Constant Ruined Brews - Oxidised?

Hi Ankou

Been reading up on diacetyl rest, am I right in saying this involves raising the temperature at the end of fermentation to allow the yeast to clean up the diacetyl?

I live in SW London, it could possibly be my water supply is of a less-than-ideal composition. To be fair, that is one of the common denominators in all ruined batches too. Your suggestion to use bottled water next time is a good one so will probably do that too.

An Ankoù said:

I use swing top bottle (Fischer Tradition sometimes) and I've never had any problems with pressure leakage. I also use PETs regularly (Peregrino and Perrier) and, even after a year there's no pressure drop or oxidation issues. I can imagine that oxygen diffusion would be an issue for flat liquids like white wine for example put not when there's a healthy pressure of CO2 inside.

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I often wonder why people believe you can get gas diffusion going against a positive pressure or put simply why you can get atmospheric oxygen leaking into a pressurised beer bottle whether its PET or not. Its similar to water being unable to flow uphill. If the pressures are balanced that's different. But if anyone has proper evidence to the contrary please share it.

Devlin said:

Hi Ankou

Been reading up on diacetyl rest, am I right in saying this involves raising the temperature at the end of fermentation to allow the yeast to clean up the diacetyl?

I live in SW London, it could possibly be my water supply is of a less-than-ideal composition. To be fair, that is one of the common denominators in all ruined batches too. Your suggestion to use bottled water next time is a good one so will probably do that too.

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Absolutely, and I judge by your question that you, perhaps, haven't been doing that so that could be the butterscotch problem sorted.
See Sadfield's post above about mixed gases in the headspace. If it is metal pigmentation then it's happening when the metal goes to a higher oxidation level eg ferrous to ferric or cuprous to cupric (in the old terminology) I think the fact that the stain starts at the top of the bottle before eventually tainting the entire bottle indicates we've got that one nailed, too.
Won't know until you brew up another batch though. Good luck.

terrym said:

I often wonder why people believe you can get gas diffusion going against a positive pressure or put simply why you can get atmospheric oxygen leaking into a pressurised beer bottle whether its PET or not. Its similar to water being unable to flow uphill. If the pressures are balanced that's different. But if anyone has proper evidence to the contrary please share it.

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On a micro level some gas particles will move into the higher pressure area however the (overwhelming) net flow will be from high to low.

The reason for this is that gas particle motion is entirely random. "High pressure" simply means that there are more of them per unit area, increasing the likelihood of motion into lower pressure areas and making equilibrium the eventual resting state - though of course gas particles are never "at rest" moving as they are at several hundred metres per second.

A bit of a digression, sorry!

If you're using beer bottles then it should have around the base a measurement . on the 330ml bottle that I use it is 47mm. That is the height from the top that the bottle should be filled to for the correct volume of beer in the bottle. Whilst this is for trading standards it is also a useful guide to the right amount of beer to put in.

foxbat said:

On a micro level some gas particles will move into the higher pressure area however the (overwhelming) net flow will be from high to low.

The reason for this is that gas particle motion is entirely random. "High pressure" simply means that there are more of them per unit area, increasing the likelihood of motion into lower pressure areas and making equilibrium the eventual resting state - though of course gas particles are never "at rest" moving as they are at several hundred metres per second.

A bit of a digression, sorry!

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Thanks for that.
I understand what you have said and I accept that at the molecular level there might be some migration into the barrier material (e.g a rubber gasket or PET bottle) but I guess that will soon 'fizzle out' after a tiny distance due to the density of the barrier and so to all intents and purposes there will be no measurable movement across the barrier. If there was movement, on a practical homebrew level, the high pressure side would slowly decay since that is subject to a higher driving force, but that it something I have not noticed since I have stored beer in PET bottles for over a year without any perceivable loss of pressure.

Ok, so. For me after reading this thread I would suggest two things.

a) I think you are right that you are suffering from oxidation and you need to increase your bottle fill level and also your practises around reducing O2 pick up as much as possible. This will affect your beer but not as much as your describing.
b) I suspect you have a bacterial infection in your equipment. The way you describe the hop character diminishing and a bitterness developing suggests that you have something continuing to consume the complex sugars of your beer. Which only a bacteria could do.

I suggest (IMHO) that you replace all disposable elements of your fermenting and bottling kit (hose, plastic fermenter and maybe wand) and start again. And this time pay really close attention to clean and sanitisation after each brew. including the bottles. And if you can. For the first beer after you replace all of the above, if you can use new/diff bottles that would be better as the bacteria may be resident in your bottles as well.

terrym said:

I often wonder why people believe you can get gas diffusion going against a positive pressure or put simply why you can get atmospheric oxygen leaking into a pressurised beer bottle whether its PET or not. Its similar to water being unable to flow uphill. If the pressures are balanced that's different. But if anyone has proper evidence to the contrary please share it.

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Surely, because PET is permeable to both oxygen and CO2 (at variable, and low rates), then the bottle is not a closed system, so will always be trying to reach dynamic equilibrium with the external environment through a combination of Henry's Law and Fick's laws of diffusion.

https://en.m.wikipedia.org/wiki/Dynamic_equilibrium

Hoddy said:

Ok, so. For me after reading this thread I would suggest two things.

a) I think you are right that you are suffering from oxidation and you need to increase your bottle fill level and also your practises around reducing O2 pick up as much as possible. This will affect your beer but not as much as your describing.
b) I suspect you have a bacterial infection in your equipment. The way you describe the hop character diminishing and a bitterness developing suggests that you have something continuing to consume the complex sugars of your beer. Which only a bacteria could do.

I suggest (IMHO) that you replace all disposable elements of your fermenting and bottling kit (hose, plastic fermenter and maybe wand) and start again. And this time pay really close attention to clean and sanitisation after each brew. including the bottles. And if you can. For the first beer after you replace all of the above, if you can use new/diff bottles that would be better as the bacteria may be resident in your bottles as well.

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I think your right this is a bit more than oxidation. I fill my bottles straight from the tap in my new fermenter as the bottling wand doesn't fit the new tap. I have never had a problem.

Sadfield said:

Surely, because PET is permeable to both oxygen and CO2 (at variable, and low rates), then the bottle is not a closed system, so will always be trying to reach dynamic equilibrium with the external environment through a combination of Henry's Law and Fick's laws of diffusion.

https://en.m.wikipedia.org/wiki/Dynamic_equilibrium

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Thankyou for providing this information.
Whilst Henry's Law governs several processes important in brewing, mainly about CO2 levels in the FV before packaging, and pressurisation in vessels after priming, it appears to me that it only primarily concerns systems where there is no other driving force, including diffusion through a barrier where one side is at a higher pressure than the other.
And as far as I can see Ficks Law is the same concerning dp across a barrier. However Ficks Law clearly applies when there is little or no pressure driving force and as I have said I accept that some gas diffusion will occur over time to attempt to attain an equilibrium across say a PET bottle wall when the pressures are more or less equal.
So I don't really accept these references to change my understanding, and my view remains that on a practical macro level the amount of oxygen that diffuses from outside into a pressurised beer bottle through a PET bottle wall or a rubber seal over the time that most homebrewers utilise, will be so small as to be insignificant, certainly in relation to the amount of oxygen that finds its way into the packaged beer through air entrainment, surface exposure, and importantly those few mls that are left in the headspace of a bottle after filling, which is something commercial brewers address, but is outside the capability of most homebrewers.
But if you hold a different view that's fine by me, we should just agree to differ.

I wonder how @Druncan is getting on with his sulphite experiment as an oxygen scavenger?

Hi Devlin, do you keep the filled bottles at room temperature for a couple of weeks then move them somewhere cool, for a week or two before tasting?

Are you putting your dry hops in a muslin bag or just directly into the fermentation vessel?

edit (only read the first page so someone might have asked this already)

Found this a really informative read, however... I do exactly what @Devlin does. I bottle from the bottling wand, I don't fill the bottle, I tend to leave a lot of the neck empty and I use both clear and brown glass but I have never experienced what he's explaining. The only thing I seem to do differently is once bottled, I stored in the airing cupboard for 2 or 3 weeks and then move to the shed to cool for a further 2 weeks minimum... And that's where they live until the move to the fridge, the night before I want one.

if you bottle using jug and funnel method dissolved CO2 in foam fills the bottle in the top 2 to 3 cms so very little air in bottle - I have never had this problem.

But surely it is introducing oxygen in to the beer by jugging it in and the funnels have a natural swirling motion that will add loads of oxygen IMO

the baron said:

But surely it is introducing oxygen in to the beer by jugging it in and the funnels have a natural swirling motion that will add loads of oxygen IMO

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So please explain why the beer still tastes good.
Sounds to me like the urban myth about aeronautical engineers explaining how bumblebbees are unable to fly.

I put funnel into bottle then hold bottle at 45 degrees so there is no swirling or glugging in the funnel. As I bottle 3 to 4 days after yeast pitch there will be a lot of dissolved CO2 in the beer some of which will be released in the bottle right from the start, so as beer level rises in the bottle the CO2 will flush out air (which only contains 19% oxygen anyway). Baron - I was not detailed enough in my post 74 - sorry.

It's interesting that pouring wort is considered enough to oxygenate wort prior to fermentation, yet not enough to oxidise wort post fermentation.

I assume the oxygen in the wort starts the yeast going well and is then flushed out by the vast amount of CO2 produced.....