Differences between samples after forced diacetyl test OTHER than diacetyl

[Noob_Brewer]

OK, sorry in advance if this is a long post. I have TWO main questions that I will put up front and then add context.

Question #1: with a forced diacetyl test, if diacetyl is present, will it be present in aroma, flavor, AND mouthfeel? are all three required to say the forced test "failed" or "passed"?
Question #2: what other changes in a sample (that was heated to ~145F for 25 minutes and then cooled back to room temperature) do you expect OTHER than diacetyl itself?

Context: I have a Doppelbock that has now been in the fermentor for 18 days. OG was 1.093, expected FG was 1.024. Pitched over 900B cells (2.0 pitch rate) and they were super healthy and fermentation kicked off while I was asleep but by my estimation was about ~12hrs post pitch. I let this chug away at 50F for just over 5 days before I started "inching" my way up in temps. I started ramping up towards the Drest when the tilt showed 1.038 which represented 80% of the expected attenuation range (1.093-1.024 = 69 points). At day 14 when I woke up, airlock activity was dead dead dead and the tilt was fluctuating between 1.021 and 1.020. So at the end of day 15, I pulled a hydro sample and hydro showed I was at 1.023 (the tilt was a little under the actual hydro reading). Its now been sitting at 1.020 (tilt readings) for 3 full days. So tonight I pulled another sample and did the forced diacetyl test to check before I crash this down in temps.

The forced diacetyl test procedures: I pulled a sample and split it between two small mason jars (~75ml each) and sealed them. One sample I kept at room temp and the other I put in a small pot in a water bath and heated it to ~145F on the gas stove. I kept it at ~140-145 for 25minutes (measured the water bath not the sample since it was sealed in mason jar). I then cooled the heated sample to room temp, put a piece of blue painters tape on the heated sample so I wouldn't mix them up. I then enlisted my 17yr old daughter to remove the tape from the heated/cooled sample but keep track of which is which so that my wife and I could do this diacetyl test blind.

Forced diacetyl test results:
Aroma: neither my wife nor I could smell ANY form of butter, movie popcorn, or any other descriptor of diacetyl there is. So in the aroma category there was ZERO diacetyl present.

Taste: again, we could not taste the obvious butter or movie popcorn indicative of diacetyl present in either sample BUT the two samples were still different. One sample (which later was shown to be the control sample) had more alcoholic taste - a warming effect but not boozy while the other (the heated/cooled sample) was easily smoother with 'almost' zero alcoholic warming effect so the maltiness was shining more without that alcoholic character. The heated and cooled same tasted more 'caramelly'. Keep in mind this is a doppelbock with just under 8% Caramunich I. This caramelly flavor was great! but I was thinking to myself - is this 'butterscotch'? which the escarpment labs utube video says can be indicative of diacetyl because beers with high amounts of crystal malt can be more 'butterscotch' than 'butter'. To me both samples tasted good though and neither were unpleasant.

Mouthfeel: There was a clear difference between the two but both tasted good. The sample that was heated/cooled (which I was still blinded to) had a nicer body but I kept asking myself - "is this slick?" It was definitely more velvety smoother than the control non heated/cooled sample.

So with these findings, I will re-iterate my two questions:

Question #1: with a forced diacetyl test, if diacetyl is present, will it be present in aroma, flavor, AND mouthfeel? are all three required to say the forced test "failed" or "passed"? - remember the aroma was definitively a 'pass' for diacetyl but taste and mouthfeel were essentially a "maybe?"

Question #2: what other changes in a sample (that was heated to ~145F for 25 minutes and then cooled back to room temperature) do you expect OTHER than diacetyl itself? - I think this question comes down to the fact that the forced diacetyl test essentially seems to age a beer so Im assuming the two samples ARE going to be different but the focus is on diacetyl detection and not that other effects of aging. Notably - the heated and cooled sample had minimal, if any, alcoholic warming which is why my wife actually liked it better.

I will end this post with, I have had one major diacetyl bomb in my young HB career and it was with a conan yeast (gigayeast) and it was obvious in aroma and flavor. Both my wife and I detected it. So I think we both knew what we were looking for in this test.

Looking forward to some responses to my two questions please and thank you in advance. Now I will shamlessly tag a couple HBT folks who have been great help to me these past couple years (and I fully respect their opinions) but any/all perspectives are welcome regarding these questions. @Dgallo @jdauria

EDIT: I will add that I used WLP833 the german bock lager yeast

 

[Dgallo]

OK, sorry in advance if this is a long post. I have TWO main questions that I will put up front and then add context.

Question #1: with a forced diacetyl test, if diacetyl is present, will it be present in aroma, flavor, AND mouthfeel? are all three required to say the forced test "failed" or "passed"?
Question #2: what other changes in a sample (that was heated to ~145F for 25 minutes and then cooled back to room temperature) do you expect OTHER than diacetyl itself?

Context: I have a Doppelbock that has now been in the fermentor for 18 days. OG was 1.093, expected FG was 1.024. Pitched over 900B cells (2.0 pitch rate) and they were super healthy and fermentation kicked off while I was asleep but by my estimation was about ~12hrs post pitch. I let this chug away at 50F for just over 5 days before I started "inching" my way up in temps. I started ramping up towards the Drest when the tilt showed 1.038 which represented 80% of the expected attenuation range (1.093-1.024 = 69 points). At day 14 when I woke up, airlock activity was dead dead dead and the tilt was fluctuating between 1.021 and 1.020. So at the end of day 15, I pulled a hydro sample and hydro showed I was at 1.023 (the tilt was a little under the actual hydro reading). Its now been sitting at 1.020 (tilt readings) for 3 full days. So tonight I pulled another sample and did the forced diacetyl test to check before I crash this down in temps.

The forced diacetyl test procedures: I pulled a sample and split it between two small mason jars (~75ml each) and sealed them. One sample I kept at room temp and the other I put in a small pot in a water bath and heated it to ~145F on the gas stove. I kept it at ~140-145 for 25minutes (measured the water bath not the sample since it was sealed in mason jar). I then cooled the heated sample to room temp, put a piece of blue painters tape on the heated sample so I wouldn't mix them up. I then enlisted my 17yr old daughter to remove the tape from the heated/cooled sample but keep track of which is which so that my wife and I could do this diacetyl test blind.

Forced diacetyl test results:
Aroma: neither my wife nor I could smell ANY form of butter, movie popcorn, or any other descriptor of diacetyl there is. So in the aroma category there was ZERO diacetyl present.

Taste: again, we could not taste the obvious butter or movie popcorn indicative of diacetyl present in either sample BUT the two samples were still different. One sample (which later was shown to be the control sample) had more alcoholic taste - a warming effect but not boozy while the other (the heated/cooled sample) was easily smoother with 'almost' zero alcoholic warming effect so the maltiness was shining more without that alcoholic character. The heated and cooled same tasted more 'caramelly'. Keep in mind this is a doppelbock with just under 8% Caramunich I. This caramelly flavor was great! but I was thinking to myself - is this 'butterscotch'? which the escarpment labs utube video says can be indicative of diacetyl because beers with high amounts of crystal malt can be more 'butterscotch' than 'butter'. To me both samples tasted good though and neither were unpleasant.

Mouthfeel: There was a clear difference between the two but both tasted good. The sample that was heated/cooled (which I was still blinded to) had a nicer body but I kept asking myself - "is this slick?" It was definitely more velvety smoother than the control non heated/cooled sample.

So with these findings, I will re-iterate my two questions:

Question #1: with a forced diacetyl test, if diacetyl is present, will it be present in aroma, flavor, AND mouthfeel? are all three required to say the forced test "failed" or "passed"? - remember the aroma was definitively a 'pass' for diacetyl but taste and mouthfeel were essentially a "maybe?"

Question #2: what other changes in a sample (that was heated to ~145F for 25 minutes and then cooled back to room temperature) do you expect OTHER than diacetyl itself? - I think this question comes down to the fact that the forced diacetyl test essentially ages a beer so Im assuming the two samples ARE going to be different but the focus is on diacetyl detection and not that other effects of aging. Notably - the heated and cooled sample had minimal, if any, alcoholic warming which is why my wife actually liked it better.

I will end this post with, I have had one major diacetyl bomb in my young HB career and it was with a conan yeast (gigayeast) and it was obvious in aroma and flavor. Both my wife and I detected it. So I think we both knew what we were looking for in this test.

Looking forward to some responses to my two questions please and thank you in advance. Now I will shamlessly tag a couple HBT folks who have been great help to me these past couple years (and I fully respect their opinions) but any/all perspectives are welcome regarding these questions. @Dgallo @jdauria

Hey brother. So I’ll answer #1 in a very simplistic way as two I’ve never even thought about or focused on so I have no answer for you

#1 with a force diacetyl test, if diacetyl or diacetyl precursors are present you Should certainly be able to smell it. You should also clearly taste it.

 

[Noob_Brewer]

Hey brother. So I’ll answer #1 in a very simplistic way as two I’ve never even thought about or focused on so I have no answer for you

#1 with a force diacetyl test, if diacetyl or diacetyl precursors are present you Should certainly be able to smell it. You should also clearly taste it.

Thanks for the reply man. Yeah, I always thought that if diacetyl was present during a force test, you would definitely be able to smell it and I definitely could not. Its the taste/mouthfeel that were different as the beer definitely changed after heating/cooling. So just trying to separate "normal" changes due to the test compared to detecting diacetyl. I "think" I am good to go on this but just wanted to see what others thought before I crashed this. Thanks again.

 

[Callacave]

Agreed with Dgallo. It just sounds like you're not quite familiar with the flavor or aroma of diacetyl, and it just comes with experience. If it's in your sample you should definitely be able to tell that there's a significant enough difference between them. I always find that the heated and chilled sample vs. the room temp sample is always a little different. It's probably just from the chemical reaction of heating up a sample will change the profile of a beer. You might be able to detect it more easily with an Ale yeast just after fermentation is complete.

 

[Noob_Brewer]

Thanks for your reply @Callacave I appreciate it. I think I do know what the flavor/aroma of diacetyl is....when its obvious lol. I did have one butter/popcorn bomb about a year and half ago in a NEIPA. But, I am unsure on how low my own threshold is for detecting it. I have had two other club members test it and they couldn't detect it either. Your point about the chemical reactions of heating up a sample changing the profile is very helpful to me though and confirms to me that the two samples, if both absent of diacetyl, will indeed taste different anyways. I have done a diacetyl test on a dark czech lager as well and the two samples were different as well.

But this doppelbock is a little harder to detect for me in flavor/mouthfeel although I am certain the diacetyl is not present in the aroma. As it is, this doppelbock is 9.3% and the heated/cooled sample appeared to drive off the alcohol warming a ton compared to control sample leaving a rich/malty flavor behind and has a nice caramelly flavor. Its that caramelly flavor that I just may be overthinking its "butterscotch" which may be diacetyl. So this is why I asked if diacetyl is present, it would be present in aroma and flavor in order for the test to "fail". Im probably just paranoid though lol. Thanks for your input.

 

[Noob_Brewer]

I think this quote from the link below is the reason why I had a hard time determining if the taste of diacetyl is present in my doppelbock.

"....though in both cases, you’ll want to be aware of how other flavors in your beer might be mimicking or masking diacetyl. Caramel (especially the sweeter variety created by low-Lovibond crystal malts) or toffee can often be mistaken for diacetyl, as can the richness of melanoidins from some character malts (melanoidin malt, Victory, Biscuit, Aromatic, etc.)."


https://beerandbrewing.com/hunting-for-diacetyl/