Would be happy to have some help from more experienced brewers here! I have very little experience with infection beyond an unwanted Brett appearance or two.
Tried my hand at a berliner weisse for the first time a few weeks back; ran into some troubles which @Agate helped me with
here. It seems some unwanted yeast or bacteria crawled in each of my batches during the lacto stage, which I did around 75-80 for a few days. Saved one of the 5-gallon pails (whatever chewed up my wort wasn't too bad), but the other was terrible -- not sure exactly how I'd describe the smell, maybe something like mothballs -- and I dumped that one.
Fast forward to last week, and I'm trying my hand again: already bought the fruit puree and the grain bill is cheap. That same fermenter was my last one left, and it was soaking alternately in diluted bleach and star san solution with frequent rinsing and some time in the sun since the last infection. Assuming the problem last time was the long, room-temperature lacto stage, I kettle-soured in 24 hours around 115-20. Great pH drop in short order with the same lacto B culture as last time (I save cultures from the starter), and I racked the now-sour wort into that fermenter and immediately pitched a small starter each of brett B and L. At time of racking, I didn't notice anything unusual and I didn't see any gravity drop over the 24 hours in the kettle.
Hit krausen earlier this week, nothing unusual about it, and it had died down by last night. Eager to see how this second batch was coming along, I took a sample and was disappointed to find the same gross aroma as last time. The best I can continue to come up with is something akin to mothballs, but in my search to figure out what is going on I guess I'd call it fecal or like vomit (really just because those are the most disgusting descriptors I can find). Based on that, the best I can come up with is mercaptan or one of indole-producing bacteria or butyric acid discussed at the
Sour Beer Blog.
I don't know where mercaptan would come from, since this had a very low OG and I pitched two starters of brett. Given that I turned this up to 120 at times that should rule out butyric acid-producing bacteria. Leaving only indole-producing bacteria. I'll note, however, that this seems to be getting worse (I took a whiff again today), and per the Sour Beer Blog my low pH should knock out anything actively producing these notes.
I'd like to get to the bottom of this, either figuring out that there's something wrong with that pail that I can't beat, or that my BW process is faulty. And, to figure out if I can salvage this! I'm both frustrated and bummed out at this point, as I thought I'd made up for my errors last time.
Sorry for potato quality, but here's a recent picture. Could well be the remnants of the krausen, as it only recently fell, but figured it was worth a shot: