Acetaldehyde in three consecutive batches?

[PasbitinusBluinusRibbinus]

Okay, this one is driving me nuts.

I've been brewing for a few years and have dumped maybe two batches. Yet, the last three of my brews have had serious acetaldehyde problems. It doesn't make any sense to me; my process hasn't changed and has always seemed sound.

This last beer was a IIPA that sat in primary for 3 weeks, another 5 days dry hopping, and then got a lengthy (1-2 week) cold crash. Kegged and was immediately hit with green apple.

Oxidation seems unlikely, pitched 2 packets of yeast. Should have had more than enough time to clean itself up - it's crystal clear.

Any suggestions? Could it be time to throw the buckets out?

 

[mbobhat]

I would say leak in your fermenter. Or sanitation somewhere.

I got the green apple only when my fermenter has a slight air leak, and I let it sit in there for a month or more. It seems strange for you to get it after only three weeks. What yeast are you using?

 

[Beernik]

These are the places that I think you could get acetaldehyde:

1. Primary infection somewhere in your process: fermenter, sampling, etc.
2. Underpitch
3. Pitching too hot
4. Fermenting too hot
5. Oxygenation during fermentation: loose lid, suck back
6. Secondary infection: kegs, keg lines, etc.
7. Oxygenation after fermentation

It would likely show up in all your beers pre-kegging for the first five. If it shows up after kegging, it's probably one of the the last two.