Off-flavours and aromas AFTER kegging

[Buccaneer]

While I seem to have rid myself of acetaldehyde, for the last 3 batches I've made I've managed to pick up isoamyl acetate (banana) aromas and some sort of weird vegetal flavour. However, I only notice these things AFTER the beer has been sitting in a keg for a couple of weeks. ie, I don't notice these things at the time I keg.

In most previous batches, I tended to get a lot of acetaldehyde. I would notice it at kegging time and for a couple of months after. It would eventually almost completely subside.

While working on trying to solve the acetaldehyde problem, I've made 3 changes.

1) I started adding servomyces right near the end of the boil. It seems to have done the trick.

2) I switched from a 5/16" racking cane to a 1/2" auto siphon.

3) I stopped adding 1/2 sugar to the keg at transfer time.

I only started adding sugar when, one time, I noticed that the beer I had bottled and let condition had less acetaldehyde. I started adding some to the keg to see if that would help. It did a little bit, but not really significantly, so eventually I stopped. I added the sugar for maybe 6 batches and haven't for about a year.

The acetaldehyde went away when I started using the servomyces. And that's when the other stuff started showing up.

I don't think I've changed anything else. I'm still careful about my sanitization. I use rolling boils and I chill quickly.

I'm at a loss as to what's happening. Any thoughts? I'm wondering if the bigger siphon is moving the beer around more in the keg and it's picking up oxygen.

[jason.loxton]

I can't think of any reason why you should be picking up those flavours if you've got the beer chilled. If it were bottles, I'd say you've got an infection. None of the hypotheses you offer seem plausible to me. You should not be introducing oxygen through a properly functioning autosiphon, and even if you did the flavours you describe aren't oxidation flavours, but sound more like fermentation flavours or hop related flavours.

My best guess is that It might be that the flavours were always there, but that the only come to the fore as the beer conditions in the keg and other flavours become muted.

As a start, I'd assume that they start earlier in your process (assuming that you'r kegs and transfer equipment are clean) and check your yeast pitch rates, sanitation, and hop freshness/contact time/etc.

That's all I've got.

[oceanic_brew]

I second the above. Any off flavors I get are due to fermentation/infection/recipe issues and are noticeable in the keg sometimes and have gone undetected previously.

I got acetyldehyde from a DIPA I did recently, 1.080 OG. I pitched a large starter of 1968 London ESB that didn't take off so I repitched another large starter and within a few hrs I started to notice activity. The first starter I found after had frozen and thawed, there was probably some viable cells leaving a huge lag time that I'm assuming developed a load of off flavors due to the massive cell growth.

Another beer I pitched a 1.050 beer on a yeast cake from a 1.080 batch, huge acetyldehyde.
I tried krausening both and the acetyldehyde cleared up with that a bit of aging.

It was good to have a little personal experience with yeast issues.

[oceanic_brew]

Could you post a recipe?

I got some nasty vegetive flavors recently from a DIPA that I did with Belgian Ardennes yeast. I bought the yeast for a Brewdog exchange I did with some guys at Nobel Grape and the first generation was delicious but subsequent batches kept throwing phenols that did not match well with the American citrus hops. It was bordering a rotten vegetable flavor/aroma by the third use and then I tossed it.

Also had weheinstephaner 3068 yeast that began throwing a weird metallic flavor in batch after batch. Tossed it and bought fresh and problem seemingly solved.

[Celiacbrew]

http://beersmith.com/blog/2012/04/10/di ... ewed-beer/" onclick="window.open(this.href);return false;

Could it be DMS from an infection?

[oceanic_brew]

http://beersmith.com/blog/2012/04/10/di ... ewed-beer/

Could it be DMS from an infection?

http://beersmith.com/blog/2012/03/07/es ... r-brewing/

This article that's referenced in the one you posted has some great information on ester formation. The banana that the OP notes could be from inadequate pitch rate.

[McGruff]

I was getting off flavours around 10 - 14 days after kegging. Not an in your face infection, but something was off. I went back to my process and found out when I added gelatin I didn't boil my 250 ml of RO water I used to make the gelatin. I didn't think I had to since I sanitized the 19 L bottle at the water store. I got the water from my water cooler though. This was doing it. Now I boil the water for 10 minutes, cool it down to 150 F and make my gelatin. No more off flavours anymore. I do clean the water cooler every 3 months or so. God, beer is so unforgiving sometimes.

[Buccaneer]

Haven't been here in a while.

I'll just reiterate that the weird flavours go away. Eventually. I brewed a helles and marzen in December and it really took until mid-March for the weird stuff to go away.

I've been reading lots of stuff since December to try to figure out what's going on. Everything was suggesting pitch rate. I brewed a porter 4 weeks ago and, as an experiment, I used two yeast packets instead of one. I left it in the fermenter for about 10 days, then bottled. Cracked one on about day 24 (since brewing) and apart from the beer still being a bit 'new', there were no off-flavours at all.

I brewed a lager on the weekend and doubled up on the yeast (34/70). I'll keep you apprised about how things go.