Pilsner fermentation -slow or stopped?

[the_great_okapi]

Hi guys, could do with a little advice please!

I made a batch of Bohemian Pilsner a while ago using a triple-decoction mash, and I am not sure if the fermentation is really finished, stuck or just incredibly slow.

I followed the decoction procedure in Ray Daniels' book which is mostly at the low end of the mash temperature (63 C), and may have produced a beer that was more full-bodied. Nevertheless, I used Wyeast Czech Pils yeast, which should have finished the job in the time it has had.

It fermented at 10-15 degrees C for two weeks, from SG 1048 to 1020, and I then racked it to demijohns and shoved them in the shed (4-10 degrees) for the last 3 1/2 weeks. There was some yeast transfered during the racking.

The SG is still around the 1020-1018 mark, pH around 5. It isn't overly sweet, or overly sulphorous, but there are still bubbles occasionally forming in the demijohn (not airlock) suggesting the yeast are doing something.

Do I keep it in the warm, bung it back in the shed for longer, or take a chance and bottle it? I could do all three but I don't want to waste any. That would be a crime.

If anybody has done something similar I would like to hear what you did!

[Aleman]

Unless your thermometer is out mashing at 63 will produce a very fermentable wort, particularly with a triple decoction (More starches are released)

If you pitched Sufficient yeast then it should have fermented to FG in those two weeks, or at least to 1/3 gravity, then the period spent in the colder temps should have got it down to FG (Plzen use a 12 day primary, 12 week lager schedule).

When you took your decoctions you should have just removed the grain (Using a sieve), allowing as much liquor to drain as possible, the reason for this is that the enzymes are in the liquor, leaving the liquor behind leaves the enzymes behind, and therefore they don't denature. I am seriously wondering if it is your decoction technique that is to blame here . . . . it is a possibility.

I would take one of the demijohns and move it into the warm . . . say 60F give it a gentle swirl to resuspend the yeast, and see if fermentation restarts (CO2 that is dissolved in the beer will come out of solution, so fermentation apparently restarts . . but see if fermentation proper restarts. If it does, you've just started the lager process too soon. . . . If not, you messed up your decoctions

[the_great_okapi]

Yes, I didn't use a sieve so perhaps my decoctions were a little too thin.

I will give them a swirl and see if I just lagered too early. The krausen started to fall back in so I thought that would be a good time to begin lagering. Maybe not. High carb, low alcohol could be it.

Has anybody tried adding amylase later in the fermentation process?

Thanks for the advice.

[Barley Water]

I agree with Aleman regarding his comments about decoction technique. The other question I would have though is, how much yeast did you pitch? I used to have all kinds of problems with low attenuation doing lagers until I figured out that you need to pitch a Massive amount of yeast (at least compared to what you are used to doing with an ale). The other problem you run into with under pitching is that you stress the yeast. Stressed yeast produces pheonols, esters and other nasty tasting compounds that you don't want in a lager.

Anyhow, take Aleman's suggestion and try letting the temperature go up in the fermentor to get things going again. Be warned however, you may have some problems with off flavors due to stressed yeast and possibly higher than optimal fermentation temperatures. That said, the beer will still taste ok and you can be drinking it while you brew your next attempt. I would caution against adding amylase, I would be more inclined to repitch with neutral ale yeast, at least the resulting beer will still be drinkable.

A couple of other things to watch for are, as usual, good sanitation and for sure, heavily oxiginate the wort before pitching the yeast, preferably with pure O2. The more healthy yeast you use, the quicker the fermentation will start and the quicker and more completely it will finish making for a better tasting beer. Good luck to you, once you get lager beers down pat, all your beers will improve because lagers force good technique to be successful (especially yeast handling).

[the_great_okapi]

Thanks guys, the advice is much appreciated. It is my first lager, and I will try and take more care next time.

The demijohns are showing signs of fermentation at room temp, so it looks like the yeast were underpitched or I lagered too early.

All the best