BIAB-Does mashing with full volume... mash too thin? Off flavors?

[Jayjay1976]

I've brewed about three dozen batches now, elec biab with full volume of water and a superfine crush. I've recently learned that a really thin mash can hamper efficiency and cause off flavors. I typically start with 8.3-8.5 gallons of RO with salts in order to end up with 6.5G in the fermenter. My typical grain bill is about 15 lbs of grist at 70% efficiency and I almost always hit my pre- and post boil numbers with a mash thickness of about 2.25 qt/lb. Does that seem excessively thin? What effect would this have on the flavor of my beers?

 

[cubalz]

2.25 qt/lb is what I have always used will no ill effect to my beer flavor. Brew on!

 

[balrog]

What off flavors are purportedly generated by thin (put a number on that) mashes?

I, too, have always BIAB full volume no sparge and I'm wondering what flavor I should be finding.

 

[Jayjay1976]

What off flavors are purportedly generated by thin (put a number on that) mashes?

I, too, have always BIAB full volume no sparge and I'm wondering what flavor I should be finding.

I dunno, kind of a grainy, husky, kinda bitter aroma and off flavor. If 2.25qt/lb isn't too thin then I might be crushing too fine. That would be the only other variable I've never tweaked. I run a cereal killer at almost the smallest gap, I'll try opening it up a bit. Thanks for the comments.

 

[Jayjay1976]

I always thought this was a recipe or water chemistry issue, but then I attended an advanced brewing class recently. The crush they used was way coarser than what I get and the instructor also mentioned that thin mash might be a problem. Not all of my beers have it, but it seems to happen more often with moderate gravity 1.060-ish beers, both dark and light.

 

[balrog]

Hm. Interesting. I use a corona mill and it is likely much finer than any roller mill makes but it also is likely more variable within the crush than a roller mill. I am not sure I have gotten husky, but I am uncertain of my olfactory prowess.

 

[cubalz]

Honestly, if you are doing full volume, no sparge with 2.25qt/lb AND even if you grind your grain into total flour neither of those things can cause off flavors. Can you describe the off flavors you are experiencing? I am wondering if it has anything to do with your chosen grain bills....

 

[jjw5015]

I've brewed about three dozen batches now, elec biab with full volume of water and a superfine crush. I've recently learned that a really thin mash can hamper efficiency and cause off flavors. I typically start with 8.3-8.5 gallons of RO with salts in order to end up with 6.5G in the fermenter. My typical grain bill is about 15 lbs of grist at 70% efficiency and I almost always hit my pre- and post boil numbers with a mash thickness of about 2.25 qt/lb. Does that seem excessively thin? What effect would this have on the flavor of my beers?

Have you gotten off flavors in the 3 dozen batches you've done? If not, I think you've already answered your own question.

 

[Redpappy]

I dunno, kind of a grainy, husky, kinda bitter aroma and off flavor. If 2.25qt/lb isn't too thin then I might be crushing too fine. That would be the only other variable I've never tweaked. I run a cereal killer at almost the smallest gap, I'll try opening it up a bit. Thanks for the comments.

My first few brews as a full BIAB, I was having the same off flavors, very grainy. Through some more questions and some more research, I changed my water to a 50/50 mix of filtered tap and RO water. With that change, and using BrewNWater, I have gotten rid of majority of the off flavors. I tend to use the full amber on the water profile..

I also use a cereal killer, setting to as low as it can go. My stats are pretty much like yours 70% Efficiency.if you change your settings can you share your results?

 

[McKnuckle]

...the instructor also mentioned that thin mash might be a problem.

People always have to offer something, even if they really have no clue. Don't pay too much attention to this one. If it were a real issue, you'd have a million discussions about it, and several solutions on the table.

A bitter off-flavor is sometimes associated with excessive alkalinity and a high mash pH, especially in pale beers. Might want to re-visit your water treatment, but don't worry about the mash thickness.

 

[soccerdad]

If BIAB were a cause of my off flavors, I would always have off flavors because I always BIAB. But I don't. The times that I do have off flavors I can typically trace back to 2 things .. 1) ferm temp went somewhere unexpected, or 2) I was trying out a new yeast and was not enamoured with the flavor profile.

 

[Yooper]

What kind of mash pH are you getting with the thin mash? I find that if my pH is higher than 5.5 or so in the mash of lighter color beers, I get a bit of graininess/husk that isn’t wanted. Could that be possible in your case?

 

[Jayjay1976]

What kind of mash pH are you getting with the thin mash? I find that if my pH is higher than 5.5 or so in the mash of lighter color beers, I get a bit of graininess/husk that isn’t wanted. Could that be possible in your case?

TBH I have never actually measured my mash pH. I've relied on the predictions in brewersfriend and always adjust down with a few oz of acid malt to get it in the 5.2-5.3 range.

I do have a pH meter, just haven't learned how to use it yet. This sounds like a likely culprit, especially since you describe a similar flavor, and also because my stouts don't usually have this flavor. Perhaps thats due to the more acidic dark roast malts. I don't typically add any acid malt to dark beers, either.

 

[Bobby_M]

The thinner the mash is, the more the pH can be affected by the water profile. That's all you can say about it. Whether it is a negative effect has more to do with being unaware or unprepared with water mods including acidification when necessary. In other words, for someone that uses their tap water because it tastes fine and then moves from a batch sparge process to full volume mashing, it MAY be an issue. A brewing instructor likely never even contemplated a full volume mash because it's not something a pro brewer would do. A lot of ass talking there.

 

[RM-MN]

TBH I have never actually measured my mash pH. I've relied on the predictions in brewersfriend and always adjust down with a few oz of acid malt to get it in the 5.2-5.3 range.

I do have a pH meter, just haven't learned how to use it yet. This sounds like a likely culprit, especially since you describe a similar flavor, and also because my stouts don't usually have this flavor. Perhaps thats due to the more acidic dark roast malts. I don't typically add any acid malt to dark beers, either.

When you do use the pH meter you will discover that the mash pH is a moving target. By the time the pH has somewhat stabilized so much of the conversion is over that adding acid at that time is too late to affect the outcome. Take notes of each batch you make and note the pH, then make adjustments for the next similar batch to approach the mash pH you think you want.

 

[Miraculix]

I use a really fine crush and brewed very low gravity beers with full volume biab. 1.025 and below og beer.

Never had issues with off flavour, but I keep my alkalinity as low as possible and add a bit of acidulated malt, about 2% of the grain bill in addition as acidulated malt.

 

[Yooper]

TBH I have never actually measured my mash pH. I've relied on the predictions in brewersfriend and always adjust down with a few oz of acid malt to get it in the 5.2-5.3 range.

I do have a pH meter, just haven't learned how to use it yet. This sounds like a likely culprit, especially since you describe a similar flavor, and also because my stouts don't usually have this flavor. Perhaps thats due to the more acidic dark roast malts. I don't typically add any acid malt to dark beers, either.

As the others said, it could be the full volume mash and the water. Even though you’ve got great predictions, it could be that you have more alkalinity in your water than in your profile you’re using, or it could be that the malt has less acidity than in the software, etc.

If I can use a pH meter competently, I know you could too- and that would be the first thing to check. Try a 2 pound test mash and see what sort of pH you get for practice, before making a full mash to see if your additions actually match the pH predictions.

 

[Jayjay1976]

Thanks for all the great comments, I'm going to dig in to the pH and maybe I'll finally tackle water chemistry.

 

[Miraculix]

Thanks for all the great comments, I'm going to dig in to the pH and maybe I'll finally tackle water chemistry.

A really rough guideline would be to throw in some acidulated malt by guessing, usually it's 2% of the total grain bill on top of the existing grain bill. I know it's not a scientific approach, but does the job for me and many others.