My friend and I got a little too ambitious and brewed an imperial stout with cocao nibs and coffee in the secondary. The fermentation got too hot and it's a little fusel-y. The coffee is overpowering and has added a bitter, stale taste. It's drinkable but kind of a mess. Took close to 2 months to reach a normal level of carbonation. Anyways, I am wondering what could have caused a thin layer of foam in the bottle. I don't think it's due to incomplete fermentation as the FG was consistent for weeks before we bottled it. There was a thin layer of foam in the secondary as well but it didn't show any of the obvious signs of infection. I assume it must be infected in some way, but it doesn't taste it. Maybe I am not sure what I am looking for, or the coffee/booze flavor is overpowering any other off flavors?
Holding up a powerful flashlight behind the bottle. Maybe it could be some sort of sediment due to the coffee/nibs rather than foam, I just figured it would have settled out by now... Putting it in the fridge doesn't seem to have an effect either.
That thin white line just below the bright light? Hard to tell from the pic. What does it look like from above? Like fine bubbles? Smooth? Rough? Stringy? Nibs have a buttload of fat in them. It could be that.
