What contributes more to oxidised beer - Headspace or oxygen dissolving during transfer?

[Agentgonzo]

I've also read about the supposed "super oxidant" properties of ascorbic acid but only anecdotally on internet forums. Unless I notice it in my beer, or scientific evidence comes forth or a significant body of brewers go "I see the same" I'm going to ignore it as one of those wacky internet theories.

 

[hoppyscotty]

This is interesting if its not already been linked elsewhere. Not sure of the science/chemistry behind it.



Personally I have the means to keep the beer away from air and oxygen from fermentation right through to the glass so I do it for all beers as a point of best practice. Its easy and not a pain in the *** or particularly expensive to get yourself set up so why not?...just remove that variable from your process and you don't have to worry about it. I did experience oxidation before my ability to keep air away so it is a thing, but I tend to brew beers with heavy late addition hops and dry hopping so brewing the style of beers most susceptible to the issue. In fact there was one batch that I hooked upto my kegarator and forgot to purge the CO2 gas line after replacing the line and pushed the air that was in the line into the keg and the beer showed early signs of oxidation within a week in starting to change colour. I knew what I had done immediately and was a 'DOH!' moment but didn't think it would have an impact. Flavour wasn't impacted for a number of weeks after and by then the keg was almost done so not much beer wasted, but that shows what a small amount of air amounting to the volume a couple of feet of 3/16 gas line can do to a Homebrewed NEIPA. But since I have the ability to keep air totally away at all stages then I do. Why would you not?

 

[Hazelwood Brewery]

I’m going to suggest you may have answered your own question in your second post @Agentgonzo

During primary fermentation the yeast will use the dissolved oxygen that might already be in the wort. As long as a blanket of CO2 sits above the beer there should be no more oxygen getting into the beer.

If we could discount any process flaws, for example opening the fermenter to dry hop or exposing the beer to oxygen in the bottling bucket/keg, it’s more likely to be oxygen in the head space.

If we can’t assume the above then all bets are off because the root cause(s) could be multiple and diverse throughout your process.

Packaging is the area where I think the issues are all concentrated where oxidation is concerned and the subsequent storage conditions will be a big secondary factor affecting the rate of stalling.

 

[Agentgonzo]

But since I have the ability to keep air totally away at all stages then I do. Why would you not?

If you have the kit to do it, then there's no reason not to. For me, I don't have a CO2 setup so it's not easy for me, hence I need to take more care in other areas to guard against oxidation. A CO2 setup is costly and I don't have the space for it unfortunately.

 

[hoppyscotty]

Packaging is the challenge in that case. You can keep air out even with a plastic bucket fermenter but as soon as you start transferring to bottles or kegs then that is the challenge. One option would be to somehow capture the CO2 driven off from fermentation - maybe pipe into another sealed bucket or balloon/bag etc. A bit of creative thinking about how to purge a bottle with it and you're pretty much there. A bit more faff but at least you'll be doing what you can. But as others have said only an issue with very hop forward beers so plenty of delicious beers you can brew that are not so susceptible.

 

[Agentgonzo]

If we can’t assume the above then all bets are off because the root cause(s) could be multiple and diverse throughout your process.

You can keep air out even with a plastic bucket fermenter but as soon as you start transferring to bottles or kegs then that is the challenge.

This is kind of the direction of the issue (or non-issue??) that I was thinking about. If you have a CO2 setup, it's not too problematic. But if you don't (for whatever reason) then what is the simplest thing to tackle. If it's the headspace that is the major contributor, you can get around this by simple things like squeezing the air out of PET bottles. But if it's the transfer out of the fermenter/bottling bucket and into the bottle that picks up oxygen en-route, then you need to target the transfer and purging the headspace may be of negligible benefit. I honestly don't know which of the two contributes more to oxidation than the other.

 

[hoppyscotty]

Personally I think its the splashing and exposure as you transfer thats the main exposure risk. Squeezing the headspace out of the bottle will help of course and probably will reduce chances of the affects significantly, but exposure as you're pouring into the bottle will have an impact if a very hoppy beer as per my experiences when I forgot to purge a CO2 line. It doesn't take alot of air to make a difference and the air within the headspace will float on top of the CO2. I guess its a time at exposure issue so if you can do things quickly then that is best so long as you don't agitate stuff up too much and increase the surface area of the beer that is exposed.

My thinking was if you can capture CO2 from fermentation in a bag, then a quick squirt out of a hose and a second bottling wand into the bottom of the bottle will create a layer of CO2 in the bottom of the bottle so the beer delivered by the bottling wand will be delivered into a blanket of CO2 and as you fill the bottle the air will be pushed out of the bottle leaving the blanket of CO2 on top of the beer as long as you don't agitate things too much. This blanket of CO2 will then become your bottle headspace. Perfectly feasible with a few cheap materials and no reason why it wont be successful. The only challenge here is the size of the bag containing the CO2 at normal atmospheric pressure will be quite large.

Speaking with a brewer a few weeks ago with his cask beers that he just fills directly from the fermenter under gravity and open with no CO2 purging at all said the best thing is to drink it quickly!! Once the keg is tapped its a matter of days till the beer spoils, but that is usually not an issue in a busy pub.

 

[Hazelwood Brewery]

This is kind of the direction of the issue (or non-issue??) that I was thinking about. If you have a CO2 setup, it's not too problematic. But if you don't (for whatever reason) then what is the simplest thing to tackle. If it's the headspace that is the major contributor, you can get around this by simple things like squeezing the air out of PET bottles. But if it's the transfer out of the fermenter/bottling bucket and into the bottle that picks up oxygen en-route, then you need to target the transfer and purging the headspace may be of negligible benefit. I honestly don't know which of the two contributes more to oxidation than the other.

Why wouldn’t you target both? If for some reason you can only tackle one or the other, just do it. It will still be an improvement on doing neither.

It’s worth noting that highly hopped beers with lots of oats are affected more dramatically more quickly but you are seeing a representation of what happens to all beers.

 

[Agentgonzo]

Why wouldn’t you target both? If for some reason you can only tackle one or the other, just do it. It will still be an improvement on doing neither.

Call it academic curiosity. (obviously if you can tackle both, do )

 

[rbunsen]

I wonder if someone can explain to me the following ?
During bottle conditioning, where is the oxygen coming from for the CO2 that is produced ? Is it coming from somewhere else other than the dissolved oxygen or air at the top of the bottle ? Or does it just not use enough of it ?
If it is anaerobic respiration, the O2 would still need to come from somewhere, wouldn't it ?
I am just looking to be educated a little here.

 

[Agentgonzo]

Yeast doesn't need oxygen to ferment. In the fermenter or when bottle conditioning, the yeast converts sugar (glucose) into alcohol and carbon dioxide. No oxygen needed.

Anaerobic means "without air" (ie oxygen)

 

[Cwrw666]

I wonder if someone can explain to me the following ?
During bottle conditioning, where is the oxygen coming from for the CO2 that is produced ? Is it coming from somewhere else other than the dissolved oxygen or air at the top of the bottle ? Or does it just not use enough of it ?
If it is anaerobic respiration, the O2 would still need to come from somewhere, wouldn't it ?
I am just looking to be educated a little here.

The CO2 comes from the breakdown of carbohydrates which as the name suggests contained carbon, hydrogen and oxygen atoms.

 

[rbunsen]

Many thanks for both answers.

 

[An Ankoù]

I recall brewery visits in the 80s and seeing the bottling line, which took a line of bottles along a conveyer belt into a "black box" where they were filled and then the crown corks put on. I don't recall any references to oxidation or purging bottles in what was otherwise a very detailed explanation of the process. If the beer was then pasteurised then head space oxygen would react more quickly with the beer woudn't it?
I fill my bottles with a tube that goes from the tap to about a third of the way down the bottle. The beer splashes gently onto the priming sugar causing the beer to give off some of its dissolved carbon dioxide, pushing the gas content of the bottle up and out of the bottle- thus purging the bottle. It then gets capped. I imagine that's exactly the same thing that happened in the brewery's bottling line. I also recall that there was no mentioned of dry-hopping bottled beers. Dry hopping was for the casks, where a large pellet of compressed hops would be dropped into the cask before sealing it. All sorts of bottled beers have been around for hundreds of years, but this issue with "oxidation" is relatively recent. Are we to assume that a six-month old bottle of Bass, for example would have been horrible? Manet 1881, didn't seem to think so.

 

[DocAnna]

I wonder if someone can explain to me the following ?
During bottle conditioning, where is the oxygen coming from for the CO2 that is produced ? Is it coming from somewhere else other than the dissolved oxygen or air at the top of the bottle ? Or does it just not use enough of it ?
If it is anaerobic respiration, the O2 would still need to come from somewhere, wouldn't it ?
I am just looking to be educated a little here.

1 molecule Glucose (C6H12O6)-> 1 molecule Ethanol (2C2H5OH) + 2 molecules Carbon Dioxide (2CO2)
Most of the sugars in wort are disaccharides, e.g table sugar 'Sucrose' two simpler sugars like glucose and fructose chemically bonded together. So the first step is for these double sugars to be split by the yeast, then each of these simpler sugars is converted in several steps to a common intermediary called Pyruvate, then lastly to Ethanol. None of these steps require oxygen, but they do create two ATP molecules for every one of simple sugar. ATP is the universal energy currency of every living cellular organism on the planet.

It is the ATP that is produced that makes it worth the yeast's while going to the effort of converting the glucose/fructose.

I hope that makes sense.

 

[DocAnna]

I recall brewery visits in the 80s and seeing the bottling line, which took a line of bottles along a conveyer belt into a "black box" where they were filled and then the crown corks put on. I don't recall any references to oxidation or purging bottles in what was otherwise a very detailed explanation of the process. If the beer was then pasteurised then head space oxygen would react more quickly with the beer woudn't it?
I fill my bottles with a tube that goes from the tap to about a third of the way down the bottle. The beer splashes gently onto the priming sugar causing the beer to give off some of its dissolved carbon dioxide, pushing the gas content of the bottle up and out of the bottle- thus purging the bottle. It then gets capped. I imagine that's exactly the same thing that happened in the brewery's bottling line. I also recall that there was no mentioned of dry-hopping bottled beers. Dry hopping was for the casks, where a large pellet of compressed hops would be dropped into the cask before sealing it. All sorts of bottled beers have been around for hundreds of years, but this issue with "oxidation" is relatively recent. Are we to assume that a six-month old bottle of Bass, for example would have been horrible? Manet 1881, didn't seem to thing so.
View attachment 70565

The issue is heavily dry hopped beers - with no NEIPAs on that table. It is the concentration of reductones in the beer that determines whether oxidation is a significant thing or not. All beers will oxidise though, the issue is whether it affects the taste or other sensory perception of the beer. For beers without significant concentrations of reducing substances in them, the sensory perception of oxidation will in many cases be marginal.

 

[Cheshire Cat]

I recall brewery visits in the 80s and seeing the bottling line, which took a line of bottles along a conveyer belt into a "black box" where they were filled and then the crown corks put on. I don't recall any references to oxidation or purging bottles in what was otherwise a very detailed explanation of the process. If the beer was then pasteurised then head space oxygen would react more quickly with the beer woudn't it?
I fill my bottles with a tube that goes from the tap to about a third of the way down the bottle. The beer splashes gently onto the priming sugar causing the beer to give off some of its dissolved carbon dioxide, pushing the gas content of the bottle up and out of the bottle- thus purging the bottle. It then gets capped. I imagine that's exactly the same thing that happened in the brewery's bottling line. I also recall that there was no mentioned of dry-hopping bottled beers. Dry hopping was for the casks, where a large pellet of compressed hops would be dropped into the cask before sealing it. All sorts of bottled beers have been around for hundreds of years, but this issue with "oxidation" is relatively recent. Are we to assume that a six-month old bottle of Bass, for example would have been horrible? Manet 1881, didn't seem to thing so.
View attachment 70565

Look oxidation is like gluten and lactose intolerance they are new phenomenon people 60 years ago weren’t intolerant and neither was there any oxidation. I blame the hippy generation for all these problems.

 

[An Ankoù]

The issue is heavily dry hopped beers - with no NEIPAs on that table. It is the concentration of reductones in the beer that determines whether oxidation is a significant thing or not. All beers will oxidise though, the issue is whether it affects the taste or other sensory perception of the beer. For beers without significant concentrations of reducing substances in them, the sensory perception of oxidation will in many cases be marginal.

Point well made and well taken, but people are talking generally about beer and not just the sludgy tincture of hops, which, by rights shouldn't be called beer at all. I wonder what novice brewers think reading this. I don't think the OP had very-dry-hopped beers in mind in opening questions and I didn't get the impression that @chthon and @Nicks90 had those styles especially in mind in their contributions. Could very well be wrong, of course. Yes, all beers will oxidise with time. With some of the luscious barley-wine types- Thomas Hardy Ale, for example, this is an acceptable trade-off against the maturity that comes with ageing. Probably why they used a cork and why others (vintage brands no longer seen) that used corks covered them with wax.
My point being, let's not put the willies up the newbie by discussing the difficulties associated with a very niche product as if they were universal.
A stroppy answer to @DocAnna , in fact I love your posts and the really good references you link to.

 

[An Ankoù]

Look oxidation is like gluten and lactose intolerance they are new phenomenon people 60 years ago weren’t intolerant and neither was there any oxidation. I blame the hippy generation for all these problems.

Spot on @Cheshire Cat. In our day we didn't have oxygen and we had to make do with air. Full of pollution and smog it was. too, and stuff from blast furnaces and coal fires. Good wholesome air that made us strong and resilient.

 

[Agentgonzo]

I don't think the OP had very-dry-hopped beers in mind in opening questions

From an academic point of view, I was thinking about all types of beer, including very-dry-hopped beers. But from my own practical point of view, I don't brew many hoppy ales (and also have never had a problem with oxidation)