FG of 1.023 what happened???

[aaronius79]

Hi fellow brewers, I am trying to figure out something regarding my current gravity reading. I am 9 days into fermentation. Here is what I did...


Grain bill

6 gallon batch...

8 lbs smoked malt
4 lbs munich
1 lb cararoma
.5 lb chocolate malt
1lb corn sugar

BIAB method. Mashed at 160 for 60 minutes and then did a "sparge" pouring 2 gallons of 170 degree water evenly and slowly over the grains after straining them.

1 oz hallertau hops at 60 minutes
1 oz hallertau hops at 30 minutes

whirlfloc tablet at 10 minutes



Projected OG was 16 brix.. my true OG was 16 brix


I'm 9 days into fermentation.. It started about 12 hours after pitching (pitched at 68 degrees) and strong fermentation for about 3 days and then slowed down at about day 4-5 and shows pretty much llittle to no activity at this point. I just did a gravity reading and its at 10 brix. corrected for alcohol comes to 1.023 gravity


1)SHould I expect this number to come down to like 1.020 or is this thing done at 1.023?


2) the beer recipe calculator predicted a final gravity closer to 1.014. How come I'm so far off? I know a higher mash produces less fermentable sugars but I didn't calculate it being that much of an impact.

3) Do I have a stalled fermentation? temps have been between 64-67 degrees the whole time.


All in all the beer at this point tastes pretty darn good but I was expecting an ABV closer to 7% but looks like its more like ~5.7%

 

[jake-k]

Did you purposely mash at 160? That's pretty high and leaves unfermentable sugars that yeast wont consume. I'm guessing that is the problem. Mashing high can also extract tannins as well.

Edit: I see you already new this. Cheers.

 

[jake-k]

I would leave it for a week and check again, but I'm thinking its about done.

 

[Big Monk]

Mashing at 160 is probably your culprit.

Can you explain 2.)? What do you mean by, "...but I didn't calculate it being that much of an impact."?

 

[jrowland74]

Are you using a refractometer? Try with a hydrometer. The calculators for post fermentation with a refractometer are notoriously inaccurate

 

[doug293cz]

Are you using a refractometer? Try with a hydrometer. The calculators for post fermentation with a refractometer are notoriously inaccurate

You do need to use an alcohol compensation calculator when measuring fermented wort with a refractometer. With a good calculator like this one, refractometer measurements of FG are not "notoriously inaccurate." It's true than hydrometers are more accurate, but the refracts are usable (you won't be off by more than a couple of points.)

Brew on

 

[AZCoolerBrewer]

I'm guessing since he said the beer tastes good that he drank his hydrometer sample after measuring it.

I am fairly new to the trade, but all the books say that mash should be between 150 and 160. Most folks on here dry out their beer by pushing the low end, even as low as 148. I suspect that 160 will work, but not covert all the starches to sugars. Of course the beers don't read books, so I could be wrong. Why not give it a week and see if it attenuates a little further?

 

[treacheroustexan]

I would also agree that the 160 is the culprit. But since you're only 9 days, it wouldn't hurt to give it another week and check again.

 

[aaronius79]

Thanks for the feedback. Il give it another week and next time do a hydrometer reading instead of refractometer. I mashed at 160 cause I wanted a malty body.

 

[wildestripe]

Just an idea (more to confirm to myself more than anything ...) but looking at the Diastatic power of Smoked Malt, Cararoma, and Chocolate they are all 0 yet they form 70% of your grain bill. Munich is only rated at 72.

Is it possible without more base malts, there wasn't enough enzymes left over from the Munich to fully convert the specialty grains?

 

[doug293cz]

Just an idea (more to confirm to myself more than anything ...) but looking at the Diastatic power of Smoked Malt, Cararoma, and Chocolate they are all 0 yet they form 70% of your grain bill. Munich is only rated at 72.

Is it possible without more base malts, there wasn't enough enzymes left over from the Munich to fully convert the specialty grains?

If that's the case, OP could have a whole lot of unfermentable dextrins. One possible "fix" is to add some alpha amylase enzyme to the fermenter. The enzyme should be available at a good LHBS, and is easily ordered on-line.

Brew on

 

[cantrell00]

Just an idea (more to confirm to myself more than anything ...) but looking at the Diastatic power of Smoked Malt, Cararoma, and Chocolate they are all 0 yet they form 70% of your grain bill. Munich is only rated at 72.

Is it possible without more base malts, there wasn't enough enzymes left over from the Munich to fully convert the specialty grains?

You would have seen that in the pre boil OG if that were the case.

 

[doug293cz]

You would have seen that in the pre boil OG if that were the case.

Not necessarily. A lot of the original starch will go into solution, thus raising the SG. At that mash temp, the beta amylase would be quickly denatured, so there would be little maltose production. There might not have been enough alpha amylase to reduce the starch to mono and di-saccharides plus limit dextrins, but there would be some fermentable sugar created along with lots of complex dextrins, and probably some residual starch. All of that would be in solution contributing to the OG.

Brew on

 

[cantrell00]

Not necessarily. A lot of the original starch will go into solution, thus raising the SG. At that mash temp, the beta amylase would be quickly denatured, so there would be little maltose production. There might not have been enough alpha amylase to reduce the starch to mono and di-saccharides plus limit dextrins, but there would be some fermentable sugar created along with lots of complex dextrins, and probably some residual starch. All of that would be in solution contributing to the OG.



Brew on

So confused. So it would convert into non fermentables?

I think I am following you. But wouldn't that show as a 1 to 1 relationship in the SG. Ex, if OG was 1.050, & 20 points of that gravity were too complex to ferment, the SG would reflect those 20 pts as well.

Similar to adding lactose. Boost in OG & SG by the same number of gravity points.

1.023 implies that there was a good relationship of fermentable & non fermentable sugars, right?

It's not that far off given that the sacc rest of 160.

 

[doug293cz]

So confused. So it would convert into non fermentables?

I think I am following you. But wouldn't that show as a 1 to 1 relationship in the SG. Ex, if OG was 1.050, & 20 points of that gravity were too complex to ferment, the SG would reflect those 20 pts as well.

Similar to adding lactose. Boost in OG & SG by the same number of gravity points.

1.023 implies that there was a good relationship of fermentable & non fermentable sugars, right?

It's not that far off given that the sacc rest of 160.

OG is just SG at a specific point in time (post-boil, pre start of fermentation.) FG is also just SG at a specific point in time (at end of fermentation.) So yes, whatever goes into solution in the mash affects SG and OG the same way.

If the SG drops after adding yeast, then yes there were fermentable sugars extracted during the mash. Many kilned malts already contain fermentable sugars, so conversion is not needed on those, they just need to dissolve in the mash.

Since the OP's mash did contain some diastatic power, there will be some creation of fermentable sugars. If the diastatic power is too low to completely convert the mash, then there is no easy way to know just how much of the sugar created is fermentable (lumping dextrins in with sugar.)

Brew on

 

[cantrell00]

OG is just SG at a specific point in time (post-boil, pre start of fermentation.) FG is also just SG at a specific point in time (at end of fermentation.) So yes, whatever goes into solution in the mash affects SG and OG the same way.

If the SG drops after adding yeast, then yes there were fermentable sugars extracted during the mash. Many kilned malts already contain fermentable sugars, so conversion is not needed on those, they just need to dissolve in the mash.

Since the OP's mash did contain some diastatic power, there will be some creation of fermentable sugars. If the diastatic power is too low to completely convert the mash, then there is no easy way to know just how much of the sugar created is fermentable (lumping dextrins in with sugar.)

Brew on

Gotcha. I think. Heh

 

[cutitoutdave]

Under aeration/oxygenation could also play a role... Make sure you're shaking or bubbling the cooled wort before pitching.

 

[NewJersey]

Why mash at 160?
I've never heard of anyone mashing that high