Cold Fermentation method keeps failing me (stalling)

[Owenbräu]

I've never understood the anaerobic starter method. All you are doing is making a mini-yeast cake, complete with the same generational and performance limitations as re-pitched yeast. They will be more active and have more cells than simply trusting a vial of store-bought yeast, sure, but you must treat it like re-pitched yeast when you go to ferment a batch.

Be sure to find a way to get oxygen into your starter. There are plenty of threads on building a stir plate yourself, or just get an aquarium pump. Load up the starter with nutrients and get the yeast as healthy as possibly. Sometimes you will have to step-up multiple starters to get the proper amount. A fairly common method is to go 2L->4L->pitch. Brewers friend has a nice calculator for stepped starters. http://www.brewersfriend.com/yeast-pitc ... alculator/

Also, don't worry about crashing out your starter. You are already at 10C, which is plenty cool for lager starters. If you let the starter go, then you will see that the yeast will flocc out on their own. The colder you get the yeast, the deeper they will go into a dormant state. Cold crashing is really only for long-term storage or when you are running behind and need them to flocc out quickly. You may also be selecting/programming for cells that go to sleep more quickly once they detect temperature drops, which they will also do once you start dropping the temperature in your batch of beer. This takes more than once generation, but you can train your yeast.

Temperature often fixes may issues with stalled or underperforming fermentations. Don't be afraid to raise it up 8-9C and drop the temperature no more than 1C per day. Also, adding fresh yeast at spundening will help out the old tired cells and keep you driving towards EVG.

[Weizenberg]

It extremely difficult to say how much oxygen is in the wort unless you have a DO meter. Surely, you can estimate it, but then you need to be prepared for inconsistent results as trade-off.

For cold fermentations 8-9 mgl of oxygen is the recommended range. I use cheap agricultural Venturi tubes to aerate my wort. They do a very good job mixing the gas.

Although it may not explain your attenuation problem, Dunkels are often fermented using the warm schedule.

What were your temperature rests when mashing? If you do a 100% Munich malt Dunkel, then you need to adjust your rests accordingly. Munich malt can take much longer to convert and often a munch more intense mashing schedule is selected. I'd adjust accordingly and extend my rest times by 30-50 % when in the amylase range.

Hope this helps

[Brody]

[Nick_D]

[Nick_D]

[Owenbräu]

Tasty dunkel recipe about half-way down:

http://www.weyermann.de/cz/faq.asp?umen ... &sprache=1

[Nick_D]

[Weizenberg]

[Weizenberg]

[Nick_D]

PROGRESS REPORT:

I've been away a little while, propagating yeast, getting myself organised for another run at this. I just transferred my current beer to spunding keg, and so far, so good....

Since my last attempt, I've gone back to try WLP833 again. Had an old sample in the fridge that was 1 generation old, so with the help of a friend who works in a biology lab, I cultured up some fresh yeast in malt agar, and built up my supply from there. After several large starters, which I supplied constant aeration to via an aquarium pump and 2 micron stone, I gathered 350 ml of dense yeast.

I pitched this at 5.5C (42F) into a lodo Märzen (O.G 1.051, FFT 1.010), and aerated for 12 hours with the aquarium pump, instead of using pure oxygen. I realise that 12 hours is overkill, and possibly risked oxidation of the wort, but I wanted to completely rule out insufficient oxygen. Without a DO meter, I think maybe pumping air is a safer option than pure oxygen ?

Fermentation kicked off quite rapidly. after letting it rise to 8C over 48hrs, the ambient of the fridge was holding a chilly 6.6C, a difference of 1.4 C. A day later and I had reached 50% apparent attenuation and started to cool. I've never reached 50% so fast. 2.5 days later and I was at 1P above expected final gravity. Again, this is very fast compared to my other beers that failed, so something different is going on for sure ! Also, the fermenting wort tasted amazing, whereas my previous attempts have been a bit acetaldehyde'y.

temp was 6.5 C when I transferred to spund, and the airlock was still bubbling strong, and plenty of thick foam on top of the beer in the FV too. Looked like plenty of yeast in suspension as I siphoned. Seated the keg lid with 0.5 Bar of pressure after purging the head space of the keg (probably about 1000ml head space, as I was a bit short this brew). Pressure is slowly building on the gauge (up to 0.65 bar after a few hours).

So, it's got a while to go yet before I can call it a success, but it's looking good, and is definitely progress. I wanted to report that much at least, so that everyone who has chimed in with their help can know it's not all been for nothing! I really appreciate it, thank you.

I have a theory. I wonder if i had residual SMB in the other brews, which competed for the oxygen I was trying to get to the yeast at pitching. Aerating for 12 hours would have knocked any SMB out of action. Just an idea.Thoughts?

I will update when I have more news ! Stay tuned. Thanks again, and sorry for the mega post.