Bavarian Weizen Stuck

[pogolounge]

Hi, OG was 1.055, vigorous initial ferm for 2 days, after 2 weeks down to 1.025 and seems stuck, in a conditioned chamber held at 67. Any insight would be greatly appreciated. Thanks.

 

[Nateo]

Raise the temp 10* or so and it should start up again.

 

[Clementine]

How did you aerate the wort, I'm starting a theory that stuck brew after vigorous fermentation is due to poor O2 levels as the yeast get tried at the end. Theories I have tried/heard of:

Rousing with a spoon (probably not worth it after two weeks)
Energizer, have not tried this but apparently it works.
Raising temp, did this and it worked on a brew I did not even realize was stuck
rack on to cake of a good yeast, worked beautifully
add more yeast at high krausen, did not work
adding dried yeast have not tried it

Clem

 

[Malticulous]

Yes raise the temp, it the best thing you can do now. What was the recipe and yeast? How much yeast did you pitch?

 

[pogolounge]

Thanks everyone, it was a dried malt extract 10 gallon batch, pitched 2 tubes of white labs wlp380 into 71 degree wort, just went out to garage and dialed in new temp to raise 10 degrees. I will post back with results. Thanks again.

 

[Zen_Brew]

That's odd. 67 is already a warmer ferm temp for a hef yeast. 2 vials was a slight underpitch for 10 gallons, but nothing devastating.

Raising the temp a bit is a good start, though I don't know that I'd go to 77, maybe more like 72. Also a bit of energizer and/or nutrient in boiled and chilled water.

As to why it got stuck, Could be as suggested a bad under oxygenation. Are you sure fermentation temp and your measuring the gravity correctly? Does the temp drop at night maybe?

 

[Nateo]

Almost all of the yeast's flavor contribution happens in the first few days of fermentation. I've brought beers up to 20* over their fermentation temp to get them to attenuate fully without any issues with off-flavors from high temps.

By this point, even if there had been no aeration, I'd bet there are enough yeast in the wort to finish the job. Yeast become more active as temp increases, less active as temp decreases. Rapid fermentation increases temp. As initial fermentation drops off, temp drops, then the yeast floccs out. If the yeast has flocc'd out, it can't eat the sugar well. Rousing the yeast would be a good idea. You can do this by swirling the carboy.

 

[pogolounge]

I think I definitely had good aeration, used a stone for about 5 minutes until it foamed up real good, the temp definitely stays constant as I have a control system taking care of that, I will see if the increased temp gets things going and report back. Thanks again, I really appreciate the help.

 

[pogolounge]

Hey everyone, raised temp up to 75, still no activity. Do you think I should raise a little higher, wait another day at this temp or try and pitch some more yeast? Thanks.

 

[Nateo]

I'd give it another day or so, then raise another 10*. If you can swirl the carboy to rouse the yeast that would help too.