I'm looking for a sanity check. I've been brewing for many years and can count the batches I've lost on one hand. However, my last two batches were terrible - Acetaldehyde (green apple) bombs and I cannot figure out what the hell is going on.
Couple suggestions I've read are to leave it in the primary longer. Pitch more yeast. And ferment at cooler temps.
But reviewing my brewing techniques, I'm not sure any of those are the root of the problem. I let this last batch primary for 21 days (an APA) and used WLP001. I did use a yeast starter and I control my fermentation temps (67-68F).
The only thing I've changed is how I prepare my yeast starter. I used to make the starter 48hrs. before brew day. Meaning, if I brew on Sat. I prepare the starter on Thur. night. And I leave it on the stir plate the entire time. I recently was listening to the Brewing Network and someone suggested making the starter the night before (ex. Fri. night) as you will be pitching it at high krausen. So for the last two batches I made the starter on Fri. night. Could this be the issue? I'm not sure why but that is the only thing I've changed.
The only other thing I can think of is an infection. I'm going to replace all my post-boil hoses and stick the air stone in boiling water for 20 min (I don't own a pressure cooker yet).
Any help very appreciated.