I have brewed a lot of pale ales. Usually ferment with US05 and historically ferments have been circa 72 - i'm working on lowering that to the 60s. Recipes include mostly 2 row, a bit of munich, and half pound to a pound of crystal 40. I also have added some wheat malt and carapils to try and increase mouthfeel. I'm tasting a bit of butter/caramel/not sure which. It isn't unpleasant and it varies (probably my palate, not the beer). I serve it at about 38F and carb'd to 2.5 volumes. The finish of most of these pale ales has the taste I'm talking about and i can't determine if it's the dextrine/unfermented malts or diacetyl. Any hints???
Caramel flavors can also come across as toffee or butterscotch which could be thought to taste like diacetyl.
JZ had some interesting stuff to say on kettle carmalization during his "Scottish Shilling" podcast/show on the BN and how he stopped using that process because it produced flavors that judges equated with diacetyl in his Shillings.
Does the flavor become more or less pronounced when you let the beer warm up in the glass? Is it more pronounced in the beer you make with 1 lb C40 over the 1/2 lb C40 beer?
Crystal 40 has a good bit of sugar sweetness and is just starting to trend into the caramel sweet without fruit to my pallet. I usually sub C60 for C40 because I like that little hint of caramel sweet better than just "sweet."
the recipe for the beer i'm currently pondering has 0.5 lb wheat, 0.5 lb 40, and 0.5 lb carapils per 5 gallons. It does seem to be more pronounced when it warms up - especially the dregs in the glass the next morning.