High Than Expected FG

[bradford0113]

I brewed Yooper's Dead Guy Ale clone two weeks ago. The recipe can be found here: https://www.homebrewtalk.com/f66/dead-guy-clone-extract-ag-see-note-25902/

I brewed the all grain version as a full volume BIAB. Mashed at 158F for approx 75 minutes. My expected gravities were 1.066 OG and 1.017 FG. I missed the OG a little bit as I only had 1.060 going into the fermenter where I pitched a nice slurry of bottle harvested Pacman yeast which I cultured from 3 bottles, stepped up 3 times, and then made a 1.5L starter from that just before brew day. Fermentation temp was approximately 60F.

This brew has now been sitting at gravity of 1.020 for about a week and it's not dropping any further. Even though I was expecting a FG of 1.017, I figured it would actually be a lot lower than that because of the fact that I missed my target gravity.

I'm a little concerned because I was expecting the gravity drop to be 1.066 to 1.017 (6.6% ABV) but right now I am only getting a drop of 1.060 to 1.020 (5.2% ABV).

I know there could be a lot of factors contributing to this situation such as mashing too high (more unfermentables), the viability of the bottle harvested yeast, and the fermentation temp.

Anyone have any thoughts on this? My biggest concern is bottling this as-is and ending up with bottle bombs!

 

[brewprint]

From what I understand; your mash was at least 4 degrees too high. I did the same thing on Saturday which was my first BIAB. My SG was low and my guess is that my FG will be high. Hey I'm a rookie so I don't know if that's why but it sure sounds like it. Unfermentables are created with that high of a mash.

 

[brewbama]

You mashed high in the alpha sach range so your FG "suffered". As long as you use plenty of hops for balance that's not necessarily bad.

As you alluded to: You'll get a sweet malty beer with thicker mouth feel than you would had you mashed at a lower rest temp. If doing a single infusion mash 150-154*F has been my go-to temp range. Lower for more fermentable wort (lower FG) resulting in drier beer, higher for less fermentable wort (higher FG) resulting in maltier beer.

 

[BigFloyd]

Looks like you're done at 1.020. I brewed this same recipe and mashed at 154*F. That 4*F can make quite a difference.

 

[TungstenBeer]

Do you have any temp control for fermentation? I'd kick it up 5 degrees and see if any activity shows. Alternatively (or in addition), you can swirl the fermenter first to make sure it's done.

I would think it's done though. 158* is really high for mashing this style. Ironically, I just read a thread where Yooper said her brews tend to over-attenuate , so maybe that's why she mashes higher. Unfortunately, if you follow the same procedure but take out the high attenuation, you end up at higher-than-expected FG.

 

[bradford0113]

The reason I mashed at 158F is because Yooper had posted in the recipe thread that that is the temp she likes to mash this beer at. I suppose my thermometer could be off slightly too so I may have even mashed a little higher.

I'm going to assume that this beer is done at 1.020 and proceed to bottle in a week or so. I'm sure it will still be good but different than what it was supposed to be.

 

[bradford0113]

Do you have any temp control for fermentation? I'd kick it up 5 degrees and see if any activity shows. Alternatively (or in addition), you can swirl the fermenter first to make sure it's done.

After signs of active fermentation were complete (about 5 days), I moved the fermenter from 60F ambient temp environment to 68F ambient temp environment and also swirled it. Checked the gravity three days later and saw no changes. It's got to be done.

 

[TungstenBeer]

Yup - I would definitely say it's done.

 

[stpug]

I know there could be a lot of factors contributing to this situation such as mashing too high (more unfermentables), the viability of the bottle harvested yeast, and the fermentation temp.

Anyone have any thoughts on this? My biggest concern is bottling this as-is and ending up with bottle bombs!

You've pretty much nailed it as to why your gravity stopped shy of your expectations, BUT this is part of the learning process and an important one at that. You now have a good idea of how pacman yeast will perform in a beer consisting of ~12% crystal malt with a high dextrinous mash temp. Next time, hit your OG and drop that mash temp, and then you'll have a second data point on the performance of pacman and mash temp. IMO, this is pretty "par for the course" when dealing with a new yeast. I will often times revisit recipes that used specific strains of yeast to have a better idea of how they'll perform in a future batch based on mash temp and unfermentables (roasted malts keep throwing me for a doozy [i.e. high FGs] since I rarely brew dark roasted beers). It's amazing that the chico strain is not very affected by high mash temps but others (like nottingham) are; chico might have a 1-2 point difference in FG from 150 vs 158 mash temps, whereas notty would have like a 5 point difference in FG from the same mash temps.

As for bottling: Give the beer another week at a higher room temperature (no need to rouse or mess with it) and take another gravity reading. If it's stable then bottling should process as normal.

 

[klaggy]

My first thought and impression was your mash temp at 158.... And would account for your higher than expected gravity... 153 is about the ideal temp range as a rule of thumb... That temp range unleashed a bunch of unfermentable dextrine of of the starch molecule. Giving you much larger body.
All mashes I do never goes over 155 for that sacc rest. And nearly always hit expected starting gravity and finish at or within a point of expected finish.

 

[BigFloyd]

I suppose my thermometer could be off slightly too so I may have even mashed a little higher.

That's quite possible. I've got a floater thermometer (which I no longer use) that is a whopping 7*F off.