Just brewed a cream ale and after two weeks I pulled a sample, no hydrometer sample because I broke it and haven’t replaced it yet, and it smelt like green apples. The first sample was super yeasty and smelt the most of apple. The second and third samples were clear and had only a faint smell of apple. One didn’t even have an apple taste. The recipe is basic: 80% two row, 20% flaked corn with a 30 min hop addition of 1 oz cascade. I pitched wlp001 without a starter due to the low SG. I didn’t even bother doing a calculation. Yeast wasn’t too old so felt it would be fine. Fermented it at 63 then after 3 days ramped it up to 69, two degrees each day. I ferment in a speidel and I put the temp probe on the outside of the fermenter and cover it with tape and bubble wrap, hoping to read the fermenter and not the outside temp. I use a heat wrap to control the temp. After two weeks the beer should be done fermenting and the samples are pretty darn clear. From my understand is the Apple smell and taste is Acetaldehyde. The recommendation is to let it sit longer to allow the yeast clean up and it should be fine. I usually keg my cream ales in like 10 to 14 days after pitching. I’ve never gotten green apple before any beers. Due to the length already I don’t think there is enough active yeast to clean up. Any thoughts on the cause? Do I simply just need to let it condition longer?
Sounds like classic acetaldehyde. Yes, the yeast should clean up after itself unless the yeast was unhealthy or it is a high gravity beer. If you reached FG and everything else is right then the yeast will probably pull through. Be patient, it can take a few days for the yeast to do the remaining work. You might want to raise the temp a little bit if you can. Gently rousing the yeast could help too, so long as you don't add Oxygen. Cheers Cheers
Krausen it. Will naturally carbonate your beer resulting in a “creamier” cream ale and clean up the Acetaldehyde.
I am not familiar with that process. The beer is done fermenting and I have nothing brewing and I don’t have time to brew anything for a week or two. I planned this cream ale as a starter for my next beer. Plus, I like cream ales of course.
My guess is there's probably enough yeast to reduce the acetaldehyde. I'd let it sit until it's undetectable. You could krausen it, like @wasatchback said, but my guess is you won't need to. As for the cause, well you underpitched a bit, so I'm not too surprised. Every beer has some acetaldehyde (temporarily), and the yeast usually cleans it up (eventually).
I think if you reached FG there is more than enough yeast in that wort. The yeast may have been stressed before during and after fermentation, and if you under pitched was likely working OT in the lag phase and during the primary. But with a flaw like this, which is not really all that big a headache, just wait it out. The yeast could be cranky. They might not be putting in their best effort. And they definitely are not building a resume. But they are not on strike. They will get up and go to work. So they own it, let them do the work. Maybe 72F, 75F as an incentive, if this drags on. Cheers.
On a side note since my hydrometer broke I didn’t measure the SG. This is the first time I used a sous vide to maintain my mash temp as opposed to just putting it in the the cooler. During the mash I stirred it every 15 minutes. I wonder if that bumped up my SG and combine that with no stater I under pitched.
I hate it when my yeast are cranky. Acetaldehyde is always produced during fermentation . . . it's the step before ethanol is created. During the conditioning phase if given enough time and enough healthy yeast it will be broken down. It's pretty easy to give it time and if the little buggers aren't too cranky it should clear up. This may be more than you are interested in, but here's a pretty good description of how it all works: https://www.khanacademy.org/science...respiration/v/alcohol-or-ethanol-fermentation Consider yourself lucky, the "green apple" flaw is not that common . . . I've never encountered it. This makes you an experienced acetaldehyde taster. But before you pat yourself on the back, ask an elf for a hydrometer. EDIT: Are you over 2 weeks and still getting the green apple? If so, the yeast might be crankier than what's needed to clean up. As recommended I'd raise the temp and maybe a good rouse . . . you don't want them to go dormant.
In my bottling days, I 2-3 times had some acetaldehyde issues that cleaned up as bottles primed. More recently, as a kegger, I've sometimes had some diacetyl issues, which I solved by bringing the keg to temp and adding some active yeast (usually yeast pulled from a starter made with US-05). This has helped every time. I bet a similar action would help here.
