Fermentation Stopped at 1.030

I brewed up a malted milk stout on September 8, 2011. It was an all-grain recipe, and all went OK during brew day.

11.5lb Maris Otter, 12oz Brown Malt, 12oz Carafa I, 9oz Crystal 60, 9oz Crystal 120 in a 90 minute mash at 158 degrees F. Temperature held for the duration of the mash. 6 cups of malted milk powder were added for last five minutes of boil.

I had an OG of 1.073 (6 gallon batch) and pitched two packets of Safale 05 (rehydrated) (Use by date of 9/2012). The wort was also well aerated.

There was vigorous airlock activity less than 24 hours later and on September 13, 2011 I was already down to a gravity of 1.032.

Unfortunately, things seems to have ground to a halt since then. I was away on vacation for a couple of weeks so I kept the fermenter in the basement. On my return on October 3, 2011 the temperature of the beer was 59 degrees F and the gravity reading was 1.030.

I thought that perhaps the yeast had gone dormant due to the lower temperature, so I brought the fermenter into the house and placed it into a room with an ambient temperature of around 70F.

On October 5, 2011 the gravity reading was 1.029 and the beer was at 64F. I gave the fermenter a good swirl to try and rouse the yeast.

On October 7, 2011 the gravity reading was 1.029 with a temperature of 67F. I gave the fermenter another swirl.

Today, it's still sitting at 1.029 with a temperature of around 68F.

I am now at a loss as to what to do. The yeast don't seem to want to do anything more, despite raising the temperature and swirling the fermenter to put the yeast cake (which looked sizable) back into suspension.

Should I try adding champagne yeast? Should I just bottle? By my calculations, I should be getting a final gravity of around 1.018 so I am quite a way short.

Help!

I've never used malted milk before, but I have used lactose to make milk stouts. In those cases, the beer normally ended up with a FG in the 1.028-1.032 range due to the lactose being unfermentable. Also, I normally used 0.75-1lb for a 5.5gal batch. So I'm thinking that you are probably seeing the same thing, as I'm guessing that a good portion of the sugars in malted milk are probably unfermentable.

I'd say keg it and enjoy!

I have no clue what malted milk powder will do, and whether it contributed non-fermentables, but you did mash high, and that may be the reason for the high FG. I don't think adding wine yeast will do anything as all the simple sugars are already gone.

I think you are done.

The carmel/crystal malt and malted milk contain mostly (if not all) unfermentables, which would cause the high FG basically your only fermentables were from the base malt

Thanks for your replies so far.

Let's disregard the malted milk for the time being and just look at the malt bill. For a 6 gallon batch at 75% efficiency I should be looking at an OG of around 1.079 and an FG of around 1.020 - therefore, surely I am still coming up short?

I accept that the malted milk adds unfermentable sugars, but still - surely I should be getting closer to 1.020 than sitting at 1.030?

Thanks again for any suggestions.

So without adding 6 cups of malted milk, you should ferment down to around 1.020, that sounds correct. Then, on top of your 1.020, you are basically adding 1 cup per gallon of something that is, most likely, unfermentable. I think that would easily explain your high final gravity.

I also just checked the two milk stout recipes that I've made in beersmith (which doesn't account for the lactose addition in the FG calculation). Beersmith estimated an FG of 1.017 and 1.013 for each recipe. I measured FGs of 1.029 and 1.022, respectively, and the beer had definitely finished fermenting. So yes, I think everything you have seen with this brew makes sense.

All things equal, mashing at 158 is rarely going to get you 75%+ attenuation. Maybe with some yeasts, but those would be the stuff of legends.

That said, how does the beer taste? I've had some beers that stop at 1.030 or thereabouts that are mighty delicious. Don't mess with it if it tastes good. It's the beer that tastes good, not the FG.

I over looked the 158 mash temp all together, that's the problem, you had great use of alpha anamylese but they "randomly cut" starch chains which can make a lot of unfermentables, whereas beta anamylese create only fermentable sugars. That's a long story short with a lot left out, basically at 158* beta anamylese are close to being inactive, and the alpha anamylese are at there prime, but for your extended mash you got a good amount of fermentables but a lot of unfermentables, and that is why you have a high FG

A high OG doesn't mean anything except your water absorbed a lot of starch, the tempuratures are what makes a difference on how the starches are converted so your yeast can eat them, think of it as its impossible for us to eat a whole cow, but if we cut some of it to steaks we can eat it, but if its left as a quarter cow or whole side we can't eat it, so its left behind