Last year I chased this off flavor around in my alts and kolsch. It was so common in my beers that it became "Rich Character" (RC) as dubbed by my competition team. This year using different equipment it disappeared. That in itself is anecdotal since I've changed so many things.
Then, last week at my competition team meeting one of my friends on the team brought a schwartzbier that had the RC in it. It was unmistakable. That got me to thinking again where it was coming from. I certainly don't want my friend to beat his head against the wall like I did. He's been making lagers as a starter beer for a big baltic porter. The porter is phenomenal and one of the local breweries wants to brew it. So my friend is making sure that he can reproduce it.
What I'm thinking is that this isn't a contamination issue. I'm really careful and the RC didn't show up in hefe's or saison, just alts and kolsch. I think it's a fermentation byproduct associated with most likely temperature. I think I've smelled the RC in starters with 1007 before that were done at room temp, but I can't be certain.
So, I'm going to conduct a test and make two starters from the same wort. I'm going to put both on stir plates, but one will be in my fermentation chamber, the other in the kitchen at room temp (74*).
If I get the RC in both starters I'll know that either temperature isn't a factor OR that my ferm champ temp control isn't as good as I thought. I'll have to repeat the experiment to be sure. I'm also assuming that it's in the starter and carrying over to the beer.
Other sources - over pitching, under pitching, contamination, too high concentration of starsan?, PBW or soap residue, water chemistry, O2 levels at pitching
In the meantime, I'd like to hear from anyone here that makes Alts, Kolsch, and Lagers to see if you all get any of the RC in your starters.
My starter procedure...
I use yeastcalculator.com to figure out how much DME I need. Usually it's about 7ish grams in 2L of water getting the OG to 1.037. I use my tap water for starters. Usually untreated (by me). I boil in a pot and cool down with an IC, then put it in the fridge until it gets to about 70 deg. Dump into a sanitized Erlenmeyer flask and add the yeast and put it on the stir plate for 12-24 hours. I usually pitch right into the wort rather than decanting the starter.
Cheers.