Stuck fermentation?

[danb35]

Short version: I brewed a batch of BierMuncher's Blue Moon clone (https://www.homebrewtalk.com/f71/blue-balls-belgian-wit-blue-moon-clone-24978/) three weeks ago, using US-05 yeast as recommended elsewhere in the thread. Starting gravity was 1.038. The gravity has been stable at 1.020 for at least the last two weeks. What to do?

Longer version: This is my third batch, and it was a lot of "first"s. First all-grain, first BIAB, first using my eKeggle, first no-chill, and first doing any kind of water chemistry adjustment. I may have changed too many variables at once here. I know I had some trouble with temperature control during the mash, but I'm not sure if that might be causing my problems--I recall that high mash temperatures can result in more unfermentables in the wort.

I started with 8 gallons of distilled water (couldn't find a RO kiosk), and added 1.5 tsp calcium chloride per https://www.homebrewtalk.com/f128/brewing-water-chemistry-primer-198460/. I modified BierMuncher's recipe by adding 2.6 oz (just under 2% by my math) of acidulated malt, also per the primer thread. Heated the water to 155 F per my temp probe and added the grain (4.5 lb. Marris Otter, 4.5 lb. flaked wheat, 2.6 oz. of the acid malt). At this point, the temperature rose to 159 F and took quite a while to come down. Mash pH after about 15 minutes (cooled to 30C) was 5.25.

After an hour's mash, removed the bag, let drain, squeezed a little bit, and brought to a boil. Boiled for an hour, adding the hops (1 oz EKG) 20 minutes in. Added the coriander and orange peel (.75 oz each) with 5 minutes to go. Drained into a cube and let sit overnight.

The next afternoon, I poured the wort from the cube into a 6.5-gallon carboy using a funnel. Pitched the yeast dry at about 75 F, then wrapped the carboy in a wet towel and pointed a fan at it--this seemed to bring and keep fermentation temperature to 68-70 F.

After a week, there had been no visible signs of fermentation--never any active bubbling of the airlock, no notable krausen, etc. However, the gravity had dropped to 1.020, so obviously fermentation had been taking place. I chalked it up to just getting a slow start. However, it's now two weeks later, and there's been no change in the gravity.

So, given the long version of the story, what should I do? I have another packet of yeast (though it's Nottingham, not US-05) that I could pitch if that would help. Or should I just bottle/keg it and accept that the ABV will be lower than intended (which isn't the end of the world)?

 

[Gduck]

At this point it seems like the yeast might have not been in the best condition and crapped out early on you. If you haven't seen any further change below 1.020 I'd say one way or another most of that yeast has dropped out and stopped working.

I'd probably pitch that other pack of yeast you have. You could try rousing the yeast (gently rock your fermentation vessel to try and get the yeast back in to suspension), but personally, if they quit that early on such a low gravity beer I'd just toss in another pack of yeast.

***EDIT*** Maybe I should have read it all, I blame it on the lack of coffee and two crying children. At a mash temperature of 159F you'll have denatured some enzymes there and created some sugars that are going to be unfermentable by the yeast. So there's a good chance that adding another package of yeast won't significantly reduce your gravity. It may go down a couple more points, but I'm guessing you have a bunch of unfermentable sugars in there.

 

[duboman]

Something is wrong here....

It is basically impossible for your water temp to rise after adding the grain to mash unless your grain temperature was hotter than your water which I highly doubt

The mash temp will typically drop 5-10 degrees from the strike which means, assuming your thermometers are calibrated, you actually mashed lower not higher. At this point you need to question the accuracy of your measuring device.

The low OG is probably due to a poor crush. You also need to make sure your hydrometer is calibrated and that you corrected the readings for temperature. Also, if you used a refractometer for FG then take a hydrometer reading as the former probably gave you an incorrect reading

If all the above is done then raise the temp and rouse the yeast and see if it drops over a few days

 

[CraptainWirtz]

Where did you take your temperature reading of your strike water? At the top of the water? It's possible you may have had a temperature gradient where the water at the bottom of the keggle, nearest the burner, was much hotter than at the top. When you added grain (and stirred? Dunked?), this gradient could have disappeared and led to your apparent temperature increase.

 

[BanginBanjo]

If your mash temp started off at 159F, that's probably your problem. If you didn't vigorously stir the mash or add ice to get the temperature down, you probably have too many unfermentables in there and adding more yeast won't help.

Although, as stated above, if you heated your strike water to 155F, it's going to go down when you add your grain. In my experience, my strike water drops about 10-12F after adding the grain.

I would recommend getting a more reliable (and calibrated) thermometer and making sure you check the temperature at multiple points in the mash, since hot/cold spots happen. Also, if your mash temperature is several degrees high, you can add a few ice cubes and stir it up to drop it quickly, just be careful and add one or two at a time so you don't cool it down too much.

As for your beer now, if you do indeed have too many unfermentables in your beer, then its FG is about what it's going to be. In case the mash temp was actually lower, you should still try to warm it up a bit and shake it up to rouse the yeast in case they decided to quit working on you. If that doesn't work you can still try pitching more yeast but it might not help any. You can still drink it the way it is, but it's going to be on the sweet/syrupy side with low alcohol and probably won't resemble a Blue Moon much at all.

 

[danb35]

The temperature was taken with the temp probe for my PID controller, which is at the bottom of my kettle. I do trust the temp reading; it's right where it should be at a boil. I suspect a temperature gradient, as otherwise physics wouldn't allow the temperature to increase when adding a quantity of lower-temperature grain. For future use, I'm planning on adding a pump to recirculate the wort, but of course that doesn't help this batch.

The OG was exactly what was expected with the recipe, so no problem there. If the problem is unfermentables in the wort/beer, what are my options? I see three:

1. Go ahead and bottle/keg it. It'll only be 2.4% ABV, and might be overly sweet (but how sweet would the unfermentable sugars be?).

2. Add some DME--this would add fermentable sugar, and presumably increase the ABV, but wouldn't do anything about the unfermentable stuff already in there.

3. Dump it--rather not do this, but I guess it's an option.

Thoughts? Thanks for all the input so far.

 

[Gduck]

Taste a little of it and if the flavor isn't bad bottle it up. Might be weak, but hey, it'd make for a nice lawnmower beer that you can power back a few of without falling asleep on the couch.

 

[danb35]

The smell is good, the taste not bad (given it's warm and flat). I went ahead and kegged it--figure at least I can see how it'll be cold and carbed before I decide to dump it. After all, not much work to siphon it into a keg and hook up the gas. Next up, a pump so I can recirculate the mash and avoid this problem in the future (I hope).