Much higher attenuation than expected

[Stevesauer]

Hello. Brewed a milk stout last week. Grain bill called for roughly 17 lbs of grist. I performed a single infusion mash, held at 152* for 75 minutes. I added one pound of lactose with 10 minutes left in the boil. SG was 1.094.
Beersmith estimated my FG at 1.028. 8 days into primary it's at 1.016! Clearly way more attenuation than expected. I used 2 packs of S-04 English ale yeast. I rehydrated and pitched into 65* wort aerated for 30 minutes with an aquarium pump. Fermentation temp was held at 66* via a Johnson A419. By the next morning, this yeast was rocking and rolling. The blow off was constant. When it finally subsided after about 72 hours, I lost about 2 gallons to blow off. My question is, why did I achieve such high attenuation? If the mash temp isn't the culprit, what is? Is this yeast this voracious? I've read it can be. Also, lactose is not fermentable, correct? This being the case, did I overpitch based upon a SG of 1.094, when in reality the fermentable portion of the wort was closer to, say, 1.080? I'm confident the beer will condition fine and the alcohol heat will subside, I'd just like to learn from this experience. Any input is welcomed. Thanks!

 

[m00ps]

mashing at 152 for a milk stout isnt really ideal. Im wondering if on top of that, whether your thermometer was off and you mashed like a 148 or something. That might explain it a bit

but what really doesnt make sense is the alcohol content of that. S04 should not be able to tolerate those levels. Do you knwo if anythign weird couldve happened to either hydro reading? Does the samples right now feel very thin bodied?

also wondering if brett made its way into it...

 

[Stevesauer]

You're right. 152 may be a little low. I forgot to change my beersmith settings for full body. I ended up with medium body temps. Samples don't feel thin bodied at all. As far as brett, it's only been used once in my homebrewery. Currently in secondary on an IPA.

 

[sweetcell]

S-04 isn't ideal for high gravity beers, but it will go that high under the right conditions. you could have met those conditions.

doubtful that it's brett. brett is slow, it won't have chewed that much in just 72 hours, certainly not unless you've pitched a massive amount of brett.

how confident are you in the accuracy of your hydro?

i wouldn't trust BeerSmith for FGs, much. 1.028 seems high for that recipe. let's say that 1.024 is a more realistic estimate, but you mashed lower than prescribed so that drove you lower, the S-04 got extra happy, and your hydrometer (or your reading of it) is a few points off... boom, you're at 1.016.

in the end it's just a number. if it tastes and have the mouthfeel you're looking for, then you've been successful

 

[Stevesauer]

Appreciate the insight fellows. I'm confident in the hydrometer reading. Never tested its accuracy in distilled water however. Perhaps it's a point or two off. Perhaps, as has been suggested, my mash temp was a little low. Next time, I will certainly mash higher. This being my first time working with this particular yeast, I was surprised at its ferocious fermentation. I've never lost so much to blowoff. Guess it was the perfect storm of slightly low mash temp, a highly fermentable wort, and a very hungry yeast.

 

[Calder]

mashing at 152 for a milk stout isnt really ideal. I'm wondering if on top of that, whether your thermometer was off and you mashed like a 148 or something. That might explain it a bit

but what really doesn't make sense is the alcohol content of that. S04 should not be able to tolerate those levels. Do you know if anything weird could've happened to either hydro reading? Does the samples right now feel very thin bodied?

also wondering if brett made its way into it...

Don't get the guy worried about Brett. Brett had nothing to do with it. With a healthy sacc pitch, Brett wouldn't show itself for a long time. With a healthy pitch of yeast, nothing else would have done the hard work either. It would take time for anything else to build up its colony to make any impact on the sugars, not happening in 8 days.

I would have thought S-04 was man enough for that level of alcohol. However, I'm not sure I have ever used it, so I don't speak from experience. I've not heard anything about it being a low alcohol tolerance yeast. I figured it would be good for 10 to 12% (I guess he is over 10% right now).

I think I agree, mash temp is probably the culprit, and he may have been in the 140s not 152. Time to check the thermometer.

i wouldn't trust BeerSmith for FGs, much.

I wouldn't trust it for FGs at all. It takes no account of fermentability of the wort, and just uses a percentage attenuation it has associated with that particular yeast. Create recipes with 100% Simple Sugar, and another one with 100% Lactose, and I would expect it will give you the same FG for the the same OG. I only have BS 1.4, but I suspect it is the same with BS 2.2, or whatever the current version is.


After all that, I would expect 1.016 will produce a pretty good Milk Stout.