High FG

[LJvermonster]

Hi Folks,
Switched to eBIAB this year and my FG is terrible.

Brewed twice. First OG was 1. 050 second was 1.063 and FG were 1.020 and 1.022.

Yeast was a new Conan pack.

I have had some challenges with mash temp - it could have been high in the low 160s.

My pH has been in the 4.8 range. Not sure what to do with that.

Any suggestions?

 

[RM-MN]

Things that come to my mind:
1. BIAB allows a fine grind or crush.
2. If you have a fine grind or crush, conversion will complete very quickly.
3. Low 160's leads to more alpha amylase activity which should lead to more dextrinous wort.
4. More dextrines in the wort should give you a higher FG which you indicate. I would have expected FG around 1.012 to 1.018 with a lower sacharinization temp.
5. Your pH probably has little to do with the FG. It would be nice to have it a bit higher and some additions to your water might get it there. However, measuring pH is not easy as the pH of the mash will be changing for at least 15 minutes into the mash.
6. Now that you "know" that your mash was probably too high of a temp, you can adjust your strike temp to bring that in line for the next batch.
7. Depending on the batch size and OG, one pack of Conan yeast might have been an underpitch. Using more yeast often will lead to a lower FG.

 

[DBhomebrew]

How are you measuring your final gravities? Refractometer?

Have you checked your mash thermometer calibration?

What volume batch size?

Aerate or oxygenate just before pitch?

Use a starter?

How old were the yeast packs? How stored?

 

[LJvermonster]

How are you measuring your final gravities? Refractometer? Hydrometer

Have you checked your mash thermometer calibration? Yes - It's been off, this is what I think I'm running high. Water was boiling and it was reading 202 degrees.

What volume batch size? 5.5gal

Aerate or oxygenate just before pitch? Pump from keggle and I raised the hose above and the wort splashes vigorously in the bucket.

Use a starter? Not on the past two. Was thinking I would at least make a starter for the next run.

How old were the yeast packs? How stored? - First batch 1 month, 2nd batch used harvested yeast from batch one. Both stored in fridge.

 

[DBhomebrew]

When you reported your mash as low 160s, had you already adjusted for the thermo's miscalibration or was your mash really in the high 160s / low 170s?

 

[LJvermonster]

When you reported your mash as low 160s, had you already adjusted for the thermo's miscalibration or was your mash really in the high 160s / low 170s?

It was reading low-mid 150s and I added the 10 degrees to figure I was in low-mid 160s.

 

[doug293cz]

High initial mash temps will denature the Limit Dextrinase fairly quickly. This is the important enzyme that hardly anyone talks about. Limit dextirnase breaks the branching bonds (the 1-6 bonds) in amylopectin. This reduces the amount of dextrins you will have in the final wort, IF the amylase enzymes are allowed to work to completion (nothing left but fermentable sugars, and dextrins that are too small for alpha or beta amylase to hydrolyze.) The more time limit dextrinase has to work the less limit dextrins you have in the final wort, and the lower the FG will be.

Brew on

 

[CascadesBrewer]

It was reading low-mid 150s and I added the 10 degrees to figure I was in low-mid 160s.

I feel like this is the simple answer here. There is a very clear connection between mash temp and fermentability. A 160F mash will result in low fermentability and a high FG.

I am curious how the beers have tasted. There is this "common knowledge" that a high mash temp will result in a thick and sweet beer, but my experience mash temps have very little impact on these characteristics.

 

[RM-MN]

I feel like this is the simple answer here. There is a very clear connection between mash temp and fermentability. A 160F mash will result in low fermentability and a high FG.

It isn't as simple and the connection between mash temp and fermentability is rather tenuous when you BIAB and mill the grain very fine. I get approximately the same FG from a 152 mash as a 158 mash because with the very fine grind the conversion happens so quickly that none of the enzymes have a chance to denature. You need a much coarser milling so your enzymes can denature.

 

[RM-MN]

Switched to eBIAB this year and my FG is terrible.

Brewed twice. First OG was 1. 050 second was 1.063 and FG were 1.020 and 1.022.

Yeast was a new Conan pack

How does the beer taste? Can you tell the difference reliably between an FG of 1.015 and 1.020? Most people probably cannot. If your beer tastes good, quit worrying about the exact number and just enjoy the brewing and the drinking.

 

[LJvermonster]

How does the beer taste? Can you tell the difference reliably between an FG of 1.015 and 1.020? Most people probably cannot. If your beer tastes good, quit worrying about the exact number and just enjoy the brewing and the drinking.

The first one was much sweeter then it should have been (plain ale). 2nd I just kegged but it tasted better..

I'm going to get a new thermometer and check that against my brew commander, verify my mash temp and make a starter, maybe my yeast wasn't great?

 

[CascadesBrewer]

It isn't as simple and the connection between mash temp and fermentability is rather tenuous when you BIAB and mill the grain very fine. I get approximately the same FG from a 152 mash as a 158 mash because with the very fine grind the conversion happens so quickly that none of the enzymes have a chance to denature. You need a much coarser milling so your enzymes can denature.

Maybe it varies between systems and process but this has not been my experience. I mill fine and do BIAB and still see a correlation between mash temp and attenuation, especially if I mash up near 160F. I believe it was data from Kai Troester showing that denaturing happened mush faster with a fine grain crush and that in the 160F range, Beta Amylase was denatured in around 5 minutes. (Edit: I could not find a reference from Kai about grain crush and denaturing, but there is data that denaturing occurs faster with a thin mash which is typical of BIAB.)

 

[doug293cz]

Maybe it varies between systems and process but this has not been my experience. I mill fine and do BIAB and still see a correlation between mash temp and attenuation, especially if I mash up near 160F. I believe it was data from Kai Troester showing that denaturing happened mush faster with a fine grain crush and that in the 160F range, Beta Amylase was denatured in around 5 minutes.

I don't recall seeing anything on grind coarseness effects WRT rate of denaturing in Kai's writings. Do you have a link?

Brew on

 

[Kickass]

What’s your altitude? I boil at 204* (4500ft elevation) your thermometer might not be as inaccurate as you think.

 

[CascadesBrewer]

I don't recall seeing anything on grind coarseness effects WRT rate of denaturing in Kai's writings. Do you have a link?

It could be that I am thinking that enzymes denature faster with the thin mash of BIAB??

I recall doing some research into a batch where I mashed in too high, stirred for 10 minutes to lower the temp, but the beer ended up with a high FG. I recall this thread: How fast do enzymes denature?

That thread has a graph and a link from Starch Conversion - German brewing and more

With a skim of a few of his articles, nothing jumps out on me about the "grain crush to denature time" connection.

 

[doug293cz]

It could be that I am thinking that enzymes denature faster with the thin mash of BIAB??

I recall doing some research into a batch where I mashed in too high, stirred for 10 minutes to lower the temp, but the beer ended up with a high FG. I recall this thread: How fast do enzymes denature?

That thread has a graph and a link from Starch Conversion - German brewing and more

With a skim of a few of his articles, nothing jumps out on me about the "grain crush to denature time" connection.

Yes, the literature says enzymes denature faster in thinner mashes, but Kai found that thinner mashes convert faster. There are variables in addition to enzyme lifetime that affect the rate of conversion.

Brew on