Infection?

[marky_mark]

Hey Guys,

I'm hoping someone may be able to shed some light on this situation. Recently I put down a Dortmunder export, and an American Brown Ale. Both were tasting fantastic throughout fermentation and right into the keg. However, after around two weeks in the keg the hop aroma has dropped off dramatically and I've started noticing a rather unpleasant aroma and flavour. I can best describe it as a sort of rancid vegetal aroma/flavour, similar to cooked cabbage. It could also be likened to what you get if you leave a large amount of hop and hot break trub out for a while after the boil.

Naturally with a vegetal aroma I thought DMS, but my process hasn't changed, still 90 min boils for light beers with a large portion of pilsner malt in the grist. Plus the brown ales doesn't have any pilsner malt in it, just traditional ale malt and various crystal malts. My second thought was an infection post fermentation. I have heard that some bacteria like coliform and hafnia can produce similar off-flavours to DMS, so I took a glass of the Dortmunder and left it out, warm, for a number of days to try and accentuate the issues. However, despite some oxidised flavours I really couldn't pick up any of the original vegetal flavours or aromas.

Potentially the bacteria could be anaerobic so I have tried bottling a sample of the beer to keep warm in an oxygen free environment and I'll see what transpires. In the mean time however, this issue has me puzzled. Can anyone shed any light on this... has anyone had a similar issue before?

Thanks guys,

Mark

 

[Screwtop]

Hey Guys,

I'm hoping someone may be able to shed some light on this situation. Recently I put down a Dortmunder export, and an American Brown Ale. Both were tasting fantastic throughout fermentation and right into the keg. However, after around two weeks in the keg the hop aroma has dropped off dramatically and I've started noticing a rather unpleasant aroma and flavour. I can best describe it as a sort of rancid vegetal aroma/flavour, similar to cooked cabbage. It could also be likened to what you get if you leave a large amount of hop and hot break trub out for a while after the boil.

Naturally with a vegetal aroma I thought DMS, but my process hasn't changed, still 90 min boils for light beers with a large portion of pilsner malt in the grist. Plus the brown ales doesn't have any pilsner malt in it, just traditional ale malt and various crystal malts. My second thought was an infection post fermentation. I have heard that some bacteria like coliform and hafnia can produce similar off-flavours to DMS, so I took a glass of the Dortmunder and left it out, warm, for a number of days to try and accentuate the issues. However, despite some oxidised flavours I really couldn't pick up any of the original vegetal flavours or aromas.

Potentially the bacteria could be anaerobic so I have tried bottling a sample of the beer to keep warm in an oxygen free environment and I'll see what transpires. In the mean time however, this issue has me puzzled. Can anyone shed any light on this... has anyone had a similar issue before?

Thanks guys,

Mark

What are you using to sample/serve - Clean your tap

Screwy

 

[Ross]

Like screwy I'd suspect your lines & tap.
You'd be amazed how your beers will improve by regular line cleaning, even if this isn't the issue.

Cheers Ross

 

[marky_mark]

For taking the samples I'm just using a picnic tap and a short length of 4mm beer line. It gets a run through with hot water every time I change kegs. Even so could that explain the loss of hop character or the vegetal flavour/aroma in the beer?

 

[T.D.]

For taking the samples I'm just using a picnic tap and a short length of 4mm beer line. It gets a run through with hot water every time I change kegs. Even so could that explain the loss of hop character or the vegetal flavour/aroma in the beer?

I doubt it. At a stretch I suppose if the lines were REALLY bad they could mask hop flavour, but from your description the lines sound fine.

Keeping your lines clean is important, but don't fall for the hype that you need to put heaps of expensive cleaning products through them on a regular basis. The most I ever do is put some napisan through them, leave it sit overnight, and then flush the next day with water then iodophor or peracetic solution. Too easy, and never had issues with dirty lines.

I cannot be 100% sure either way, but your problem doesn't sound much like dirty lines to me. To get the sorts of fairly obvious off flavours you are getting I would think the lines would have to be pretty dodgy, and it doesn't sound like they are from your description. How long have you been using the beer lines under the current regime? Have you had this same issue in other batches?

 

[marky_mark]

To date I have only detected this issue with the two beers I talked about (a Dortmunder and an American Brown Ale), but it may turn up in more... If it is an infection I'm thinking it may have come from my racking hose, which was used to transfer both beers into the keg post fermentation. However, I'm not certain that it is an infection yet...