Interesting Lager Predicament: Too fast?

Yeast don't follow your schedule. I'd bump the temp up for your diacetyl rest now, unless you have tasted the beer, detected no diacetyl, and want to roll the dice that none is forming.

Also, I recommend not starting lager fermentations warm. I start a couple degrees below the target fermentation temp and warm up to the fermentation temp (usually 50F). People claim to make great lagers with warm starts, but it's not for me.

 

What was your expected FG? How long has it been in the fermenter? Even if you are very close to FG, there would be no harm in moving your fermenters to 65* for 2-3 days. Afterwards, I would still give it some more time at preferred fermenting temps. Shoot for AT LEAST two weeks total (including ferment and d rest). Some might disagree with me there.

Also, there is always the chance that your beer was free of diacetyl right after fermentation. All reports of WLP940 say that it is super fast and super clean. Plus, an ambient temp of 52* puts you at or over the max recommended range during peak fermentation, so, the yeast might have reprocessed the diacetyl by then as a result.

Only other thing that stood out to me was pitching at 60*. If you have the ability, I would suggest pitching at or just below the recommended range next time.

EDIT: beaten by VikeMan

 

This should be in all caps on each package of yeast.

I think as yeast come into the world they are issued a manual titled "1001 Ways to Befuddle a Homebrewer". What we call the lag phase is actually the conspiracy phase where they huddle together and decide which trick to play on the brewer ("this dude's on BA, let's give him something to post about!). Just my thoughts.

 

Not to be semantic, but CO2 is most certainly odorless.

 

Lagers do not have to take 14 days to reach FG. Mine take 6-7 days, a couple of days longer for a 1.085 Doppelbock.

You should start the D- rest with a few gravity points left. At 1.011 the yeast might be dropping out. If you taste no Diacetyl, good.pull a sample and swarm it up, taste warm as that will bring the diacetyl out. Pitch cold as Vikeman says. I pitch at 45F, ferment at 48-50F.

WLP-940 is the cleanest lager yeast I have used. For some styles it can be too clean.

 

He should have said nose burning sensation. Many of us have experienced that.

 

Since you stated: “I tasted the sample and there was no sign of diacetyl.”, it appears that you do not need to conduct a diacetyl rest. I would let the fermentation continue a few more days and then transfer to a secondary for lagering.

My last lager (a Tmavy Lezak; OG of 1.054) took 7 days to finish but I let it sit a few more days before transferring to the secondary.

Please report back how your lager turned out.

Cheers!

 

Diacetyl may still be forming. It's not a direct byproduct of fermentation, so the fact that he doesn't taste any now doesn't mean that its precursor isn't present.

OP: I would do the rest anyway, which would both accelerate the formation and the subsequent reduction. It's cheap insurance. Your beer. Your choice.

 

Regarding diacetyl, can you elaborate on "it's not a direct byproduct of fermentation"? I believe I've had a misunderstanding there. Thanks.

 

Sure. A byproduct (more accurately, an intermediate compound produced in excess) of yeast synthesizing some amino acids is alpha-acetolactate, which the yeast dump when they no longer need it. In the wort/beer, this excess alpha-acetolactate is oxidized (sometimes slowly, and regardless of the continued presence or absence of yeast) to diacetyl. These oxidation reactions happen faster at higher temps. But as long as healthy yeast are present, they can reabsorb the diacetyl and convert it to less obnoxious compounds (also faster at higher temps).

The reason I pointed out that diacetyl isn't a direct byproduct of fermentation (i.e. the yeast don't make it directly as part of fermentation) is that just because attenuation is finished and you don't taste diacetyl, that doesn't necessarily mean you're in the clear.

 

OP, it is your choice whether you think there is a need to conduct a diacetyl rest for your beer. I have homebrewed over 70 batches of lagers and I have never conducted a diacetyl rest. None of my lagers had excess levels of diacetyl. And yes, I do have a sensitive palate and can readily perceive excess diacetyl if it is present.

It may be appropriate to state one of my old sayings: homebrew the beers you like and brew them the way you like.

Cheers!

 

Great explanation, thank you. This makes sense for a situation I encountered a while back. I've made 3-4 lagers in my day, never had any diacetyl issues, but I did once with an ale yeast, can't remember the strain. In any case, diacetyl was not present after fermentation or at bottling, but my first sample bottle after two weeks of conditioning had a small trace of it. Thankfully my next sample a week later, and each bottle after that, had absolutely no traces at all. I imagined that the diacetyl was able to be cleaned up because the yeast was given more food and the bottles were stored at conditioning temps.

Few more questions, hopefully the OP doesn't mind since it could be beneficial to his/her situation:
1) In the OPs scenario, is it more likely that diacetyl has already came and went? Yet to appear, but will? Or unlikely to appear at all?
2) Speaking of "Yeast don't follow your schedule," if diacetyl was present, would you suggest leaving at d-rest temps until the diacetyl disappeared, as opposed to 2-3 days? Is there a temperature threshold in which it is too cold for yeast to clean up the diacetyl?
3) If it is possible to suppress diacetyl from forming, what would you do to give you the best chance?

 

Having never used WLP940, I'd hate to guess. It' supposed to be a "clean" strain, FWIW. But to me, a rest is a no brainer with any lager because it's cheap insurance.

I'd recommend 2-3 days at 65F-68F and then taste to make sure. If it's an important batch, It wouldn't hurt to have more than one person taste it, given varied individual thresholds. I've seen more than one disappointed, frustrated face at homebrew club meetings after people not particularly sensitive to diacetyl shared their work with others, i.e. either club members or competition judges.

Yeast can reduce diacetyl at lower temps, but more slowly. I don't know the practical lower limits.

Just be JackHorzempa. He has homebrewed over 70 batches of lagers and he has never conducted a diacetyl rest. None of his lagers had excess levels of diacetyl. And yes, he does have a sensitive palate and can readily perceive excess diacetyl if it is present.

But seriously, to prevent diacetyl from forming, you'd have to either prevent the yeast from producing and dumping alpha-acetolactate into the wort/beer, or you would have to eliminate oxygen in the wort and finished beer. I don't know if the former is possible. The latter is not.

 

I will teach you to be me. That way you will be both good looking and smart!

To the topic of “it is possible to suppress diacetyl from forming”, diacetyl is produced in every beer fermentation with the amount peaking during the exponential phase of fermentation. The yeast then reduces the diacetyl during the stationary phase of fermentation; this process is referred to as diacetyl reduction.

The issue whether you need to conduct a step called a diacetyl rest is very much related to the stationary phase/diacetyl reduction. In other words, is it necessary to take an active step called a diacetyl rest (i.e., raise the temperature of a lager during the end of the primary to warm temperatures like high 60’s)? Some homebrewers do conduct a diacetyl rest and it can indeed be viewed as cheap insurance. For all of the lager beers that I have brewed, the yeast properly reduced the diacetyl during the stationary phase of fermentation with no need to elevate temperatures.

Some folks will state that some lager strains need diacetyl rests while other lager strains do not. I have homebrewed with the following lager strains: WY2206, WY2035, WY2272, WY2042, WY2124, WY2278, WY2633, WY2001, WLP830,WLP802, … and I have never needed to conduct a diacetyl rest for any of those yeast strains. Needless to say but YMMV.

Here is a good article on Diacetyl: Formation, Reduction, and Control:http://morebeer.com/brewingtechniques/library/backissues/issue1.2/fix.html

You will take note that in Table I the amount of diacetyl for the W34/70 yeast is already at 0.09 mg/L by day 9 which is below the flavor threshold for diacetyl of 0.10 mg/L. You will also read in the article: “Some additional reduction occurs in cold storage, but at a very slow rate.” So, the diacetyl level will continue to decrease during lagering (I personally lager for 6-7 weeks).

It has been a very long time since I read this article; I ‘rediscovered’ where I learned that a significant number of beer drinkers are insensitive to diacetyl: “Even today it is estimated that 20% of beer drinkers do not detect the presence of diacetyl even at rather high concentrations.” Unfortunately I am not part of that 20%; I am very sensitive to diacetyl and I despise the presence of high level of diacetyl even in those beer styles where it is claimed that diacetyl is OK (e.g., Stouts, British Pale Ales, etc.).

Cheers!

 

Not untrue. But potentially misleading. Diacetyl can continue to be formed (through the slow oxidation of its precursor) at the same time that already formed diacetyl is being reabsorbed and reduced by the yeast. i.e. it's not a discretely stepped process as sometimes implied in magazine articles.

 

One aspect that I meant to discuss in a prior post but neglected to do so is that it is OK to have diacetyl in beer; it just needs to be below 0.1 mg/L (the flavor threshold) for me.

Some folks might like a little bit of diacetyl (i.e., more than 0.1 mg/L) in their beers. For example, Pilsner Urquell has a small (but perceptible) amount of diacetyl in that beer which I personally do not find objectionable since it is a low level flavor. When beers have diacetyl levels of Redhook ESB of circa 2002, then that is a horse of another color.

Cheers!

 

Diacetyl...a brewer's and taster's curse, but can be fleeting as a puppy's fart... and an enigma