I have had a recurring off-flavor in my ales that I would like help identifying and preventing.
The flavor is a yeasty flavor with some savory components. I have tasted it a few times in commercial beers, but usually it's less pronounced and fairly tolerable. In my homebrews, it can be overwhelming and I've even tossed a few batches because of it. Prior to fermentation (post sparge), the flavor is not there. It only appears after fermentation has started. It always accompanies an overproduction of trub, with more "floaters" than normal and more haze than normal. I can usually smell it right away, often times right after fermentation starts. It usually does not subside with bulk aging, but a few times it seems like the brew has become more tolerable after being kegged for a month or two.
It does not really match any of the typical off-flavors, but does almost have a blood-like component and sometimes a sulphur component. However, a metallic flavor ostensibly comes from metal equipment, not the fermentation, and sulfur from lagers...
I have never had this problem with sour beers, ciders or lagers, only ales, and I think always with S05, one packet for a typical SG of 1.050 - 1.060, most often rehydrated, sometimes directly pitched. I thought I had used a different yeast in the last one, but after looking at my notes, it was in fact, S05. I did buy a 6-pack of S05 a while back, so maybe the yeast was bad, but it seems like I have had this problem before I bought that pack, but maybe not as often.
Per jsolarski's comment, I did solicit some taste notes. Unfortunately, all I really got was a quick head turn, clearly noting the off flavor, but not really any good descriptions, except perhaps a bit salty. I don't pick up any salt flavors, but perhaps this comes from the savory notes.
I'll bring a growler to an event tonight with some other homebrewers and see what other tasting notes I can get.
Possibly related, What exactly is yeast-bite?
UPDATE: I had a few friends try the beer and one home brewer in particular identified it right away as Tetrahydropalmatine (THP), and he described the flavor as mousy or cheerios. I think this sounds plausible since I've described it as savory, and another as salty. According to milk the funk,
"mousy", "urine" (in high amounts) Cheerios® or Cap'n Crunch® (in low amounts), "breakfast cereal", or more generically, "cracker biscuit" flavor
Unfortunately, most of the article is with respect to sour beers, and I do not have this problem with sour beers. Also, much of the production is mentioned post-fermentation, but in my case, it is noticeable at the very start of fermentation.
There's a lot of speculation in the article, but not much that matches my experience.
This article mentions
In the presence of oxygen, Brettanomyces will produce both ETHP and ATHP from lysine and glucose or sucrose, though the exact metabolic pathway remains unknown
I'm not using brett, but perhaps S05 can do this as well?
So, given that, how do I go about preventing it?