Toffee is made with butter and sugar. Most are familiar with toffee as it tastes like caramel and butterscotch.
Winning Homebrew states that Diacetyl equals butterscotch.
So it appears that Diacetyl is a butterscotch/toffee like flavor.
And per the BJCP, this is acceptable in an Irish Red. Very light buttery aroma is optional (acceptable). It never states this flavor or aroma is a defect or flaw.
Diacetyl reminds me most of buttered popcorn, which makes sense because the fake butter on popcorn IS diacetyl. It doesn’t really remind me of butterscotch or toffee as much. I believe I pick up those flavors (when present) more from malt than from diacetyl.
Some say at very low levels, even though you might not be able to taste it, diacetyl might feel oily on your tongue, a “slickness”.
Diacetyl in Home Brewed Beer – The Butterscotch Flavor
by Brad Smith on April 21, 2012
Diacetyl is the butterscotch or buttery flavor in your home brewed beer.
Summary
Diacetyl (butterscotch flavor) and pentainedione (honey flavor) are a natural biproduct of fermentation, but both can be broken down by healthy yeast when fermentation completes.
The primary method for controlling diacetyl (and pentainedione) is to pitch the appropriate quantity of healthy yeast from a yeast starter and ensure that the yeast remains healthy.
A diacetyl rest for lagers (raising it a few degrees during fermentation) can also help reduce diacetyl in the finished beer by helping the yeast break down VDKs.
Commonly described as having an artificial butter flavor (think movie theatre popcorn) that leaves your mouth feeling like an oil slick, diacetyl is actually produced in varying amounts by all yeast strains in all kinds of fermentations.
I’m so confused.
I can’t say I’ve ever tasted it once. Maybe I’m immune to its charms?
Some people don’t notice it. 20 years ago I thought it was a pleasant feature of craft beers. I still don’t mind it but it isn’t as common as it once was, except in some (not all) British-style ales, including those on the east coast of the USA, as well as in Pilsner Urquell.
Like Denny said, I work backwards from a mouthfeel to a taste. Those who are sensitive to the flavor pick it up directly and some are overwhelmed by a relatively low level. I like it in many British Ales, but not in lagers.
The Czech lager and English Ales allowing for diacetyl don’t have to approach the level reflected here in the spiked beers (600 ppb) to be considered flawed by a discerning BJCP judge. Indeed, if it is too pronounced, it won’t be pleasant for those sensitive to diacetyl. Like others said, pitching a good volume of healthy yeast usually prevents its formation in high enough concentrations to linger into the finished beer.
Of all of the Czech beer that I have consumed, diacetyl was never noticed. Is it allowed…well I guess so. Is it actually there, at a level that you can taste?
