Stuck fermentation?

[audiophool]

I got out my dusty brewing gear and tried my first brew in 16 years. Boy, have I forgotten a lot of what little I knew.

Anyhow, I have a German Alt in the fermenter for 10 days now. It had krausen and bubbling from the second 24 hours through about day 4 and virtually no airlock activity since then. The SG was 1.021 three days ago and today. Looks like fermentation has stopped.

The recipe included 5 lbs of Munich LME with 2.5 lbs of Munich malt that was mashed on the stovetop. It was a full volume boil and the OG was 1.050. Here's the rub. I mashed on an induction stovetop and used a digital thermometer probe. About 20 minutes into the mash I discovered that the thermometer registered about 30 degrees low whenever the burner was on, so instead of mashing at 158 degrees, I was actually closer to 190 - probably inactivating the enzymes.

I pitched yeast from a Wyeast 1007 (German Ale) vial at about 70 degrees. No starter.

From what I have read, the LME should have added about 36 points to the OG, so the other 14 points would come from my mash. Using that logic, I am guessing that the fermentables from the LME have been consumed since the OG has dropped by 29 points, and what is left is unfermentable starches and proteins from a failed mash.

My question(s) are

1. Is my logic correct on this?
2. Should I just let it condition and not try to do any more fermentation? Or
3. Would it help to pitch more yeast?
4. Would it help to add an amylase enzyme to break down starch, with or without pitching more yeast?

Thanks
Mike

 

[prandlesc]

My guess is that your analysis is right on in that there are probably no fermentables left. Assuming that's the case, no yeast addition will help. At least 1.021 should not be too sweet, but not as dry as the style guidelines would suggest.

Best of luck.

 

[Complete_Amateur]

I got out my dusty brewing gear and tried my first brew in 16 years. Boy, have I forgotten a lot of what little I knew.

Anyhow, I have a German Alt in the fermenter for 10 days now. It had krausen and bubbling from the second 24 hours through about day 4 and virtually no airlock activity since then. The SG was 1.021 three days ago and today. Looks like fermentation has stopped.

The recipe included 5 lbs of Munich LME with 2.5 lbs of Munich malt that was mashed on the stovetop. It was a full volume boil and the OG was 1.050. Here's the rub. I mashed on an induction stovetop and used a digital thermometer probe. About 20 minutes into the mash I discovered that the thermometer registered about 30 degrees low whenever the burner was on, so instead of mashing at 158 degrees, I was actually closer to 190 - probably inactivating the enzymes.

I pitched yeast from a Wyeast 1007 (German Ale) vial at about 70 degrees. No starter.

From what I have read, the LME should have added about 36 points to the OG, so the other 14 points would come from my mash. Using that logic, I am guessing that the fermentables from the LME have been consumed since the OG has dropped by 29 points, and what is left is unfermentable starches and proteins from a failed mash.

My question(s) are

1. Is my logic correct on this?
2. Should I just let it condition and not try to do any more fermentation? Or
3. Would it help to pitch more yeast?
4. Would it help to add an amylase enzyme to break down starch, with or without pitching more yeast?

Thanks
Mike

If you are not happy with it as is, I would go with #4, adding amylase. You should not need to re-pitch yeast, and yeast alone will not help. See this.

Excerpt:

"If a malt contains significant unfermentables (and most do - more or less), then the beer will only ferment down to where it has used up all of the fermentable sugars, and stops there. SG values all the way up into the 1.020's can be a result of this problem. Such a problem, in the case of extract brewers, is NOT the fault of the brewer, and the ferment is stuck at that point.

This kind of stuck fermentation can be dealt with by the use of enzymes. They can be added when pitching yeast, or when they notice the fermentation seems to be stuck at a higher than expected SG. The enzymes will slowly break down the unfermentable dextrins and complex sugars, into fermentable sugars. This will result in the fermentation resuming, and help to lower the SG to a more acceptable FG value.

NOTE: Both alpha amylase, and the mixture of alpha & beta amylases will work in this case - but beta amylase containing enzymes will be superior in this situation."

 

[bleme]

I've seen guys on here add amylase and drop below 1.000 so proceed with caution. If it were my beer, I would give it a couple more weeks, bottle, and focus on my next brew.

Speaking of which, I have had pretty good luck mashing in my oven. Some guys just preheat their oven to 170F and turn it off. My oven doesn't hold that well and the thermostat is off so I put a probe in my mash with an alarm set for my target and turn it on/off as needed. It is a lot more steady and even than trying to do it on the stovetop.

 

[audiophool]

I was going to try the amylase just for grins, but my local home-brew shop was out, so it will just sit in the primary until I have time to keg it.