another stuck fermentation thread? yay!

You would think I wouldn't have to ask this with as many threads as there are about stuck fermentations. But I am.

Sooo I'm making a holiday beer which was brewed 10/20/12 which puts it on the yeast cake for 25 days now. Fermentation was nice and vigorous for a few days then calmed down. The SG was 1.072 @ 79° which makes it 1.074 after correction(?). I measured at 14 days and was getting 1.032. At 21 days, 1.03. So apparent attenuation seems to be < 60%. That seems awful!

I do have 1.5# lactose for 5.5 gallons of beer. I've seen a lot of numbers thrown around about points that lactose will add (lots of 1.004 SG for 1 gallon of water), but my gravity still seems fairly high..

Question is, should I be pitching more yeast or is my beer seriously done?

Fun facts:
- extract with specialty grain recipe
- Wyeast Irish Ale
- made a 1L starter after letting the pack fully expand after smacking
- yeast nutrient added to first .5L of starter boil
- fermented low-mid 60s

It probably wouldn't do much good to repitch, but you could try it and see how it goes. Does the beer taste right or is it too malty/sweet? You're looking at about 5.6% ABV (assuming your OG was 1.074); is that around what your recipe was estimating or is it low?

The ABV seems right, I estimated 5.5%. It IS sweet but not too sweet and tastes good if you know what you are getting. It's a milk stout modeled slightly after Left Hand but sweeter and not as smokey.

tiny bit of amylase can bring it down. start with 1/2 tsp and wait a few days

I'd try the amylase enzyme like tre9er suggested before putting more yeast in and see if it squeezes the last bit of FG out of it. Maybe on the next version of your recipe reduce the lactose to 1# and see if that falls more in line of what you were looking for.

tre9er said:

tiny bit of amylase can bring it down. start with 1/2 tsp and wait a few days

Click to expand...

can it go directly into beer? do I need to denature it?

You can just pour it in and let it do its thing. It'll break down the last of the remaining fermentable sugars to give the yeast something to nibble on. Amylase enzyme is cheap and you should be able to get a bottle from your LHBS for around $3.

Great! I'll pick some up this weekend and let y'all know how it turns out.

Thought I would update the thread. I bought some amylase last weekend and put a 1/2 tsp in and let it sit a few days. The FG hasn't changed so I guess I'll just have a high FG but the sweetness has mellowed out some. I'm going to bottle tomorrow making it a week since the amylase has gone in. Glad I have it and know about using it for the future.

Are you measuring your post-pitch gravities with a hydrometer or a refractometer? This can make a big difference as refractometers are no good after pitching yeast.

daksin said:

Are you measuring your post-pitch gravities with a hydrometer or a refractometer?

Click to expand...

Hydrometer

Gravity samples at 60°, right?

robotsNbeer said:

Thought I would update the thread. I bought some amylase last weekend and put a 1/2 tsp in and let it sit a few days. The FG hasn't changed so I guess I'll just have a high FG but the sweetness has mellowed out some. I'm going to bottle tomorrow making it a week since the amylase has gone in. Glad I have it and know about using it for the future.

Click to expand...

I'm surprised this didn't work. AE work pretty well. Too well, really. Here's my exeriment with them:

https://www.homebrewtalk.com/f163/escape-stuck-fermentation-mountain-ae-rescue-212926/

So I know this comment is a little late to help, but you did not experience a stuck fermentation. The lactose is "artificially" raising your attenuation.

So you added lactose, which like most sugars, has a pppg of 42. So:

1.5# x 42pppg = 63 extra gravity points
63 points / 5.5 gal = 11.5 per gallon

Your starting gravity was 1.074, but without lactose it was actually 1.063. Let's say you experienced an attenuation of 72%, which is mid range for Irish Ale yeast. Your beer should have ended up at 1.017 or so.
But if you factor back in the lactose, that raises your final gravity to 1.028. Considering that it's an extract batch, and a holiday ale that probably contains a good bit of specialty grains, a final gravity of 1.030 is not surprising.

So it really comes down to asking yourself why you used lactose if you wanted a high attenuation. Or why did you buy a holiday ale with lactose if you didn't want a sweet beer? I'm not trying to be a jerk or make you feel bad - just pointing out some things to consider for next time.

tre9er said:

Gravity samples at 60°, right?

Click to expand...

64°

kanzimonson said:

1.5# x 42pppg = 63 extra gravity points
63 points / 5.5 gal = 11.5 per gallon

Your starting gravity was 1.074, but without lactose it was actually 1.063. Let's say you experienced an attenuation of 72%, which is mid range for Irish Ale yeast. Your beer should have ended up at 1.017 or so.
But if you factor back in the lactose, that raises your final gravity to 1.028. Considering that it's an extract batch, and a holiday ale that probably contains a good bit of specialty grains, a final gravity of 1.030 is not surprising.

Click to expand...

I knew lactose would artificially raise the gravity, I just didn't know it was that much! So, thanks for the numbers and now I know for the future.

kanzimonson said:

So it really comes down to asking yourself why you used lactose if you wanted a high attenuation. Or why did you buy a holiday ale with lactose if you didn't want a sweet beer? I'm not trying to be a jerk or make you feel bad - just pointing out some things to consider for next time.

Click to expand...

Yeah, it's a milk stout holiday beer and I decided to raise the lactose, oops, so I knew it would be sweet and am not worried about the sweetness. But like I said in an earlier post, it's not too sweet despite the high lactose.