[Bel Air Brewing]

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.

How about Irish Ales, as that is the subject matter here?

Does it (diacetyl) have a place in an Irish Red?

[ynotbrusum]

Fair enough:

https://byo.com/article/irish-red-ale-style-profile/

Jamil says no butter and that it can be brewed as a lager, which in my mind rules out diacetyl….

[Bel Air Brewing]

"The BJCP style guide mentions a light buttery character being acceptable..."

So I guess that's the final answer regarding an Irish Red.

[denny]

"The BJCP style guide mentions a light buttery character being acceptable..."

So I guess that's the final answer regarding an Irish Red.

The BJCP only matters for homebrew comps. It has no bearing on commercial styles.

[Megary]

"The BJCP style guide mentions a light buttery character being acceptable..."

So I guess that's the final answer regarding an Irish Red.

The BJCP only matters for homebrew comps. It has no bearing on commercial styles.

Thank you.
Can we pin this quote to our collective foreheads please?   

[Bel Air Brewing]

"The BJCP style guide mentions a light buttery character being acceptable..."

So I guess that's the final answer regarding an Irish Red.

The BJCP only matters for homebrew comps. It has no bearing on commercial styles.

I believe that was the thrust of the original question by the OP, as it pertains to home brewing and competitions.

[ynotbrusum]

Here's an article from Seibel comparing lab analysis and personal tasting on the subject:

  https://www.siebelinstitute.com/news/sensory-and-beer-styles/identifying-diacetyl-in-3-beer-styles#:~:text=The%20threshold%20of%20detection%20for,dependent%20on%20the%20beer%20style.

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.

[Village Taphouse]

Fair enough:

https://byo.com/article/irish-red-ale-style-profile/

Jamil says no butter and that it can be brewed as a lager, which in my mind rules out diacetyl….

But lager strains can definitely produce diacetyl.  Ask me how I know.     

[ynotbrusum]

Surely, but the only one (lager) permitted by BJCP to have diacetyl expression is the Czech pale lager, I believe.  I know you know!

[Bel Air Brewing]

Surely, but the only one (lager) permitted by BJCP to have diacetyl expression is the Czech pale lager, I believe.  I know you know!

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?

[ynotbrusum]

Surely, but the only one (lager) permitted by BJCP to have diacetyl expression is the Czech pale lager, I believe.  I know you know!

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?

You are likely blind to it at low levels, as am I and possibly a hefty slice of the population.  That is why I say that I detect it by mouthfeel and work backwards.  It was only through a tasting class by a well known local BJCP judge that I was able to determine that.  Seibel and others sell a tasting off-flavor kit to assist beer judges in gaining acuity toward common faults, diacetyl being one of them.

As to your own beer - a forced diacetyl test can be run, which will help in detection:

https://www.youtube.com/watch?v=LmYUAkUVUZg

[Village Taphouse]

I have had some examples of Pilsner Urquell that SCREAMED diacetyl.  Some cans and draft versions were very noticeable.  Some bottles were better.  When I drank it in and around Prague it was much, much cleaner. 

[Bel Air Brewing]

I have had some examples of Pilsner Urquell that SCREAMED diacetyl.  Some cans and draft versions were very noticeable.  Some bottles were better.  When I drank it in and around Prague it was much, much cleaner.

While in Prague, and Plzen (visiting the brewery), we never noticed any diacetyl. When in Frankfurt, I always went for Czech beer vs German beer.
The only off flavor noted in bottles here is an old, cardboard taste. Simply from not being a fresh beer. This trait is shared with many imports, unless you can snag a 6 pack that is only 3 months past it's packaging date.

[denny]

I have had some examples of Pilsner Urquell that SCREAMED diacetyl.  Some cans and draft versions were very noticeable.  Some bottles were better.  When I drank it in and around Prague it was much, much cleaner.

While in Prague, and Plzen (visiting the brewery), we never noticed any diacetyl. When in Frankfurt, I always went for Czech beer vs German beer.
The only off flavor noted in bottles here is an old, cardboard taste. Simply from not being a fresh beer. This trait is shared with many imports, unless you can snag a 6 pack that is only 3 months past it's packaging date.

Depends on where you buy it. I can get fresh, well treated PU, Czechvar/Budvar here. All exhibit diacetyl. Is it possible that you have trouble picking it up? That's not uncommon.

[Bel Air Brewing]

I have had some examples of Pilsner Urquell that SCREAMED diacetyl.  Some cans and draft versions were very noticeable.  Some bottles were better.  When I drank it in and around Prague it was much, much cleaner.

While in Prague, and Plzen (visiting the brewery), we never noticed any diacetyl. When in Frankfurt, I always went for Czech beer vs German beer.
The only off flavor noted in bottles here is an old, cardboard taste. Simply from not being a fresh beer. This trait is shared with many imports, unless you can snag a 6 pack that is only 3 months past it's packaging date.

Depends on where you buy it. I can get fresh, well treated PU, Czechvar/Budvar here. All exhibit diacetyl. Is it possible that you have trouble picking it up? That's not uncommon.

I had no trouble detecting it in my beer. We had a couple batches that were loaded with diacetyl. Luckily, they were fixable and turned out very good in the end.

The butter flavor in Pilsner Urquell must be very subtle. Yes, maybe below my sensory threshold.