Dos Equis = Diacetyl?

A few months ago, I made a batch of Dos Equis Amber clone. It got a bad diacetyl infection in the keg. I cleaned it up pretty good with a US-05 starter in the keg.

Tonight, we had dinner out. I ordered a Dos Equis Amber draft. Guess what I smelled? Yep, butter. I think they had a slight diacetyl issue in their keg.

Is there something special about Dos Equis Amber that leads to diacetyl issues?

I have never tasted diacetyl in the Amber but, I have tasted it in the Regular. Actually Every time I have it on tap I taste diacetyl in it.

I've noticed it in Killian's Red...

I also have noticed a lot of tapped Killain's in bars, just on the verge of having an acetobactor infection, and just starting to taste like vinegar.

Diacetyl isn't an infection, but a byproduct of the fermenting process. It ends up in beer when the yeast don't get around to, or are prevented from, cleaning up after themselves.

I don't know about Dos Equis, but in some beers, such as Pilsner Urquell, it's part of the profile to add fullness and mouthfeel. Sometimes it'll come through in the flavor - Seems to happen sometimes if the beer sits and gets a little warm.

Diacetyl is produced either by yeast, or by anerobic bacteria.

The Diacetyl produced by yeast is usually consumed by the yeast later in the fermentation cycle. When making a lager, a "diacetyl rest" is sometimes required to allow the yeast to "speed up" and consume the diacetyl.

The Diacetyl produced by a bacterial infection you are stuck with, unless you add more yeast to consume it.