Diacetyl test

[schmurf]

Out of curiosity, and an actual problem I'm sometimes struggling with, I thought I would try doing a forced diacetyl test, as explained on various places on the internet: take two samples from the brew, heat sample 1 to 70-ish degree (celsius) for 20-30 mins, let it cool, then compare the two samples.

But, what am I exactly expecting when doing the comparison? I know diacetyl should manifest itself as "buttery", but I'm always struggling with putting words on what I'm tasting/sensing. Doing this test on a beer I have fermenting now, a barley wine which been in fermenter for 11 days, seems to have stopped since 6 days at 1.025. I get a rather noticable difference when comparing the samples, but I wouldn't say sample 1, the heated one, tastes buttery... just different. So what should I expect? Should it be more or less the same for it to be good to go, or is a difference ok, as long it's not buttery?

 

[jdauria]

You should smell almost like a buttered popcorn aroma and taste it some...but if you swish the sample around in your mouth, if you get a slick, almost oily feeling in your mouth if diacetyl is present.

Have to say, I have brewed over 150 beers over last 12 years and knock on wood, have never had a diacetyl issue. I enter a lot of comps and never had a judge mention it, nor has the national ranked judge in my club. If you can control fermentation temps, raise temps up near the end of fermentation, don't rush the beer off the yeast so that the yeast can clean up after itself, it should not be an issue. Pitching yeast at the proper pitch rate helps also.

 

[schmurf]

Thanks, I wish I was able to put a word on what I'm tasting. This test sample didn't taste like buttered popcorn to me (but I haven't had popcorn for something like 30 years or so) and not like the off flavour I sometimes get either. So doing this test didn't make me any wiser unfortunally... the two test samples didn't taste the same, but I don't know if that's is to expect, regardless if it's diacetyl in the sample or not.

The problem I have occasionally is an off flavour that isn't noticable at kegging/bottling time, but is there after a few weeks when it's time to drink.

I do have fermentation control nowadays so I always ramp up temp at the end.

 

[hotbeer]

Search the web for homebrew off flavors. Read about some stuff other than the diacetyl which probably is the number one thing noobs focus on besides oxidation, but is probably unlikely to be an issue for homebrewers.

Reading about all the other things might at least give you the words to describe your off taste to us even if it doesn't give you the solution.

 

[schmurf]

Search the web for homebrew off flavors. Read about some stuff other than the diacetyl which probably is the number one thing noobs focus on besides oxidation, but is probably unlikely to be an issue for homebrewers.

Reading about all the other things might at least give you the words to describe your off taste to us even if it doesn't give you the solution.

Belive me, ever since I first encountered this off flavour I've been trying to find descriptions of it. I just can't put a name to the flavour, probably not because it's a particulary odd flavour, but because I suck at it... just as I suck at describing colours etc. Does it taste like cooked vegetables? Maybe. Does it taste like butterscotch? Maybe. Etc etc... my brain just either can't associate that flavour with those descriptors, or it can associate all of them.

I've had one fellow homebrewer suggesting DMS. I've had a beer judge telling me it's esters from fermentation. While both might be correct off course, I just can't accept it is any of that. There are too many things going on that contradict those suggestions. Fortunally it doesn't happen THAT often, but often enough for me to wanting to find out what the heck is causing it.

I've read that diacetyl shows up after kegging and knowing that I'm sometimes hurry things a bit too much I wanted to learn how to make a diacetyl test, and see if I can "force" getting the same off flavour.

 

[hotbeer]

Maybe instead of trying to brew yourself an example to taste so you know, just buy a Bud or whatever your favorite big brewery beer is and toss in some microwave buttered popcorn to see if that's the taste you have.

I've not actually ever tasted diacetyl myself and recognized it, but that's what I imagine it as tasting like. I also think that diacetyl is unlikely to be what you are experiencing unless you use a crap load of yeast and bottle as soon as fermentation is over.

But I have a lot to learn still and that's just a uneducated opinion that might change when I find different in the future.

 

[couchsending]

There are off flavor sensory test kits you can purchase through Morebeer and various other places. They’re not cheap but you can go in on one with some buddies or maybe suggest your Homebrew club purchase one or two and do some sensory training at the next meeting.

Some people are much more sensitive to certain compounds than others and some can’t pick them up at all.

Diacetyl can present itself in many ways. Aroma, flavor, and texture. In my experience in order to get to texture there has to be a ton of it.