiency and performance.

I started by changing the mash thickness ratios and tweaking temps a little. I like the thicker mash for Beta rest but I wonder if I'm not losing some conversion efficiency with the combination of recirculation and relatively thick mash. I wanted to keep more active mash liquor in contact with the starches so I raised the Beta rest thickness to a little over 1.4 quarts per pound of grain. I also raised the temp slightly - a setting of 149.5 makes the temp swing from 148.5 to 150.5 or so. I also started raising the temp setting after a half hour so I was up at 152 or more after an hour.

From there I raised for a short Alpha rest as usual, also with a slightly thinner mash than I've used in the past and my usual mash-out procedure, though I made sure to raise the HLT temp to around 180 before bringing the water over to the mash tun. That raised the grain bed temp better for mash out.

For the sparge I set a slow flow and let it run. It turned out to be a little slower than usual and I didn't bother changing it. It must have taken an hour and a half to collect all the wort in the tun. The result was not only very high conversion efficiency but slightly higher wort volume. Making the bed to drain very slowly allowed more liquid to seep off - usually there's a big puddle in the bottom of the "empty" mash tun after it sits for a half hour or more before I get around to cleaning it out. I know from a number of brews that if I sparge very quickly, my efficiency goes down. If I run nice and slow, I get good efficiency and the wort is dead clear going into the boil kettle.

When it was all said and done with yesterday's brew, I had slightly higher wort volume than usual and the efficiency was 92%. I'll be very eager to see what happens with attenuation on this batch. I'm using Apex Berlin Lager yeast and fermenting at around 60F. That yeast is usually pretty good about attenuating - 80% is usually minimum. It'll be interesting to see whether my looser, higher temp Beta rest will get me some more fermentable sugars. The corn in the mix should dry things out a little so I'm hoping that I'll see as much as 85% attenuation.

PS...I'm not addressing Mash pH here...that seems like fairly well settled subject and one should pay attention to pH in order to get consistently good results. I typically add Acidulated Malt to the grain bill to get a mash pH that's in a good range according to the Recipe Calculator and I acidify sparge water to approximately 5.4 pH.

Moving forward I'll keep working with the mash thickness and temps to see if I can identify any trends. Any thoughts on this?

 

[dmtaylor]

My first comment: This seems more complicated than it needs to be, like you are overthinking every detail. Sometimes deep thought is helpful, but other times it can cause you to lose focus, placing too much emphasis on things that don't matter, and not enough on the things that do.

Second, I don't think mash thickness normally has anything to do with anything, but... 0.75 qt/lb is awfully thick, yeesh. 0.85 qt/lb is about as low as I ever go, and that's only for huge 1.100+ SG beers where I plan to partigyle or double-batch sparge. The grain is barely wet at 0.75 qt/lb methinks, not great for enzymatic activity. I could be wrong, but I might not be wrong. Something to think about, not really a question but a comment.

Next: Runoff and/or sparge time shouldn't have much to do with anything. I can get 92% efficiency with a fast runoff. It depends mostly on the crush, and the temperatures, and the pH, which I see you've only brushed on so far. I wouldn't be aiming for sparge water pH 5.4. That might be too much acid. I'm not a fly sparger, I batch sparge, but... I dunno. Maybe I shouldn't comment further on this. All I know is, high efficiency is possible with faster brewing. Speed of runoff or sparge shouldn't make that big a difference.

My first question: Have you ever calibrated your mash thermometer by subjecting it to both ice water at 32 F and boiling water at whatever your boiling temperature is for your elevation above sea level (probably not exactly 212 F)? 99% of brewers respond "no, never". This could be a big part of your problem. If your mash steps are slightly cooler by a few degrees than you thought, the lack of gelatinization at "148.5" might actually be 146 F, and thus your grain is just kind of sitting there with few of its starches exposed for conversion. When you raised this up a degree to "149.5" maybe this really did make a significant enough difference for you to help conversion at that beta amylase step. I'm thinking, maybe you got lucky on this batch, and might not be so lucky on future batches. Maybe you need to raise this up another degree or two to provide extra assurance of proper gelatinization and conversion. And calibrate your thermometer so you know for sure whether "148.5" really is 148.5 F and not 146 F or 150 F or whatever else. I know for my mash thermometer, it reads a couple degrees too high on one end (ice vs. boiling, I don't remember which) but a couple degrees too cold on the other end, such that "in the middle" at mash temperatures, it's reasonably accurate. That's called luck. Some might not be so lucky, over-trusting their thermometers. Most people will say "well I checked it against another thermometer and they both read the same". Well that's nice, but... what do they read in ice water and boiling water? If they ain't accurate there, maybe it's just a coincidence that they're both off by the same amount at mash temperature, who knows. I mean.... if you're going to over-think stuff, let's really over-think!

Why don't you just keep things simple and do a single infusion at 154 F for an hour and call it good? Have you done this? What was the result?

Who crushes your malt? Do you have your own mill? How much flour do you see in the malt after it's milled? How many whole kernels? How many pieces is the average kernel broken into? I'll give my answers to these later / next time.

What size batches are you making? How many pounds in your average batch? What's your pre-boil and post-boil volume?

I thought I had more questions, but I forgot what they were. That's all I have for the moment. This should keep us busy for a bit.

 

[Dave Y]

Are you hitting your target gravity coming out of the mash / sparge?

Have you checked out https://www.brewersfriend.com/forum/threads/all-in-one-brewhouse-help-thread ? Yes, it's basic but practicing fundamentals helps. There are some good tips in the thread even if you're not using an all in one system. Other cool guy named Dave makes some good points too. Thick mashes don't flow or recirculate well.

92% is nothing to complain about, hopefully you took good notes on the process changes so you can easily replicate.

 

[J A]

I'll clarify...I'm not having any particular problem that needs solving. My system works very well and is digitally controlled and calibrated. I don't do simple, single infusions mashes and have produced many, many kegs of (if I may humbly submit) pro-quality and award-winning beer . Most brewers here will use simpler methods and/or simpler equipment - nothing wrong with that...just not the subject of this post.
I'm merely opening a conversation about some of the finer points of things like mash thickness, temp range, sparge time, etc, that, yes, do indeed have quite a bit to do with everything. I'm sure there will be a few who are willing and able to nerd out.

 

[Craigerrr]

You are a special breed of Beer Nerd @J A , I love it

 

[dmtaylor]

He and I must be different special breeds.

 

[Megary]

@JA
I think one of the joys of homebrewing is taking a deep dive in order to understand the finer points of the system and the method that each of us use to make tasty beer. There are a lot of means to that end, and those means won't be the same for everyone. Still, a worthy exercise in my opinion.

I can't speak to your situation because I BIAB. 2.5gal, single infusion, no sparge, fixed kettle size. I think it's fair to say that my way of brewing is pretty "simple". It's also fair to call it "practical". But...this way of brewing does present some challenges, especially with mash thickness. Because I'm locked into a fixed kettle, with a fixed boil-off, and a fixed grain absorption, I am constantly dealing with thinner or thicker mashes depending on the intended OG of the beer I'm brewing. Essentially, the bigger the beer, the thicker the mash, the worse the conversion. And vice versa. Nothing surprising, but it does take a lot of good notes (and some guesswork!) to design recipes on this "efficiency sliding scale".

Good luck on your mission.

 

[Dave Y]

I'm not having any particular problem that needs solving

I'm sayin' ... at 92% efficiency, it's' a pretty good indicator you have a handle on things.
I think the mash thickness discussion is worthy. When I was doing the traditional "all in one" system brewing, the mash ratios in most recipes didn't seem right to me and it took me a while to find the happy medium. Aaaaaand then I got more and better equipment, so more fine tuning and so on.

I like anything that will improve efficiency in the mash extraction, save time and effort in the process or produce something unique, well liked, etc.
I also have been focusing on neighbor friendly beers of late. I couldn't pour the rye pils fast enough a few days ago, which just reinforced my wanting to brew it again, probably next.

 

[Bigbre04]

@J A if you are hitting >85% efficiency thats awesome on a homebrew system. That being said, the additional rests and stuff really arent needed with modern grain. I dont really know my mash thickness and i am not sure what a HERMS system is, but on my setup i shoot for a 149 mash in temp for 1 hour with recirculation. I have to mash in twice, but thats the stupid system that i have. I have been hitting >85% with most recipes at this point.

Apex Berlin was not my favorite, but i only really gave it one try. So far my favorite from apex for a lager is Munich lager, but it is a little fruitier. I have been doing my standard golden lager on their augustinian lager yeast and it has been clean and nice so far. Highly recommend the spunding valves for lagers.

I generally shoot for ~5.3 for normal beers, 5.4 for dark beers ph wise. i toss phos in after the mash runs for a little bit so that i can get a decent sample for my ph meter.

 

[J A]

@J A if you are hitting >85% efficiency thats awesome on a homebrew system. That being said, the additional rests and stuff really arent needed with modern grain. I dont really know my mash thickness and i am not sure what a HERMS system is, but on my setup i shoot for a 149 mash in temp for 1 hour with recirculation. I have to mash in twice, but thats the stupid system that i have. I have been hitting >85% with most recipes at this point.

Apex Berlin was not my favorite, but i only really gave it one try. So far my favorite from apex for a lager is Munich lager, but it is a little fruitier. I have been doing my standard golden lager on their augustinian lager yeast and it has been clean and nice so far. Highly recommend the spunding valves for lagers.

I generally shoot for ~5.3 for normal beers, 5.4 for dark beers ph wise. i toss phos in after the mash runs for a little bit so that i can get a decent sample for my ph meter.

HERMS (Heat Exchange Recirculating Mash System) is a basic recirc set-up so that the mash liquor is pumped through a coil submerged in a separate, temp-controlled tank. I measure mash temp at the point where it exits the coil on the way back into the mash tun. Since the enzymes are in the mash liquid, that's the temp that determines which enzymes are activated or denatured, not the temperature of the grain itself. If I control for temp coming out of the tun and before it reaches the HERMS coil, it would drive the heating liquid much higher and I'd have several degrees warmer mash liquid than I want and Beta enzymes could be denatured.
Yes, 85% efficiency is plenty good so I have no complaints. I'm just playing around with tweaks to see if I can be really consistent and get the best results.

 

[HighVoltageMan!]

Your attenuation and your efficiency are obviously 2 different subjects and may or may not be related.

The mash thickness of .75 pounds of grain is very unusual, most are 1.5 quarts per pound or higher. There is thought out there that a thinner mash produces a more fermentable wort, but I really can't say whether or not it's true. I personally just stick with a 1.5 quart/pound for simplicity's sake. I step mash and that does affect efficiency. I can track my gravity and it increases with each step. 92% is way above the average home brewer, so I think you're good.

I know I'm bucking conventional wisdom, but unless the mash temperatures are really out of whack, the attenuation is more yeast dependent than dependent on the mash temperatures. If you mash in at 155 or higher, it does affect attenuation. But if you mash at 145 or 152F, the difference is really not that much, but it may be enough that you want to keep it low or high depending what you want. Beta amylase will denature at 150F and above, but it takes 10 minutes or so before it's gone. At those elevated temperatures, the beta amylase is working at it's fastest rate just before denaturing. Now if you use a London III yeast, 34/70 Lager yeast or a Belgian strain, the same exact wort will have very different attenuation rates.

As for the temperature accuracy, the calibration of ice water and boiling is only useful if you know the probe is linear. There no guarantee that the temperature offset at 32 or at boiling will be the same at mash temperatures. If you want to check the temperature accuracy of your probe, the multiple probe method in the mash at temperature is as good as any. Buying a high quality RTD is probably the best, but if it's off by a degree or two it's likely not a game changer.

 

[J A]

Your attenuation and your efficiency are obviously 2 different subjects and may or may not be related.

The mash thickness of .75 pounds of grain is very unusual, most are 1.5 quarts per pound or higher. There is thought out there that a thinner mash produces a more fermentable wort, but I really can't say whether or not it's true. I personally just stick with a 1.5 quart/pound for simplicity's sake. I step mash and that does affect efficiency. I can track my gravity and it increases with each step. 92% is way above the average home brewer, so I think you're good.

I know I'm bucking conventional wisdom, but unless the mash temperatures are really out of whack, the attenuation is more yeast dependent than dependent on the mash temperatures. If you mash in at 155 or higher, it does affect attenuation. But if you mash at 145 or 152F, the difference is really not that much, but it may be enough that you want to keep it low or high depending what you want. Beta amylase will denature at 150F and above, but it takes 10 minutes or so before it's gone. At those elevated temperatures, the beta amylase is working at it's fastest rate just before denaturing. Now if you use a London III yeast, 34/70 Lager yeast or a Belgian strain, the same exact wort will have very different attenuation rates.

As for the temperature accuracy, the calibration of ice water and boiling is only useful if you know the probe is linear. There no guarantee that the temperature offset at 32 or at boiling will be the same at mash temperatures. If you want to check the temperature accuracy of your probe, the multiple probe method in the mash at temperature is as good as any. Buying a high quality RTD is probably the best, but if it's off by a degree or two it's likely not a game changer.

The only time I'm using a .75 qt/lb mash thickness is at dough-in. I just let everything soak and soften a little while doing a short "protein rest" before I add water for the firs conversion rest. That's usually 148 or so and is at least 1.25 qt/lb thickness. I doubt that my initial rest is doing a lot given that modern malts don't need much in the way of protein conversion but I think it helps with initial gelatinization of the starches.

 

[Ozarks Mountain Brewery]

I have a different set up with a true herms and a lot is lost in pipes and hoses so I cant really say so much per pound, so I just go by 2" above the grain bed after all the hoses are filled up, on my web settings it equates to 2 per pound

 

[Ozarks Mountain Brewery]

as far as efficiency, here's a new one, I've always hit my numbers until I changed suppliers, then I'm short every brew day, so grain suppliers makes a difference

 

[J A]

I have a different set up with a true herms and a lot is lost in pipes and hoses so I cant really say so much per pound, so I just go by 2" above the grain bed after all the hoses are filled up, on my web settings it equates to 2 per pound

Yeah, I've started taking a closer look at what's not in contact with the grain. My tun and recirc system probably has "deadspace" in the coil and pump of around a half gallon. That has an impact on actual mash to water ratio in the tun but my vessels are relatively tall and narrow so at 1.5 quarts per pound in the system, I'm covering the grain by a couple of inches, at least.

 

[Ozarks Mountain Brewery]

I just had a water change, private well from the utility company where everything was tasting harsh all the sudden, I just dumped 10 gallons of my favorite red so this batch I mashed at 154/5 and did lose efficiency, more than expected

 

[J A]

I just had a water change, private well from the utility company where everything was tasting harsh all the sudden, I just dumped 10 gallons of my favorite red so this batch I mashed at 154/5 and did lose efficiency, more than expected

It would be tough to have to re-formulate based on completely different water. The city water here in Austin gets a bad algae/lake odor and flavor over the hot summer. Good filtration pretty much takes care of it but I don't think it's perfect, even with that. I've thought about doing some batches with distilled/RO water to see if there's any difference. Interesting about your efficiency. I wonder if you'll attenuate lower than usual based on more dextrin/less fermentable sugars.

 

[HighVoltageMan!]

I just had a water change, private well from the utility company where everything was tasting harsh all the sudden, I just dumped 10 gallons of my favorite red so this batch I mashed at 154/5 and did lose efficiency, more than expected

pH has an impact on conversion efficiency. Beta amylase works better at lower pH and alpha amylase works better at a higher pH. The compromise between the two is 5.4-5.6 (measured at room temperature). If the pH gets higher or lower than that range, efficiency suffers.

High pH also can cause the bitterness to become harsh.

 

[Ozarks Mountain Brewery]

pH has an impact on conversion efficiency. Beta amylase works better at lower pH and alpha amylase works better at a higher pH. The compromise between the two is 5.4-5.6 (measured at room temperature). If the pH gets higher or lower than that range, efficiency suffers.

High pH also can cause the bitterness to become harsh.

yes 2 years in a row I had this water tested then the I only use those readings, I don't trust my $10 ph meter, lesson learned lol

 

[Mont Y. Märzen]

Mash thickness definitely affects conversion efficiency, if not overall, at least with respect to time involved. See Braukaiser.com. Unfortunately, that site seems to be mostly down at the moment. (some old direct links work) But it is available on archive.org. Kai did experiments testing mash thickness and concluded thinner worts convert more readily. I can attest to this as well. I do BIAB and regularly mash about 3.5qts/# and I get 80% consistently. (brewhouse efficiency to fermenter, I always mash to 100% conversion confirmed by an iodine test.)

Another factor I can confirm that Kai tested was mill gap. For most malts, I crush via 2 passes down to .028 rather than the much larger .035–.045 that is ubiquitously recommended. That can cause a runoff issue in some cases for non-BIAB brewers, but Kai tested down to .024.

Temp and pH are the other two main factors which he also documented.

If you are getting 100% mash conversion, but a variable or lower efficiency than you expect to fermenter, then that is a result of not having your losses dialed-in properly, or measuring volumes with a low degree of accuracy. I find it takes 3–5 brews of meticulous volume measurements to dial-in a system, and that has to be redone any time you change parts of the system or your process that involve wort loss which doesn't make it to the fermenter. Most folks don't realize a small fraction of an inch vertical space in a kettle of standard diameter is a significant amount of liquid. Guesstimating can easily bounce your efficiency numbers around.

Another variable is the actual grain bill. I did lots of SMaSH batches early on, and found different grains have different absorption rates. I never compared those results to the malt specs with respect to moisture content, but I'm sure that has an effect. (as does crush size) This could even vary from batch to batch from the same maltster depending on how tightly they control their end product specs. Loss to grain absorption is not insignificant and why I squeeze the piss out of my bags. I can easily recover 3–4 qts vs. not squeezing at all. (gravity drain gets maybe 1qt, but takes forever—squeezing is faster.) Some commercial breweries employ a press-plate system for lautering. For multi-vessel homebrewers, that might be an equipment/process upgrade consideration.

Finally, I always do a mash-out to increase viscosity and rinse my grains with the bag raised. (I care not for denaturing enzymes, that happens shortly on the way to the boil anyway) A sparge step would of course cover that step, but for anyone who does full-volume brewing, I can say I regularly buy another 5sg points doing so. Otherwise, those sugars are just left behind clinging to the grain.