Issue:
Hi guys, I’m struggling with an off-flavor in some of my lagers. I think the off flavor is acetylaldehyde (a former Ninkasi winner/now professional brewer told me so with one of my beers).
I’ve tasted this off flavor in my beers brewed with Wy2112 (san francisco lager), Wy2001 (urquell strain) and Wlp833 (bock), whereas my lagers with similar grain bills, identical temp schedules, and identical water profiles, using Wy2124 have been perfect.
Process (All-grain, BIAB, 5.5 gallon batches):
I pitch my yeast according to BeerSmith’s calculator using a stir-plate on my starters for the first 36 hours, after which I refrigerate for 4-5 days and decant the starter beer. I use wyeast yeast nutrient as directed in the boil and oxygenate with pure O2 through a 2 micron diffuser stone for between 45 and 120 seconds depending on the OG.
My mash temps are always between 150 and 155F depending on the beer, I always boil for at least 60 minutes, and during the winter am able to chill to 68F in 20 minutes or less. After which, the wort is left to chill in the keezer (air-locked, in sanitized fermentor) until it reaches my desired pitching temperature.
My fermentation schedule for the above mentioned yeast, excluding the steam beer, is to pitch at 50F and let slowly rise to 54F over 7 days, then let free rise to ambient (62-64F) for a week, followed by several days at 68F.
I gently siphon to CO2 purged kegs, purging the headspace numerous times, and let ‘lager’ while they carbonate and clear (usually about a week).
My water is from my own well, which was tested by Ward Labs last fall:
I add 1tsp of Calcium Chloride to each batch.
Sanitation:
I clean with PBW/scent free OxyClean, and sanitize with StarSan. Ball locks and posts are sprayed with 70% ethanol prior to attachment. Beer lines and taps are cleaned periodically with PBW and a caustic line cleaner.
Comment:
The steam beer had a god awful sulfury apple aroma and flavor and I couldn’t drink it. I let it sit for a month and it was still terrible. My Vienna lager and Urquell pils both have much more subdued green apple flavors, and no aroma, but it still bothers me. In between these three beers I’ve produced numerous ‘perfect’ (to my palate) german pils, and other sundry light lagers. No issues with my stouts, pale ales, or saisons, either (all using the same water profile). I brewed a light mexican lager with Wlp833 that was great, and then I used 833 on the Vienna, that was not great…what the hell?
From what I’ve read, yeast stress and/or oxidation is often responsible for acetylaldehyde. I believe that I am pampering my yeast, and I believe I’m avoiding copious amounts of O2 ingress. Any ideas would be greatly appreciated, I’m getting really frustrated and I particularly hate this apple off-flavor. I take this hobby seriously and want to get to the bottom of this.