Diacetyl rest too early

Hi all
I am busy fermenting an Oktoberfest with WLP820 yeast. I have read all kinds of things about issues with this yeast, so I kept that in mind when brewing this batch. I made a large starter, and fermentation went along fine at 12degC/54degF. OG was 1.055, with estimated FG 1.015. I started a diacetyl rest at 1.027. I thought it was a bit early but I figured that my fermentation chamber would take a while to get up to my d-rest temperature of 18degC/64degF, so in effect the d-rest would only really start a day later at around 1.024 (with this yeast I really did not want to get stuck at a FG higher than expected and having missed the chance to do a d-rest). The gravity is now down to 1.014 and the yeast is still active, but the beer has a definite banana aroma. I am wondering if I should have left the d-rest for a bit later, or if my temperature was wrong. Is it maybe better to miss the window for a d-rest than to start too early? Can I get rid of the banana somehow?

I haven't used that specific yeast, but often raise my lagers for a d-rest at about the point you did (although I go to 16C rather than 18C). I've noticed lots of strange smells from fermenting lagers, including banana, that always disappear with aging/lagering.

You should be fine. As long as it's off-gassing the yeasty aroma it should reduce with lagering as long as your early fermentation temp stayed low enough to suppress ester formation. Munich type malts and that yeast sometimes create those aromas early on without affecting the final flavor of the beer in my experience.

The FG ended up at 1.010, much lower than expected. I can only imagine I mashed at too low a temperature. That works out to almost 40% of the fermentation at diacetyl rest temperature. It's lagering now, hopefully the banana goes away. I'll know one way or another come October!

chrisjpryor said:

The FG ended up at 1.010, much lower than expected. I can only imagine I mashed at too low a temperature. That works out to almost 40% of the fermentation at diacetyl rest temperature. It's lagering now, hopefully the banana goes away. I'll know one way or another come October!

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It's perfectly fine to raise the temp at the point you did. If it was at the initial fermentation temp for at least 3 or 4 days, you should be fine. The esters are really produced in the growth phase in the first couple days, that's when it's crucial to have the proper temp. Otherwise, raising it like you did helped a) clean up diacetyl and, b) helped it fully attenuate. It'll finish nice and dry but still be malty, like a good oktoberfest should. Sometimes commercial versions are too sweet and have too much caramel malt. I don't want to drink liters of that stuff. The banana aroma will hopefully dissipate and not come out in the flava flave.

So here's a follow up... I bottled yesterday, and this beer is like freshly baked banana bread and murkier than any beer I've brewed before. Even after lagering for a month, and fining with gelatin it looks like muddy pond water. I'll crack a bottle open in a month's time and post another update, but if I was asked to identify this beer in a taste test I would definitely not have said it was an Oktoberfest. TBH I suspect the yeast - it was said to be be WLP820 but it was from a guy who cultivates his own from existing strains.

I wonder if you got some Hefe yeast. Ales are cloudy and lagers have always been more clear, from my experience. It sounds like Hefe yeast, haha. And yes I'm pretty sure that Hefe yeast will ferment at 54F. I know I ferment mine at 62F, just 8 degrees warmer, and it gets really active even on that low end of their suggested ferm spectrum. I'd love to hear how it turns out.

I cracked open a bottle last night. It has cleared considerably with a lot of sediment at the bottom of the bottle. It tastes like a really great beer that someone decided to filter through a loaf of banana bread. Not an overwhelming flavour but it's there. It's a nice beer, just not an Oktoberfest. Still gonna drink it though!

chrisjpryor said:

TBH I suspect the yeast - it was said to be be WLP820 but it was from a guy who cultivates his own from existing strains.

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I was burned once like that by a fellow club member, very disappointing. I only take yeast from good friends now, otherwise, it just makes more sense to buy it.