Stuck Fermentation: a Success Story

I brewed NB's Oatmeal Stout (all grain) a few weeks ago. Recipe is:

6.5 lbs Maris Otter
1.0 lbs Oats, flaked
0.5 lbs Simpsons Roasted
0.5 lbs Simpsons Chocolate
0.5 lbs Simpsons Dark

1.0 oz Glacier (@ 60 mins)

Nottingham yeast

NB estimates OG of 1.042, I was able to hit 1.051. Did all the usual stuff (chill, aerate, hydrate yeast, pitch, etc.). Yeast took off within 24 hours and went for about 5 days.

Took FG reading at day 14: 1.025 and very sweet. No fermentation activity whatsoever. This had never happened to me, so I looked and looked for ideas and did not find a fail-safe solution to re-start the fermentation, so I combined what I found. The beer is now at 1.013, is still bubbling slowly, and the samples tastes fantastic and has no signs of infection.

Here are the three things I added to the beer:

(1) LD Carlson Yeast Energizer: 1/2 tsp per gallon (2.5 tsp total)
(2) LD Carlson Amylase Enzyme: 1/2 tsp total
(3) Mini-mash of 1.0 lb 2-row pale malt in 32 oz of 140 F water for 15 minutes, cooled down to 75 F before pitching. Resulted in about 20 oz of wort. See also http://hbd.org/brewery/library/enzymes595.html.

I was worried that the mini-mash wort might infect the beer, but that appears not to have happened. Within 24 hours of adding these three things the fermentation was more active than the original. If this happens to me again, I will definitely repeat this method. No promises that it will work for you, but it's a winner in my book.

I hope you boiled that 2nd mini mash. Most grain is covered in Lacto and I don't think 15 min at 140 would pasteurize it.

You might be seeing a lactic fermentation happening...

Not trying to scare you, just something to look out for.

For what its worth, traditional stouts were probably sour anyway.

Glad it worked out. Was it the old Notty packages or the new vac packed ones?

I'd rather figure why it stuck then develop methods of un-sticking. I've been lucky and never had a stuck AG batch. Only hit the 1.020 wall with extracts.

PantherCity said:

I hope you boiled that 2nd mini mash. Most grain is covered in Lacto and I don't think 15 min at 140 would pasteurize it.

Click to expand...

I did not boil the mini mash because the purpose is to get alpha- and beta- amylase enzymes into the beer to break down the other sugars so fermentation can resume. Boiling would have denatured those enzymes. The link above explains it better than I can. I was worried about a possible infection, but it doesn't look like that is the case. Maybe I just dodged a bullet.

@samc: it was a vac-pac. I agree, I wish I knew why it did this in the first place. This has never happened for me, so I was baffled.

samc said:

I'd rather figure why it stuck then develop methods of un-sticking. I've been lucky and never had a stuck AG batch. Only hit the 1.020 wall with extracts.

Click to expand...

Get some iodine and some chalk and look up how to do a starch conversion test. May help in the future.