US-04 poor attenuation

OK - Here are the details. Brewed 6 gallons of a slightly modified version of BM's Black Pearl Porter on 2/14/11 as follows:

8 lbs. Maris Otter
1 lb. Crystal 40L
.5 lb. pale chocolate malt
.5 lb. chocolate malt
1 lb. flaked oats (minute oat meal)
.25 lb. black patent
1 oz black barley (a la Ed Wort's robust porter)

1 oz 4.5% Fuggles at 60 min (14 IBU)
1 oz 4.5% Goldings at 30 min (11 IBU)

Mashed 60 minutes at 156 degrees. Double batch sparged with 180 degree water. Ended up with a post boil OG of 1.053. This was an efficiency of 78%.

Pitched a packet of re-hydrated US-04 and fermented it at 63-64 degrees. SG on 2/24/11 was 1.024. Took it again on 3/1/11 and it was still at 1.024. This is an apparent attenuation of 55% which seem low even for this yeast.

In between the last two SG readings I moved it to a warmer area and got the temps up into the low to mid 70's and swirled the fermenter a few times, but this did not change anything. Taste was okay on 3/1 - still green, but nothing unusual.

I was looking to brew a slightly sweet session porter without having to add lactose, etc. That was the purpose of the 156 degree mash. I am not concerned about the FG if it indeed is done fermenting and not just stalled out. I am in no hurry to bottle, and will be letting it sit for at least 2 more weeks.

My question is this. Is the high FG due to the higher mash temp? I thought that it would raise the FG by a few points, but I still expected it to be below 1.020. I haven't used US-04 much (Notty is my main yeast), but I selected it because I didn't want a dry porter. I tried searching mash temps and fermentability, but couldn't find any real answers. ( I realize that there are too many variables to just say this mash temp = this attenuation with this yeast.) Do my specialty malts play into this as well?

I have been brewing for almost two years, and the area of mash temps, specialty grains and yeast selection vs. attenuation is something that I am still struggling with.

Thanks in advance.

Warm it up a couple degrees and see if the fermentation picks up again?

Brian

Benthic said:

Warm it up a couple degrees and see if the fermentation picks up again?

Brian

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Already did that.

Hmmm...did you aerate the wort? How old was the yeast you pitched? (I'm just guessing here)

I've got a batch going right now with US-05. It fermented like mad for two days and then it stopped--and then a day later it started up again all on it's own. I'm not sure why.

Brian

FWIW; it appears between the high mash temps, crystal, and dark grains, this may be it. If you have used 'beersmith' plug in the recipe and I would bet it will give you a high FG. You are doing everthing you can by warming, swirling, and leaving for another 2 weeks. This isn't the yeast issue, more likely recipe..... typically US04 ferments dry when mashed at a lower temp and more fermentable sugars

Its not the mash temp or the yeast or the recipe causing your high FG. Benthic is asking the right questions.

Hang on a minute. Did you pitch US-05 or S-04?
What color was the packet? Red, or blue?

They are two completely different yeasts with different attenuation, and there is no such thing as US-04.

S-04. Sorry for the confusion. I did aerate well before pitching. The yeast was just bought from BMW and well within the use by date.

funkswing said:

Its not the mash temp or the yeast or the recipe causing your high FG. Benthic is asking the right questions.

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This is too absolute a statement, in my opinion. Mashing at 156 combined with a grain bill of more than 25% specialty grains would tend to lead to a higher final gravity. Benthic's questions about yeast health are on target, too, but that doesn't mean that mash temp and recipe aren't also in play.

S-04 can get stuck sometimes in my experience because it flocs out really well and forms a very tight cake on the bottom that is practically like glue. It is actually kind of well known for floccing out early. So just shaking the fermenter might not even do anything to get the yeast back into suspension. If you REALLY want to make sure it's done, get some kind of sanitized spoon or something and literally stir that yeast up again. Also warming it up into the 68F range wouldn't hurt at this point.

If that doesn't work, try tossing in some amylase to break down any remaining starches into fermentables. That should dry it out a couple of points.

Pappers_ said:

This is too absolute a statement, in my opinion. Mashing at 156 combined with a grain bill of more than 25% specialty grains would tend to lead to a higher final gravity. Benthic's questions about yeast health are on target, too, but that doesn't mean that mash temp and recipe aren't also in play.

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What I was saying is that if I brewed this recipe with the same mash schedule I would be concerned about the high FG, too. Because none of the parameters listed in the OP seem to be the culprit. Its obviously a poor fermentation result. So the yeast health, pitching rate, rehydration v no rehydration, confidence in the actual beer fermentation temp, or aeration would be where I would start looking into.

The whole 156 F mash temp is fine, which produces more of a full mouthfeel than totally F-ing up your FG, especially in a beer with this low of an OG. Sure there are more dextrins in the wort b/c of the higher mash temp, but that would not solely cause your ~55% attenuation. If so, Lagunitas would not be such a successful brewery (they generally mash b/w 156 - 160 F).

There is not enough info in the OP to determine why the yeast crapped out on the beer. If I had to suggest anything to try to lower the FG it would be pitch a small amount of fresh yeast (< 1/2 dry yeast package) and see if anything happens, but I really think you should take this batch as another part of the learning curve. Benthic is pointing you in the right direction as to the questions you should be asking yourself about your process.

Thanks everyone for your replies. I have done nothing different with this beer than I have in the past 2 years - chill, aerate by pouring the wort back and forth between two ale pails 3-4 times, pitch what I believe to be health yeast in the proper amount (rehydrated dry yeast, or an appropriate sized starter). (I have had a couple of beers that seemed to stall at 1.020 and then "pick it up again" after a week or two and finish 5-6 points lower. Most notably this happened twice with an amber/red ale that uses a pound of C-120. I used US-05 with this once and Notty the other time.)

Last night I boiled 5 oz of sugar in a cup of water and dumped it into this fermenter to see if that would kick start anything. I also raised the temp to around 66 degrees. This morning the airlock is bubbling, so there are yeast working (on at least the sugar). I will give it some more time before taking another SG reading.

As I said in my first post, I am not overly concerned with the FG. I am just trying to understand why it is what it is.