So I’ve done several brews in a bag and always seem to have an issue with beers stopping around 1.018-1.020, even a bitter I brewed recently and mashed at 151 with a starting gravity of 1.041. I mentioned it to another brewing friend the other day and he said, well, it could be that when you’re direct firing the kettle, down at the bottom of the mashtun, some of the enzymes could be denatured because it’s likely very much hotter on the bottom than it is in the rest of the mash. Even though I stir constantly while heating, typically.
I aerate well with a mixstir, pitch plenty of yeast, either from a starter (the bitter was a 1qt starter of WY1468) or rehydrated US-05. Oh, and these are 3 gallon batches, by the way.
Could what he suggested have some validation? I’d never thought of it before, but it makes some sense to me.
Direct heating mashtun and denaturing some of the enzymes causing poor attenuation. I don’t think I’ve had a brew in a bag batch finish under 1.016 to date. And yes, I’ve calibrated my hydrometer.
There could indeed be something to this, especially for smaller batches like the 3 gallons you are talking about.
You say you have calibrated your hydrometer… but have you calibrated your thermometer also? Perhaps you are really mashing at like 161 F and then your beta amylase enzymes are gone.
To rub in a bit of salt, I brew 2 or 3 gallon batches all the time, and I have no problems hitting 1.013 or less. But I also don’t direct fire on my mash tun. If anything, I’ll boil some water on the side and add that in, rather than heating the tun itself. I also typically mash at 148-150 F. You might want to consider doing the same.
Okay, good ideas. I have a thermopen, so I’m doubting that is too far off, if any. Perhaps I should try not direct firing the mashtun at all, until I want to mashout.
Just afraid of losing too much heat while mashing.
Just had never consider that maybe some enzymes are getting denatured…I can’t figure out what else would be causing under attenuation. With US-05 nonetheless!
[quote=“Beersk”]Just had never consider that maybe some enzymes are getting denatured…I can’t figure out what else would be causing under attenuation. With US-05 nonetheless![/quote]If you’re denaturing the enzymes, your efficiency would be impacted but I don’t see why it would affect fermentability of the wort that was produced prior to the denaturing. I think you’re chasing the wrong rabbit.
If you’re denaturing all your Beta amylase, leaving only Alpha amylase, you would get a less fermentable wort, but would that account for such a high final gravity?
If you’re denaturing all the amylase, you’ll have lots of starch left in your wort, but starch is less dense than sugar, so you shouldn’t get your expected gravity. To be excessively careful you could do an iodine test to see if you had complete conversion, but at 1.041 it sounds like you got there.
Your yeast pitching and aeration sound right.
It really sounds like something is disrupting your fermentation.
It’s just confusing. I’m hitting my OGs if not over shooting them, pitching lots of yeast, aerating, giving them 2-3 weeks on the yeast, they should be reaching the final gravities I’m wanting. I adjust for pH using Bru’n water, also. With the exception of the lactic acid addition it always recommends for the sparge/kettle, I skip that part. But that should be cause for attenuation stopping short. If what Shadetree says is true, then it’s still a mystery. But if it’s denaturing enzymes, but leaving unconverted starches that are still read by the hydrometer, then that may be my answer. I don’t know. I brewed tonight with my cooler setup and pitched harvested yeast. We’ll see where that one lands.
Still, I’d like to get an answer to this mystery…
If y’all have any more thoughts, please share them.
[quote=“Beersk”]Still, I’d like to get an answer to this mystery…[/quote]When do you start heating? I assumed that you would hit your target temp, insulate, mash for ~30 minutes, then check the temp and add heat if needed, so only one, maybe two, re-heats per mash. If this is how you’re doing it, seems to me that the main part of the mash is already over and that even if you were letting a large portion of the wort heat into the 170s or higher before stirring and denaturing say 50% of your enzymes, that the fermentability ought to be pretty stable at that point anyway. But, if you’re doing a lot of little re-heats throughout the mash, maybe you could negatively impact the beta enough to make a less fermentable wort.
Every 15 minutes, I check and add heat, typically. Sometimes I’ll keep the electric burner on the lowest setting, so this may be the issue. Next time I do a brew in a bag, I’m not going to add any heat at all, but instead will insulate the kettle and let the temp drop. Want to see if that makes the difference.
Perhaps I wasn’t mashing long enough either. I’ve been doing 75 minute mashes, most things I read say you should do 90 minute mashes. I don’t know that that extra 15 minutes would make that big of a difference though.
Keeping the burner on all the time might be the problem. If you heat once or twice and stir often (or constantly preferably) and use insulation to maintain the temp, you won’t impact the enzymes.
Well, this may be the issue then. Time to run the experiments.
Thanks for the help and I’ll try to remember to post some sort of update regarding my next brew in a bag batch.
FYI – I only mash for 40 minutes, and average efficiency is 85-90%, and attenuation is perfectly normal. No need to mash for 75-90 minutes. Waste of time. Brew day doesn’t have to be 4.5 to 6 hours. You can get it done in 3.5 to 4 hours if you really want – I want! Now I make 2-gallon batches in about 3.5 hours. Even doing a double decoction, “for fun”.
I cooler mash not biab, but a couple times I have over heated strike water. And ended up mashing in around 165. I got the temps down with cold water and stirring but it took 10 to 15 min. I don’t have good enough notes to be positive but I swear those batches attenuated poorly.
Good call, I’ve been questioning the reasons for that. And also doing a mashout. Doesn’t seem necessary. Doubt it’s boosting the efficiency that much. My brews in a bag batches have been 3 gallons or so.
bdaugherty, there must be something to that. Mashing too warm, direct heating mash without enough circulation, has to denature some of those enzymes. But I can’t know for sure until I run some experiments. But to be honest, I’m not in too much of a hurry to do those experiments when my cooler setup suits me fine. But it is fun to do something different once in a while.
[quote=“Beersk”]So I’ve done several brews in a bag and always seem to have an issue with beers stopping around 1.018-1.020, even a bitter I brewed recently and mashed at 151 with a starting gravity of 1.041. I mentioned it to another brewing friend the other day and he said, well, it could be that when you’re direct firing the kettle, down at the bottom of the mashtun, some of the enzymes could be denatured because it’s likely very much hotter on the bottom than it is in the rest of the mash. Even though I stir constantly while heating, typically.
I aerate well with a mixstir, pitch plenty of yeast, either from a starter (the bitter was a 1qt starter of WY1468) or rehydrated US-05. Oh, and these are 3 gallon batches, by the way.
[quote]Could what he suggested have some validation? I’d never thought of it before, but it makes some sense to me.[/quote]Direct heating mashtun and denaturing some of the enzymes causing poor attenuation. I don’t think I’ve had a brew in a bag batch finish under 1.016 to date. And yes, I’ve calibrated my hydrometer.
Thoughts?[/quote]
He is correct. I was doing a partial mash a few days ago. This time I used a single grain bag. Before I always used 4 small grain bags. With the single bag I could not hold the temperature at 152°. Temp was always dropping into the mid 40°s even with stirring constantly and applying low heat. I lifted the grain bag and stuck the thermometer underneath it. 176°. I’m hoping I didn’t do to much damage.
FWIW, I BIAB in a cooler instead of my kettle and have no issues with attenuation. There may be something to the idea that you’re getting enough of a hot spot from your burner to denature some enzymes, especially since you’re brewing smaller batches.
I don’t know what else it could be, seriously. I’m pitching plenty of yeast, aerating plenty with a mix stir, giving it 2-3 weeks in the primary…I mean, what else can I do? Pretty frustrating though, because it turns out kind of crappy beer.
I don’t know what else it could be, seriously. I’m pitching plenty of yeast, aerating plenty with a mix stir, giving it 2-3 weeks in the primary…I mean, what else can I do? Pretty frustrating though, because it turns out kind of crappy beer.[/quote]
If it’s feasible, you could try a double-boiler arrangement if you have a larger kettle to fit your BIAB kettle in. Or maybe put the kettle in your oven during the mash if it fits. Or you could reserve a pound or so of base malt and do a separate mini-mash at a low temp, then add that in for the last 15-20 minutes of the mash to add some extra enzymes late in the process.
Or you could test out Kai’s experiment of adding enzymatically active wort to the fermenter:
