I've got the brewing version of a hitch in my swing. With one exception, every time I have ventured into a lighter beer, I have run into moderately strong acetaldehyde/fruity off flavors. I did manage to brew a Wit last year without them, but now I am wondering if the flavor was masked/integrated into the Wit. I thought I had my problem diagnosed, but now am forced back to the drawing board.
Last year, I brewed a Cream Ale w/ S-05 and this year a Blonde, also with S-05. I fermented both cool (low 60s). While the Blonde is not as sever as the Cream Ale was, both have the same off flavor. I was blaming my problem on a combination of the S-05 and perhaps too cool of a fermentation, causing the yeast to flocculate before their job was done. However, I just transferred a CAP fermented with San Fran Lager yeast (WLP810) at 57 degrees to secondary after two weeks and change in primary. I picked up the same problem. Yes, it's early for this beer yet, and I'm hoping some conditioning helps, but by now, I know the problem when I see it. I'm going to try to clean it up by doing a warmer (64) rest before bringing it down to the mid 50s for conditioning. However, I would really like to nail down the cause of the problem in the first place. The recent issue with the CAP has eliminated yeast as an option. That leaves me with just two possibilities: pitch rate and water.
Being in Illinois, I have hard-ish water. Anything lighter than an Amber, it's too hard. So, when I have gone lighter, I get water from one of those drinking water vending machines at the grocery store. I didn't think the water could cause this problem, but as it's the only common thread between the beers, I'm now wondering if it's part of the problem.
I'm also wondering if my pitch rate and aeration is causing the problem. I've always thought my aeration was o.k. When I transfer from my boiler, I run the wort through a spray aerator, a strainer, and a funnel into the carboy. This usually produces enough foam that it's coming out of the carboy. I do concede that under-pitch could be a problem. I would think a rehydrated pack of S-05 would be adequate. The CAP did have a problem, though. I had a failure to start from a harvested yeast, so I straight pitched another vial. While fresh, this is probably not the best.
O.k., that's the long run-down. Any insight as to the cause of my problem would be appreciated. I would hate to be banned from entire categories of styles! Thanks in advance!