Phenolic taste at the end of a keg.

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rrhynes
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Phenolic taste at the end of a keg.

Post by rrhynes » Mon Jul 01, 2019 3:08 pm

First a few lines on my process to zero in.
I've been brewing from grain successfully for years, favouring SO4 yeat because of it's flocculent properties.
I use modified King Kegs and Cornelius Kegs for storage.
At the end of secondary fermentation I crash cool and double fine using auxiliary finings then gelatine.
When this process is complete and the beer is crystal clear I rack to clean sanitised kegs.
I use CO2 bottles fitted with regulators to pressurise my King Kegs to 20 psi.
I then agitate to ensure carbonation is quickly complete, decouple the CO2, then begin consumption.
At this stage the beer is absolutely fine.

As the beer nears the the end of the keg, say about 15% of 5 gallons remaining, a slight phenolic taste occurs.
The beer is still crytal clear, has good condition, (because of CO2 topups), and is drinkable although not as good, as I cannot bear the phenols the Belgians love.

I have reasoned, (guessed), that this may be caused by a small volume of remaining beer sitting on a thin residual yeast bed which is still active and busy eating residual slowly fermenting sugars, (dextrins). If correct, this would presumably also mean that there are dead yeast cells there too, which could be bringing the phenol flavours.

I am still working on this problem, but write this post in case other brains know the problem and can speed up my solution.

Thanks in advance guys.

Bob.

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Re: Phenolic taste at the end of a keg.

Post by guypettigrew » Mon Jul 01, 2019 3:47 pm

From your post it seems as though this happens every time, every brew. Yes?

So, a few initial questions if I may.
  • How long is your beer in the King keg or Corny before you finish it?
  • How do you clean and sanitise your final vessels?
  • Do you treat your brewing water, and how?
  • How do you sparge, and do you check the gravity of the final runnings from the sparge?
It's unlikely your beer gets this flavour from sitting on the yeast cake at the bottom of the King keg or Corny. My beers can sit in the KK for a month or more and no phenolic taste appears.

We'll be able to sort this out for you somehow!

Guy

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Re: Phenolic taste at the end of a keg.

Post by Jocky » Mon Jul 01, 2019 3:52 pm

Which of these would you describe the phenols most like:

Cloves
Freshly cut grass
Medicinal/TCP
Peaty/Smoky
Rubber

?

Autolysed ('dead') yeast is more like marmite/slightly meaty flavour, so I'd be surprised if it was that in a beer that has been fined before going into the keg.

On an outside chance, do you dry hop in the keg? This can cause a grassy and slightly phenolic flavour at the end of the keg.

Otherwise normally I'd say phenols at the end of the keg would either be caused by a low level wild yeast infection.
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Re: Phenolic taste at the end of a keg.

Post by john luc » Mon Jul 01, 2019 3:53 pm

If you have a PH meter then test the beer to see if the level is rising.
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Re: Phenolic taste at the end of a keg.

Post by guypettigrew » Mon Jul 01, 2019 8:35 pm

Jocky wrote:
Mon Jul 01, 2019 3:52 pm
Otherwise normally I'd say phenols at the end of the keg would be caused by a low level wild yeast infection.
As Jocky says, hence the question about cleaning and sanitising.

Guy

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Re: Phenolic taste at the end of a keg.

Post by rrhynes » Tue Jul 02, 2019 11:57 am

Replies on Phenolic taste at the end of a keg.


Reply to Guy,
Thanks Guy replies embedded in your questions below.

From your post it seems as though this happens every time, every brew. Yes?

So, a few initial questions if I may.

How long is your beer in the King keg or Corny before you finish it? APPROX 2 WEEKS

How do you clean and sanitise your final vessels? THOROUGH WASHING AND RINSING FOLLWED BY A STAR SAN RINSE

Do you treat your brewing water, and how? SODIUM METABISULPHATE

How do you sparge, and do you check the gravity of the final runnings from the sparge? BATCH SPARGE

It's unlikely your beer gets this flavour from sitting on the yeast cake at the bottom of the King keg or Corny. My beers can sit in the KK for a month or more and no phenolic taste appears. GOOD, ALMOST CERTAINLY THIS RULES OUT THAT POSSIBILITY.

We'll be able to sort this out for you somehow!

Guy

Reply to Jocky,
Thanks Jocky, replies embedded in your questions below.

Which of these would you describe the phenols most like:

Cloves CLOVES
Freshly cut grass
Medicinal/TCP
Peaty/Smoky
Rubber

?

Autolysed ('dead') yeast is more like marmite/slightly meaty flavour, so I'd be surprised if it was that in a beer that has been fined before going into the keg. THANKS THIS IS HELPFUL BUT SEE BELOW.

On an outside chance, do you dry hop in the keg? This can cause a grassy and slightly phenolic flavour at the end of the keg. NOT CURRENTLY

Otherwise normally I'd say phenols at the end of the keg would either be caused by a low level wild yeast infection. I TOTALLY AGREE WITH THIS, WHICH IS WHY I MADE THE POINT ABOUT SMALL YEAST SEDIMENT UNDER A SMALL VOLUME OF BEER. IE YEAST DENATURING NATURALLY TO A BELGIAN STYLE BUT I HAVE NO EVIDENCE TO BACK IT UP.

Reply to Jon,
Thanks Jon, replies embedded in your questions below.

If you have a PH meter then test the beer to see if the level is rising. I do not have a ph meter but cannot see a link to cloves.

Reply to Guy Pettigrew
Thanks Guy, replies embedded in your questions below.

As Jocky says, hence the question about cleaning and sanitising. CLEANING AND SANITISING IS METICULOUS. ALSO I WOULD THINK THAT IF OTHERWISE, THE WHOLE KEG WOULD BE AFFECTED AND IT IS ONLY THE END OF KEG.

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Re: Phenolic taste at the end of a keg.

Post by guypettigrew » Tue Jul 02, 2019 4:51 pm

This is a lovely brain teaser!

You clearly sanitise your final vessels well, and the beer doesn't stay in them long enough to pick up any taint from autolysed yeast. Which wouldn't give a phenolic taste anyway. More a really nasty bitter Marmite taste.

Cloves and TCP towards the end of the two weeks definitely suggest a low level infection. Yeast or bacteria (obviously!), but I'm not knowledgeable enough to say which.

What this points towards is some nasties getting in your wort after the boil. Your wort will be sterile at the end of the boil, but all sorts of horrid things can happen afterwards. So, some more questions, if I may.
  • How do you cool your wort after the boil?
  • How do you transfer the wort from the kettle to the fermenting vessel? I'm thinking pumps and ball valves here. The latter are great at holding nasties in if they aren't dismantled and cleaned regularly.
  • What sort of room do you brew in? In other words, could it be somewhere which could harbour lots of bugs, such as a damp cellar?
  • How long does it take for visible signs of fermentation to show after you've pitched the yeast? if it's more than a few hours then any unwanted bugs will have time to multiply before the beer yeast can take over.
That'll do for now!

A post boil low level infection is looking most likely.

The other way round the problem, of course, is to drink the beer in a few days rather than a couple of weeks!!

Guy

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Re: Phenolic taste at the end of a keg.

Post by Cobnut » Tue Jul 02, 2019 5:14 pm

How often do you clean your pipes/taps? Maybe infection working its' way into the kegs via contaminated pipework or tap?
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Re: Phenolic taste at the end of a keg.

Post by Robwalkeragain » Tue Jul 02, 2019 5:27 pm

People make the mistake of thinking keg = sterile too - they’re not, just much less exposed to air than cask. Low temp will inhibit acetobacter too so you might notice other off flavours before vinegar.

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Re: Phenolic taste at the end of a keg.

Post by john luc » Tue Jul 02, 2019 7:08 pm

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http://www.nationalhomebrewclub.ie

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Re: Phenolic taste at the end of a keg.

Post by john luc » Tue Jul 02, 2019 7:10 pm

This is a good video to explain PH issues with sparge water that may explain some of your problems.
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Re: Phenolic taste at the end of a keg.

Post by Jocky » Tue Jul 02, 2019 10:17 pm

john luc wrote:
Tue Jul 02, 2019 7:08 pm
https://youtu.be/ITYuGVzM2aI
I understand where you're coming from - over sparging or high ph during the sparge leeches polyphenols (aka tannins).

But that doesn't explain why it would develop in the keg, and polyphenols caused in this way are not clove like in flavour at all.
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Re: Phenolic taste at the end of a keg.

Post by TheSumOfAllBeers » Wed Jul 03, 2019 9:14 am

Star San doesn't kill wild yeast. Unless you are using something more aggressive, such as bleach, iodine based sanitiser or steam pasteurising your kegs and lines, any wild yeast can survive in the kit and make its way to your kegs. It may not be noticeable post ferment but it can progressively develop in the keg.

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Re: Phenolic taste at the end of a keg.

Post by Jocky » Thu Jul 04, 2019 2:58 pm

I said that on the Milk the Funk Facebook group recently, and was pointed to this:
[youtube]https://youtube.com/watch?v=0JC9n50RdVo[/youtube]

Some people have done experiments and found it ineffective: https://www.homebrewtalk.com/forum/thre ... no.601403/

Purely anecdotal, but from threads on here and elsewhere it always seems like the people that have issues are using starsan exclusively. Perhaps that’s just because it’s so common.
Certainly doing a deep clean and then sanitising with a bleach or iodophor solution cannot harm.
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Re: Phenolic taste at the end of a keg.

Post by rrhynes » Tue Jul 09, 2019 9:53 am

Firstly thanks to everyone who has contributed such good replies to this thread.

Knowing as I do that wild yeasts bring phenols I looked again at my cleanliness. In particular I looked at my keg taps. The reasoning was if the tap harboured an infection, then it would not manifest in new beer that had just been placed in a sanitised keg immediately, i.e. it would take time. Moreover, full keg volume plus very small infection would mean it would be impossible to detect in taste at the start of keg. At the end of keg however things are very different, i.e. very small beer volume, sitting on an infected tap orifice. This would bring the phenolic taste for sure, providing the tap is infected.
To this end having sanitised the keg, but not sterilised it, I removed the tap from the barrel and smelt it, phenols!
Bear in mind this is an end of keg phenomena only, so sterilisation of keg and taps could be the answer.
Only after reaching this point have I had time to see the excellent additional replies to the thread, in particular:


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Re: Phenolic taste at the end of a keg.

Post by TheSumOfAllBeers » Wed Jul 03, 2019 9:14 am
Star San doesn't kill wild yeast. I DID NOT KNOW THIS OR HAD FORGOTTEN IT. IT’S REALLY IMPORANT TO KNOW. THANKS. Unless you are using something more aggressive, such as bleach, iodine based sanitiser or steam pasteurising your kegs and lines, any wild yeast can survive in the kit and make its way to your kegs. THIS IS MY BELIEF. It may not be noticeable post ferment but it can progressively develop in the keg. AGAIN I AGREE.
______________________________________________________________________

I am some distance from being able to test this out but will return to this post with the results when that data is in. In advance of that I am very hopeful that I have seen the last of it.

Again thanks to all.

Bob.

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