Just tapped a German ipa, all German malts, German hops and German ale yeast fermented at 63°f dry hopped 2x once in fermenter and once in keg. Tasted… diacetyl !!!, everything is perfect but a taste of butterscotch interfering with all the other good flavors. So I made a rookie mistake, I rarely use Pilsner malt, but used 7.5lbs for this recipe but did a 60 mun boil and not a 90 min. My question is will the butterscotch increase in time or will it fade over time?
It will only increase with time, until all of the precursor (alpha-acetolactate) has been converted to diacetyl. Many possible reasons for diacetyl in beer (lots of online resources for this). They’re mostly yeast-related issues, not malt issues. Using pilsner malt, or any other malt for that matter, doesn’t cause elevated diacetyl. (You might be thinking of DMS?)
Edit: One cause of diacetyl is a Pediococcus infection in the tap line. Your beer might be clean, but if there’s pedio in the line, you can get diacetyl from the pour. I’d perhaps start your troubleshooting by putting a clean tap line on the keg and tasting what comes out.
Diacetyl has nothing to do with pilsner malt. However, be aware that hops contain enzymes, so much that your dry hops will cause some unfermentable sugars to become fermentable, leading to effects like this one where you are experiencing diacetyl because the yeast is still working. Yeast eats diacetyl. If you keep the beer warm for about 3 weeks before drinking, the yeast should eat all the diacetyl and fermentable sugars and then you can chill and enjoy a butterscotch-free beer. It will disappear with age, just needs a few weeks. Link to brand new research on “The Freshening Power of Hops” (and this effect is not only from Centennial or Cascade, but almost all hops):
https://ir.library.oregonstate.edu/downloads/bc386q38t
Cheers.
Ha! “In contrast to previous thought…” she says in this “brand new” research… If you go back to the 19th century, providing amylase to ensure a complete secondary fermentation was the principal reason given for dry hopping, followed by providing tannin to aid in clarification by precipitating proteins, with any aroma or flavor contributions merely an incidental (unavoidable?) side effect. And yes, they let the beer stand for some time to complete the process before tapping. That should work here.
As stated, the malt had nothing to do with the diacetyl. Likely a temp issue or yeast issue. Can you give some specifics?
I use a glycol chiller on a conical, I don’t think it’s a temp problem, fermented at 63° and raised to 68° after 10 days. I did not do a starter I used 3 smack packs of wyeast. I sampled beer 3 times now. And now I can’t tell if it’s creamed corn or butterscotch. The good thing is I entered this into a local Homebrewers contest so I will get to the bottom of it. Thanks for all the replies!
Thank you dmtaylor for the link
Did you pitch your yeast at 63F or below that? Sometimes if you pitch warm then the yeast can produce more diacetyl which can remain in the beer if the beer is then cooled slowly down to a lower ferment temp.
I actually pitched at 78°! I made a mistake. I chilled with ground water, then pitched yeast. Instead of what I meant to do was chill with ground water move fermenter to garage and then chill with glycol chiller to 61°f then pitch. So I messed up and pitched yeast right after groundwater. I immediately started chilling with glycol and had it down to 61°f in 15 mins.
I doubt that’s your problem (though you should be concerned about yeast shock). If the beer tasted clean prior to dry hopping and racking then most likely oxidation caused the diacetyl. Introduction of oxygen post fermentation is the most common cause of diacetyl popping up after packaging. Even dumping hops into your beer will introduce oxygen, the hops pull o2 in with them. Be very careful on how you rack and dry hop post fermentation.
Let it rest for a few weeks, you need to let the yeast consume the diacetyl to reduce it to acetoin. If the rest does not do it, reinvigorate the cake or repitch with fresh culture. Next, get your hands on a sample of industrial ALDC and put a drop of that in your fermentation, it’ll do what the yeast does during diacetyl rest.
I have some good news. I over reacted, jumped the gun, you name it! My German ipa is pouring and tasting perfect out of the tap! I guess it was just young and needed another week. I usually do all my IPAs with safale 05. So I used wyeast German ale with this and fermented cold at 62° so I guess it just needed more time. I made a few mistakes on this beer and I guess I was overly worried… but looks like mistakes really didn’t do much harm. CHEERS 
That’s great news! I force diacetyl test all my lagers and many ales at 160 for 1 hour. When they show signs of diacetyl I let them sit for another 5 days or so and almost always the diacetyl is gone. Sometimes you just need to give the yeast a little more.
FYI I wouldn’t all 62 degrees “cold” for a German Ale yeast. That’s about the right temp. 56 would be on the cold side.