Off flavour, diacetyl?

[Kudzu]

Need some help identifying an off flavour in one of my beers. I'm inclined to think it's diacetyl, though not having any experience identifying off flavours, I've really got no idea. I wouldn't call it butterscotch as diacetyl is often described, but more a honey/caramel, the aroma is also quite strong. Not unpleasant but it's masking all the hop flavour/aroma. (If anyone in Launceston is good with this stuff I'll happily bring you a bottle to try)

Bit of information on the brew:

OG: 1.048

JW Pale Ale 90%
Wheat 5%
Dark Crystal 5%

Hopped with Cascade and Galaxy, don't think the schedule's relevant but can post if someone thinks it is.

Double batch BIAB - 39 litres
Mash 90 mins @ 66C, mashout 75C
Boil 60 mins

Chilled with immersion chiller to 25C - I can usually get under 20C, but with the warm weather this was as low as it wanted to go.

Split the batch into two fermenters and put in fridge.

Pitched Bry-97 in one batch and US-05 in the other (1 packet each), both re-hydrated to manufacturers specs. Temp on the STC (probe strapped to one fermenter under piece of stubby holder) was 22C. (warmer than I would have liked, but thought it was better to get the yeast in there).

Fermented with STC set to 17C for two weeks, then crash chilled at 1C for 5 days.

There was a ~10 hour power outage during active fermentation, but I've got no idea how hot the brews got as when I got home from work the power was back on and temp was reading 17C

The off flavour is present in both beers but is far more pronounced in the BRY-97 one. You can still taste the hops in the US-05.

My thoughts on possible causes:

1. Warm pitching temp
2. Power outage causing beer to get too hot
3. Fermentation temp? I've never actually calibrated the probe on the STC, have a scentific mercury thermometer on the way though.
4. Infection

Any other thoughts?

 

[manticle]

If it's slightly sweet and masking other flavours then it could indeed be diacetyl. There is also a closely related chemical called 2-3 pentanedione which has a honey-like character.

There is a good podcast featuring charles bamforth talking about vicinal diketones (vdk) their presence in beer and how to avoid or remove them.

http://www.youtube.com/watch?v=JoC0BgeH0qE


There's also a thread on here somewhere on diacetyl and us05.

This article explains a lot about what the chemicals are as well.

http://www.draymans.com/articles/arts/03.html

Without knowing or tasting the beer in question, I would guess it's a combination between slightly warm pitching and not maturing the beer long enough.

 

[Econwatson]

If you can get a hold of Samuel Smith's Organic Pale Ale, that helped me discover exactly what diacetyl tastes like, but also shows how it can be a really good flavour in the right measure!

 

[Kudzu]

Thanks for the info manticle I'll check it out, when you say not maturing long enough at what stage are you referring? Longer in the primary prior to crashing, longer cold crashing or longer in the keg? If so what would you recommend?

If you can get a hold of Samuel Smith's Organic Pale Ale, that helped me discover exactly what diacetyl tastes like, but also shows how it can be a really good flavour in the right measure!

Cheers, I'll see if I can track one down.

 

[Not For Horses]

I'd be more than happy to have a sample with you some time.
Just had a play around with an off flavours kit a few weeks ago.

 

[manticle]

Thanks for the info manticle I'll check it out, when you say not maturing long enough at what stage are you referring? Longer in the primary prior to crashing, longer cold crashing or longer in the keg? If so what would you recommend?

Longer in contact with good healthy, active yeast before any cold conditioning or transfer.

 

[Kudzu]

I'd be more than happy to have a sample with you some time.
Just had a play around with an off flavours kit a few weeks ago.

That would be great, will pm to organise something.

Will bring some pin-lock disconnects if you still wanted to try them on your keg. Also probably grab some spec malt if you have any in stock.

 

[probablynathan]

I'd be happy to taste as well, bring some along to the meetup. Diacetyl is one of the off flavours I can pick up quite easily, down to at least 19PPM.

 

[fletcher]

have a look at this PDF. helped me identify off flavours

http://aussiehomebrewer.com/topic/77520-alcohol-taste/?p=1122198

 

[whitegoose]

Mate I had a problem that sounds *exactly* like what you describe here. Strong aroma. Kinda sweetish or honeyish flavour, but not what I would call butterscotch. Absolutely no hop character (even when bucketloads of late hops were used) and it tends to notably worse day by day. I'm so stoked to hear that someone else has this problem!! Nothing I read about off flavours ever described what I was experiencing. I will be dead keen to hear what conclusion you come to.

I tend to only get it in pale beers, and definitely not in every beer, they just pop up occasionally.The first 3 times I got it were all in attempted pilsners, which lead me to believe it was diacetyl. To cut a long story short the things I tried over the last year or so included , longer primary fermentation, diacetyl rests, really long warm diacetyl rests, focussing more on mash pH and using salts and acidulated malt to get it right, completely refurbishing all the lines and fittings in my keg system, pulling my kegs and taps aart and cleaning them competely, buying a new fermenter.After all of this the problem seemed to go away until recently. I brewed a great Vienna Lager, then a brilliant Wit, but then a pale hopped-up Summer Ale which showed me the problem was back

I had a BJCP judge from the local beer club taste it and he was a little unsure. He did think diacetyl because it was sweetish and had a slick mouthfeel but it wasn't quite right... we talked about it a lot and then off hand he said he had heard that oxidisation can create a flavour that some people describe as honeyish which immediately pricked my ears up. Oxidaisation is also a runaway reaction that would get worse over time. After talking through my process we realised that I generally only filter pale beers (you know so they are super sparkling) and that I never purged my filter system with CO2 and I used gravity to push the beer through... A pleated filter that has just been sanitised potentially exposes the beer to a lot of O2 on the way though. in my mind, this is the problem. But my mate was still not 100% convinced.

So my takeaways from that session was:
1) I now use a carbon block filter to filter my mash water (Perth water is very chlorinated) .Probably not related but can't hurt!
2) If I filter, I now run CO2 through the whole system to push every ounce of oxygen out of there
3) If the problem is diacetyl, I have no idea what else I can do to get rid of it!!

Last weekend I kegged 2 new beers, both pale, an unfiltered aussie lager and a filtered kristalweisen and I am hoping that they are both good when I try them next weekend - they both tasted great out of the fermenter.

Anyway, there's my 2c. Interestingly I have experienced this problem using US-05 a lot, and also most recently using BRY-97 (I tried the latter after blaming the former).

Let us know how you go!!!!

 

[whitegoose]

There is also a closely related chemical called 2-3 pentanedione which has a honey-like character.

Veeeeery interesting....

 

[Kudzu]

Thanks whitegoose, that's some good info. It's actually receiving good reviews from friends and family, but I'm sure that flavour isn't supposed to be there (sometimes I think it might be just sweetness from the crystal), I do think it's mellowing a bit though (or maybe I'm getting used to it) and I'm starting to get some hops back.

Another thing that just occurred to me is our town water source has just been switched from an untreated mountain spring to chlorinated water from Launceston and I haven't been doing anything to remove the chlorine. I've done couple of other similar pale beers with this supply and haven't had this problem. We're moving soon and will have a private supply of fresh creek water and probably won't brew again before hand with this water.

Another interesting development is the off flavour becomes very pronounced when the beer drunk in combination with Kettle chili chips and starts tasting less like honey and more medicinal, so this has me leaning away from diacetyl and more towards chlorophenols.


I don't think mine could be coming from oxidation as the flavour was there a couple of hours after kegging from the primary.


Will bring a sample along to the meet-up next week and hopefully some more advanced pallets that mine might be able to pick up what it is.

 

[Ross]

Almost definitely diaceytl, guys....