Seems to be some discussion on diacetyl recently so I thought I'd update.
I am still battling the honey problem... convinced its related to diacetyl as suggested but to my tastebuds its a distinct honey(ish) smell which is brought out in the taste of the beer. I struggle to see it as "popcorn" or "butterscotch" but then I've always hated honey, period, so maybe I'm supersensitive to it, needless to say my no 1 objective is to get rid of this taste.
As Trev suggests it may be Pentadione, the best chemical explanation I've found on this is here:
http://www.draymans.com/articles/arts/03.html
An excerpt: "Pentanedione on its own has a sweet honey-perfume smell and diacetyl resembles butter or butterscotch. Of the two, diacetyl is more significant because it has a taste threshold 10 times lower than its partner does, and most yeast strains make more diacetyl than pentanedione. If the pentanedione fraction overpowers the diacetyl fraction I strongly suspect bacterial contamination. Pentanedione is very similar to diacetyl but only one-tenth as much is found in beer. For most people the flavour threshold for diacetyl is about 0.15mg/L and 0.90mg/L for pentandione.. Diacetyl is formed only when there is oxygen in the beer. It also means that it is, to some extent, inevitable, since the wort is usually strongly aerated at pitching."
So maybe that means I have a persistent bacterial infection but as said I think my sanitation technique both for fermenter and keg and lines is pretty good.
I since tried a lager which fermented at 10 deg C and raised the temp on completion to 20 deg c for 24 hours. I had it cc'ing for 4 weeks at 2 deg C but again had the distinct honey smell and taste. I was ready to spit the dummy and toss the toys out of the pram and bin it, but controlled the urge and removed it from the kegerator and left it at room temperature for 2 days (stinking hot 27 deg C...). I then cooled it back down fully expecting to have had the beer spoiled but noticed that while the honey smell and taste was still there it had reduced significantly.
That probably means my diacetyl rest was not long enoughso my current batch I am going to leave for 3 days at 20 deg C and see if this has any impact.
Or maybe there is merit in leaving the brew after racking to keg at room temperature for a few days before dropping it down to kegerator temps ?
