Wort Fermentability w/ BIAB

[Desertbrewer]

Since I began brewing about 2 years ago, I've done various iterations of BIAB (used different fineness of bags, tried no sparge vs. "dunk" batch sparge, etc). One common theme, besides progressively making better beer, has been extremely fermentable wort; I have never had a beer finish above 1.010, even 8% porters and stouts with over a pound of crystal malts and other specialties.

I'm certain it is not my hydrometer; I've gone through 2 and both were calibrated correctly. I'm also basically certain I am not over pitching yeast. It doesn't matter whether I pitch a ton of yeast or just a packet, my beers ferment out. I've experimented with mash temp; it seems to make no difference on my system whether I mash at 150 or 164 F. Also, I have been using RO water from the store, and hitting my mash pH with salts and acid. I used to have the LHBS mill my grains for me, and I would forgo double milling them because I got good enough efficiency. Now, I have my own grain mill and crush relatively fine, like most of you other BIAB'ers. I have a temp controlled mini fridge, and it doesn't seem to matter how cool I ferment. Are there any other variables I'm missing?

You can certainly see why this is frustrating to me; it makes brewing malty beers less appealing to me, because they come out lacking the body and even malt flavor.

One thing I haven't mentioned, which I think may be the key in having thought about this for a long time now. Mash time. I've always heard you want to mash until those enzymes have all converted so that you had a fermentable wort, but perhaps for the BIAB process, grind of the grain, and whatever other variables seem to exist, at least for me, it helps the beer to actually cut the mash rest short, leaving behind some desirable unfermentables so that the beer has "beeriness" (something that my thin, overattenuated beers lack).

I was thinking on my next batch, a simple SMaSH, to test the extreme and just mash for 15 minutes, for a benchmark on what that variable does to the fermentability.

Am I on the right track thinking to cut my mash time? Is there anyone else who has experienced this?

 

[bleme]

If I want a maltier beer, I use a yeast like S-04 that doesn't attenuate as much. You can definitely try shorter mash times but you will need to do an iodine test. Long chain sugars are fine, but you don't want starches in your wort.

 

[rhys333]

First thing that comes to mind is that you're mashing a lot cooler than intended. Have you checked your thermometer against another one to make sure it's hitting desired temp? Also, some BIAB brewers experience heat loss when mashing, which can create a more fermentable wort. As long as it's not some sort of infection you're dealing with, I'm thinking low mash temp is the primary suspect.

 

[isomerization]

First thing that comes to mind is that you're mashing a lot cooler than intended. Have you checked your thermometer against another one to make sure it's hitting desired temp? Also, some BIAB brewers experience heat loss when mashing, which can create a more fermentable wort. As long as it's not some sort of infection you're dealing with, I'm thinking low mash temp is the primary suspect.

I think this is definitely on the right track, as there shouldn't be anyway that a true 164F mash attenuates to that degree, right?

 

[trav77]

First thing that comes to mind is that you're mashing a lot cooler than intended. Have you checked your thermometer against another one to make sure it's hitting desired temp? Also, some BIAB brewers experience heat loss when mashing, which can create a more fermentable wort. As long as it's not some sort of infection you're dealing with, I'm thinking low mash temp is the primary suspect.

This. How are you insulating while mashing? Are you taking temp readings throughout the course of the mash or just at mash in?

 

[doug293cz]

You may also want to look at not crushing as fine. The finer the crush the faster the gelatiniztion process. And, once the starch is gelatinized, conversion happens very quickly.

There's a third important saccharification enzyme called Limit Dextrinase that doesn't get as much attention as alpha and beta amylase. Unlike the amylases, limit dextrinase breaks the branching links in amylopectin. This allows it to break down non-fermentable dextrins into chunks that can be cut into fermentable sugars by the amylases.

Limit dextrinase is even more thermally unstable than beta amylase, so it doesn't last long enough in most mashes to have a big effect. If it's all denatured before much gelatinization occurs, then it can't cut up many dextrins. However, with a very fine crush, and rapid gelatinization, limit dextrinase can become significant, thus leading to more fermentable wort. Crushing a little coarser can extend your gelatinization time, and thus reduce the effects of limit dextrinase.

Shorter mash times can also be helpful to limit the total amylase action and leave more unfermentable sugars. In this case you want to heat to a boil as quickly as possible after pulling the bag, in order to denature the amylase.

Finally, you're not the first to report this "problem" @RM-NM is also a very fine grind BIAB'er who has seen similar effects. I think he does mostly 20 - 30 min mashes. He doesn't like to go shorter as he finds that beers with 10 - 15 min mashes lack flavor.

Brew on

 

[Morrey]

What yeast strains are you using?

 

[Desertbrewer]

First thing that comes to mind is that you're mashing a lot cooler than intended. Have you checked your thermometer against another one to make sure it's hitting desired temp? Also, some BIAB brewers experience heat loss when mashing, which can create a more fermentable wort. As long as it's not some sort of infection you're dealing with, I'm thinking low mash temp is the primary suspect.

Admittedly, I dont have a nice one like a Thermapen, its just a normal glass one that came with my initial brew kit. I tested it once by boiling water and making an ice bath and it was within about 1-2 degrees on the high and low end.

I live in a warm climate so I haven't really found it necessary to insulate but I can try next time with a sleeping bag. Also I have neoprene from some old wetsuits I could try to jury rig.

Either way, I have been mashing at like 164 every time I brew because of this phenomenon. And at the end of an hour mash, usually the temp has only dropped 4 degrees.

What would happen if I tried just mashing at something like 170, according to my thermometer?

You may also want to look at not crushing as fine. The finer the crush the faster the gelatiniztion process. And, once the starch is gelatinized, conversion happens very quickly.

There's a third important saccharification enzyme called Limit Dextrinase that doesn't get as much attention as alpha and beta amylase. Unlike the amylases, limit dextrinase breaks the branching links in amylopectin. This allows it to break down non-fermentable dextrins into chunks that can be cut into fermentable sugars by the amylases.

Limit dextrinase is even more thermally unstable than beta amylase, so it doesn't last long enough in most mashes to have a big effect. If it's all denatured before much gelatinization occurs, then it can't cut up many dextrins. However, with a very fine crush, and rapid gelatinization, limit dextrinase can become significant, thus leading to more fermentable wort. Crushing a little coarser can extend your gelatinization time, and thus reduce the effects of limit dextrinase.

Shorter mash times can also be helpful to limit the total amylase action and leave more unfermentable sugars. In this case you want to heat to a boil as quickly as possible after pulling the bag, in order to denature the amylase.

Finally, you're not the first to report this "problem" @RM-NM is also a very fine grind BIAB'er who has seen similar effects. I think he does mostly 20 - 30 min mashes. He doesn't like to go shorter as he finds that beers with 10 - 15 min mashes lack flavor.

Brew on

Great info, thanks Doug. That does make me want to experiement to find the "sweet spot" between gelatinization and those other enzymatic processes. It does take a while for my wort to come up to a boil, sounds like that may be a factor as well. Lots to think about.

What yeast strains are you using?

I've used a lot, right now I'm using the Conan strain from Gigayeast. My first pitch of it was into a 1.060 IPA and it fermented down to 1.007. I have the opposite problem from everyone else on here.

 

[Morrey]

Yeah, you sure are. Many have mentioned having to go to the second generation of Conan yeast to get that finishing number. Maybe what others are saying earlier.....a bit larger grist to slow conversion down and shorter mash times.

 

[davemattb]

I had a similar issue on my first few biab. Almost enough to stop doing it. Various yeasts. However biab is so much more convenient so I wanted to make it work. The last few batches I have conditioned my grain. It doesn't seem to flour as much. I also switched to a batch sparge. Last 3 beers have been some of my best yet. I just upgraded to thermapens so hopefully can better dial in my mash temp. I've also switched from ro to bottled spring water/tap water combo. Not sure what made the difference but definitely maltier. Haven't checked fg as I'm more concerned with flavor. Good luck, and I'll be interested in what makes the difference for you!

 

[rhys333]

You could just go with coarser grind. I do that with a quick dunk sparge and get 80-82% efficiency plus tight control over fermentability.

 

[makisupapolice14]

Buy a good thermometer and insulate well with reflectix and sleeping bag and get back to us

 

[Desertbrewer]

Buy a good thermometer and insulate well with reflectix and sleeping bag and get back to us

I didn't realize how general the consensus was that insulating the vessel was such an important factor. I've brewed multiple times when the weather is 100+ degrees out and didn't read a drastic temp drop. Definitely worth a try though to figure out if that's what's hurting me.

 

[Sadu]

I had this same problem. My issue was cheap thermometers leading to mashing too cool. Start by getting an instant read digital thermometer. Mash a few degrees higher. Definitely insulate, and when you check the mash I like to add a litre of boiling water if the temps have dropped too far. Try adding a bit of oats or wheat instead of crystal - you get body without the sweetness. And adding some calcium chloride does wonders for making a beer seem more full bodied.

 

[bajaedition]

I had this same problem. My issue was cheap thermometers leading to mashing too cool. Start by getting an instant read digital thermometer.

I admire you for getting an instant read, those are nice

I want to say that some of the cheaper instant reads can have issues also

what the problem in probe thermometers is that the cheaper ones use bi metal sensors in the probe. and those can get out of calibration from brew to brew. I have what is called a calibration thermometer so I can set them every brew

what you want to find is a thermometer that has a resister in the probe, they are much more accurate. But even these need to be calibrated once in a while, and make sure the probe is waterproof. You will not be happy if you get one that floods out mid mash because of cheap welds on the probe.

Saying that, I use a 24 dollar BBQ unit that has a remote you can wear on your belt. it has alarm features and keeps you constantly updated with the temp. It also has, like any good unit, a calibration feature. In 2 years of use I have had to calibrate it twice, and that was by 1 degree.

Temperature and PH, you need good tools for each. I actually think a floating thermometer is more accurate than most probe thermometers sold at brew stores. Even my 40 dollar probe I have to calibrate every once in a while. It was not until I went over to electronic ones (resister) that I got thermometers that were accurate from brew to brew.

 

[Desertbrewer]

I brewed a cream Ale today.

7.5lb 2 row
1.5 lb cornmeal, cereal mashed

Mashed at 155 for 25 minutes, insulated the cooler with an old wetsuit and tied it up with rope. OG was 1.052.
Pitched 1 pack of Notty

Not trying to disregard any of your guys great advice, I just feel the thermometer is not my 'primary' issue. About grind fineness; I used to mill my grain at a MoreBeer retail store on mills set for lautering and had the same problem I'm describing today. Could be temp loss, my hunch is mash time.

Will report back with what happens. Thanks all for the helpful comments and things to consider to improve my brewing [emoji482]

 

[Bobby_M]

I think your thermometer is the primary issue. You would probably have to chew the beer and visit a dentist if you really mashed at 164.

 

[trav77]

I think your thermometer is the primary issue. You would probably have to chew the beer and visit a dentist if you really mashed at 164.

My guess is it's a mix of: no insulation, inaccurate thermo, potentially long mash time (?) although without the first 2 issues, a 60 min mash should not give you the issues you've been having.

I agree with Bobby if you were really mashing at 164 F you would actually be above the temp range for alpha amylase and WAY above for beta. It would give you very poor conversion and what you did get out of it would be a lot of longer chain sugars and dextrins which would be relatively less fermentable... the opposite problem of what you're experiencing.

I think your thermo is off, you're starting your mash much lower than expected, and the lack of insulation is causing it to drop. That combined with a fine crush and longer mash time probably means you're spending a lot of time at the end of the mash time in <150 F territory maybe even well below that, creating a very fermentable wort.