Diacetyl, help me figure it out

[WDT]

I've read the "Hold the butter" thread, wanted to ask the question again.

My last 3 batches have been overwhelmingly buttery and full tasting. The diacetyl shows up after they've been chilled and carbonated. They've all been IPAs too. I would like your help to pinpoint the cause.

First the beers:

Beer #1: Single Hop Citra IPA
1.071/1.010 IPA, US-05 (Double pitched 2 packets) Fermented 66F first 48 hours, held at 68F for 11 days. Dryhopped at 68F for 10 days. Total ferment time: 23 days.

Beer #2: Centennial/Cascade IPA
1.074/1.016, WLP007 (3L Starter) Fermented 62F first 24 hours, ramp to 67F for 11 days. Dryhopped for 6days at 68F. Total ferment time: 18 days.

Beer #3: Single Hop Centennial IPA
1.077/1.020, WLP002 (3L Starter) Fermented 62F first 24 hours, ramp to 68F for 12 days. (Dryhopped at the same time as kegging).

Final gravity was measured by taking 2 samples 3 days apart, with the exception of the Centennial IPA, I took one more gravity reading to make sure 1.020 was going to be the finishing gravity of that one.


My process:
I ferment in glass 6g glass carboys. Soak them in oxiclean overnight, rinse with water and store till brew day. Then I rinse with starsan liberally during brew day and dump sanitizer right before cooled wort goes in (on top of some foam).

They are visibly clean and then sanitized.

I rack using a visibly clean and star san soaked autosiphon. Same thing with a visibly clean and starsan soaked wine thief.

My kegs are soaked usually in hot oxiclean then rinsed with water and star san, stored filled with CO2 until use. I run star san out of the dip tube, but don't always disassemble them completely.

My theories:

Theory 1: Dirty racking equipment
I'm not super gentle with the auto siphon or thief and it sits on top of my table to air dry after each use. I'm thinking this might be the culprit... not sure if any one has ever experienced it.

Theory 2: Dirty Keg
Could a keg filled with CO2 sitting for about a month warm harbor something? My cleaning practices haven't changed and this has only been a problem in the last 3 batches.

Theory 3: Not letting the yeast clean up
Not letting it sit long enough?

Can I rule out a dirty keg or racking equipment as a source of diacetyl?

 

[daveooph131]

Yes you can rule out sanitation.

 

[insanim8er]

It can be an infection or a sign of yeast strain. Have you tried doing a D rest?

 

[Yooper]

Since it's only showing up after the beer is kegged, it leads me to consider that bacterial contamination, notably pediococcus, is the probable cause.

Can it be the beer lines? Or, if you take the beer off of the tap, and try a sample, is it in the kegged beer?

I think dismantling the keg (takes less than 5 minutes) would be a good way to start to troubleshoot.

I noticed that in a couple of bars I've been to that have icky lines they have diacetyl-laden beer.

 

[insanim8er]

This is a good read: http://www.draymans.com/articles/arts/03.html

Causes of diacetyl in beer:

High pitching temperature >22º even if the chilling is set at normal fermenting temperature.

High fermentation temperature; or runaway fermentations.

Pitched too little yeast (at least 1% slurry).

Pitched too much yeast (old, tired yeast cells, early flocculation).

Oxygen exposure during primary fermentation, secondary fermentation, at transfers, or at packaging.

Crash cooling of beer at the end of primary fermentation without including any diacetyl rest.

Insufficient time allowed for warm conditioning for sufficient diacetyl reduction.

Type of yeast strain used – some strains like Yorkshire Square fermentation strains (Old Speckled Hen) produce pronounced, but not unpleasant diacetyl levels in the beer.

Too early yeast flocculation and settling in the primary ferment.

Strains of Lactobacillus spoil beer by souring, producing turbidity and diacetyl. Diacetyl is generated by a different mechanism to that produced by brewer’s yeast. It most probably involves the condensation of “active acetaldehyde” and acetyl co-enzyme A. Pediococcus damnosus is especially common in breweries. It is particularly prevalent as a spoilage organism in beers fermented at low temperatures. Spoilage results mainly from the production of diacetyl. Other bacteria that produce diacetyl include Enterobacteriaceae and Obessumbacterium proteus.

 

[WDT]

Since it's only showing up after the beer is kegged, it leads me to consider that bacterial contamination, notably pediococcus, is the probable cause.

Can it be the beer lines? Or, if you take the beer off of the tap, and try a sample, is it in the kegged beer?

I think dismantling the keg (takes less than 5 minutes) would be a good way to start to troubleshoot.

I noticed that in a couple of bars I've been to that have icky lines they have diacetyl-laden beer.

I just bought new lines, they are a year old and this would be a good time for me to upgrade to 10' lines over my 5'. I clean them out every other keg with BLC. They are discolored though, and I've never taken apart the disconnects or the faucets.

I'm going to do a serious cleaning this weekend.

This is a good read: http://www.draymans.com/articles/arts/03.html

Causes of diacetyl in beer:

High pitching temperature >22º even if the chilling is set at normal fermenting temperature.

High fermentation temperature; or runaway fermentations.

Pitched too little yeast (at least 1% slurry).

Pitched too much yeast (old, tired yeast cells, early flocculation).

Oxygen exposure during primary fermentation, secondary fermentation, at transfers, or at packaging.

Crash cooling of beer at the end of primary fermentation without including any diacetyl rest.

Insufficient time allowed for warm conditioning for sufficient diacetyl reduction.

Type of yeast strain used – some strains like Yorkshire Square fermentation strains (Old Speckled Hen) produce pronounced, but not unpleasant diacetyl levels in the beer.

Too early yeast flocculation and settling in the primary ferment.

Strains of Lactobacillus spoil beer by souring, producing turbidity and diacetyl. Diacetyl is generated by a different mechanism to that produced by brewer’s yeast. It most probably involves the condensation of “active acetaldehyde” and acetyl co-enzyme A. Pediococcus damnosus is especially common in breweries. It is particularly prevalent as a spoilage organism in beers fermented at low temperatures. Spoilage results mainly from the production of diacetyl. Other bacteria that produce diacetyl include Enterobacteriaceae and Obessumbacterium proteus.

Thank you for the good read, I usually pitch at a cooler temp than i'm going to be fermenting at. I'm going to try a thorough cleaning and go from there. I just picked up a new autosiphon as well as new beer lines, cheap insurance.

I'm going to rule out yeast for now, since US05 is considered a clean yeast.