If you see an infection floating on the surface of your beer, then it is definitely an aerobic infection caused by too much oxygen in the headspace. If it isn't obvious on top but causes a vinegar smell, that is also aerobic. Other infections are harder to diagnose.
60L fermentor
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Lacto is anaerobic. So are many other problem microbes. Infection and oxidization don't go hand in hand. Plastic fermenters may be permeable/semi-permeable but if the unit is "sealed" then there should not be a problem as bacteria are vastly larger than an oxygen/co2 molecule and should not get into the fv in the amount of time fermentation and conditioning takes place. Positive pressure in the fv would keep nasties out in any case. Bad sanitization/cleaning procedures are the cause.(Or a leaky fv letting the germs in) Just my opinion. Happy to be shown to be wrong.
Yob
Hop to it
Don't you need to have it splashing or surface movement to transfer oxygen to liquid? (in enough to matter)
Pretty sure my fish don't get enough without the pump on...
Pretty sure my fish don't get enough without the pump on...
Yob
Hop to it
Yes, but how much head space?
Infection microbes are ubiquitous in the air. You have to open your fermenter to pitch yeast, that's enough to let infection in. I didn't say all infections were aerobic, just all the ones you see on the surface. (Lacto doesn't sit on the surface). Because they are on the surface they don't need the oxygen to dissolve, but of course oxygen dissolves easily without any splashing or disturbance, splashing just speeds things up. Some strange ideas in this thread, probably just people trying to stir things up.
pedleyr
Well-Known Member
What is a pity is that you seem to avoid answering the clear and direct questions put to you and instead choose to give vague monologues.
Yob
Hop to it
Anecdotal evidence still says that your fears arent justified. My 23lt of stout in my 50l FV tastes wonderful and still, surprisingly, hasnt turned into a green slimy mess... furthermore, it still has a positive pressure (diminishing I'll grant) a week after terminal gravity has been reached.
You surely arent suggesting that oxygen can force its way into a positive pressurised vessel?
You surely arent suggesting that oxygen can force its way into a positive pressurised vessel?
Yob
Hop to it
What is the problem with my post exactly?
I have certainly read your posts... I just don't get how oxygen can 'force' it's way into a vessel full of C02 at a higher pressure than atmospheric.
I have certainly read your posts... I just don't get how oxygen can 'force' it's way into a vessel full of C02 at a higher pressure than atmospheric.
TheWiggman
Haters' gonna hate
I said I signed out of this but I can't help myself.
That was my argument too Yob but it's not 100% correct. In the atmosphere we have ~21% oxygen at 1 atmopshere (duh) or around 101 kPa. That makes the partial pressure of O2 in the air 101 x 0.21 = 21 kPa for all intents and purposes.
If you have 100% CO2 inside the fermenter, there is 0 kPa of oxygen inside it.
Essentially the law of partial pressures states that each gas will seek a difference of pressure in respect to that gas itself. So the difference in this case is 21 - 0 = 21 kPa. The oxygen will try to get in as though it's applying 21 kPa of pressure on the fermenter.
NOTE that as oxygen transfers (and likewise so will nitrogen, argon and whatever else is around us), the difference drops and the rate of transfer drops too. As more oxygen gets in there, less oxygen tries to get in there.
So you can't say "400 cc/day" or whatever because the difference is not constant. And plus 400 cc/day would make a 20l head space the same as air after 4 days. So that's not even close. The 'cm3-mil/m2/24hr' unit off the website that previous posters are referring to is a nothing unit as far as I'm concerned. cm^3-mil doesn't line up with other units for this same problem in other examples, so I'd be disregarding it completely.
I'm still maintaining it's not a concern for home brewing over short (a couple of weeks) periods.
The ONLY reason I can think that you wouldn't want more headspace is because you will have more air in the fermenter to start with, which could potentially contain more nasties that could spoil the beer. The risk here is, in my opinion, too low to be genuinly concerned about. That judgement is up to each individual brewer. Greg.L certainly won't risk it, I will.
Signing out again...
That was my argument too Yob but it's not 100% correct. In the atmosphere we have ~21% oxygen at 1 atmopshere (duh) or around 101 kPa. That makes the partial pressure of O2 in the air 101 x 0.21 = 21 kPa for all intents and purposes.
If you have 100% CO2 inside the fermenter, there is 0 kPa of oxygen inside it.
Essentially the law of partial pressures states that each gas will seek a difference of pressure in respect to that gas itself. So the difference in this case is 21 - 0 = 21 kPa. The oxygen will try to get in as though it's applying 21 kPa of pressure on the fermenter.
NOTE that as oxygen transfers (and likewise so will nitrogen, argon and whatever else is around us), the difference drops and the rate of transfer drops too. As more oxygen gets in there, less oxygen tries to get in there.
So you can't say "400 cc/day" or whatever because the difference is not constant. And plus 400 cc/day would make a 20l head space the same as air after 4 days. So that's not even close. The 'cm3-mil/m2/24hr' unit off the website that previous posters are referring to is a nothing unit as far as I'm concerned. cm^3-mil doesn't line up with other units for this same problem in other examples, so I'd be disregarding it completely.
I'm still maintaining it's not a concern for home brewing over short (a couple of weeks) periods.
The ONLY reason I can think that you wouldn't want more headspace is because you will have more air in the fermenter to start with, which could potentially contain more nasties that could spoil the beer. The risk here is, in my opinion, too low to be genuinly concerned about. That judgement is up to each individual brewer. Greg.L certainly won't risk it, I will.
Signing out again...
Yes, I should have looked up the permeability figures for ldpe which is what glad wrap is made of I think.Greg.L said:
As you said, it probably lets is a lot more oxygen.
This only weakens your argument even more.
I just don't understand how it is even possible to make beer without rampant infection letting that much oxygen in using glad wrap.
And seeing as though you can, comparing headspace in a large and small sealed fermenter allowing a small fraction of the oxygen in is trivial.
I think the units are good. volume/thickness/area/time. I don't know what other units you could use.TheWiggman said:
They are probably some sort of maximum pressure differential permeation that tapers off anyway meaning the actual amount of oxygen is nowhere near the amount stated.
I agree, on a home brewing scale over a short time there is not a problem using glad wrap or a sealed fermenter.
pedleyr
Well-Known Member
What are you talking about?Greg.L said:
The truth of course is that there's nothing wrong with the post. You should withdraw the aspersions you were trying to cast by saying what you have.
Play the issue, not the man, like everyone else here is.
Grott
Beer Embalmer
All I can say from all this science is that all the oxygen effected beers are the ones that taste great and the ones not, are crap!?
AndrewQLD
RED ON WHITE IPA
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I assume greg.l was referring to a post that has been removed for offensive language, however since it wasn't removed within 30 seconds of it being posted he chose to question our ability to do our job.pedleyr said:
Greg, sometimes we don't see a post and it takes a report to be lodged to bring it to our attention, when that happens the post is acted upon as soon as we see it.
drsmurto
Well-Known Member
As a scientist who is paid to research the impact of oxygen in wine (amongst the many hats I wear) there are a few points that need clearing up.
During active fermentation, gladwrap, or no lid is fine, not perfect but in a homebrew situation, ok. Once fermentation slows down the gas laws that have been bandied around will come back to haunt you. There is nothing to stop oxygen getting back in to your fermenter as there is no measureable positive pressure. I've fermented many times with gladwrap, it domes during active fermentation and then collapses well before fermentation is complete. As others have pointed out, plastic is not an oxygen barrier. The sooner beer is transferred to keg/bottle, the lower the risk of oxidation.
Ask any winemaker/brewer who does this for a living whether they would leave wine/beer exposed to air post-fermentation. Any amount of headspace will contain oxygen due to the partial pressures discussed previously. Yes, even in wine which has a lower pH, higher ethanol content and vast amounts more naturally occurring anti-oxidants plus the ubiquitous addition of sulphite in large quantities, is very susceptible to oxidation once fermentation is complete. Winemakers go to great lengths topping up wine in storage and actively removing oxygen from the headspace, the best way to do so is to reduce the amount of headspace itself so wine is stored in vessels as close to capacity as physically possible. Stainless steel vessels with rubber seals. Beer is a sitting duck by comparison.
I recently stored wine in a 1000L HPDE plastic 'cube'. In 6 weeks, despite removing the oxygen in the headspace using dry ice (CO2) daily, sitting in a 0C room, the sulphite content dropped dramatically (41mg/L free SO2 to 25mg/L). Why? Oxygen was getting in to a sealed plastic container and reacting with the sulphite. Imagine a similar situation with a beer, cold conditioning in a cube/jerry can. No sulphite to protect it.
In working in this area I control oxygen levels down to parts per trillion and to do so requires a lot of effort and positive pressures in ss vessels. As I mentioned, there is no positive pressure in a fermenter or at least not anyway near high enough to prevent oxygen from getting in to your fermenters.
Despite flushing my anaerobic chambers in the lab down to <1ppt oxygen using nitrogen, and storing under a positive pressure of nitrogen all the time, I still measure an increase in oxygen concentration within days. They are flushed back down to <1ppt weekly. We measure the daily increase in oxygen in sealed glass wine bottles under a variety of closures and they all allow oxygen in. Yes, even screwcaps.
Using beer judging results to justify this is laughable. As someone who is also BJCP Certified the 'training' is non existent. Taste a few beers, answer a few questions and you get qualified. Let's not even go in to how many orders of magnitude easier it is now. I'd wager large amounts of money that the vast majority of beer judges, myself included, would fail a simple blind judging test we put wine sensory panellists though. Beer judging is a subjective and all results should be taken accordingly.
Using the open fermenters as evidence? Please. How long do they allow beer to sit in those fermenters? A few days of fermentation and they will be protected from oxygen by transferring to sealed vessels.
Hats off to GregL for attempting to help fellow AHBers out, I don't know why he bothers giving the response.
And with that, I'll disappear back in to the ether.
During active fermentation, gladwrap, or no lid is fine, not perfect but in a homebrew situation, ok. Once fermentation slows down the gas laws that have been bandied around will come back to haunt you. There is nothing to stop oxygen getting back in to your fermenter as there is no measureable positive pressure. I've fermented many times with gladwrap, it domes during active fermentation and then collapses well before fermentation is complete. As others have pointed out, plastic is not an oxygen barrier. The sooner beer is transferred to keg/bottle, the lower the risk of oxidation.
Ask any winemaker/brewer who does this for a living whether they would leave wine/beer exposed to air post-fermentation. Any amount of headspace will contain oxygen due to the partial pressures discussed previously. Yes, even in wine which has a lower pH, higher ethanol content and vast amounts more naturally occurring anti-oxidants plus the ubiquitous addition of sulphite in large quantities, is very susceptible to oxidation once fermentation is complete. Winemakers go to great lengths topping up wine in storage and actively removing oxygen from the headspace, the best way to do so is to reduce the amount of headspace itself so wine is stored in vessels as close to capacity as physically possible. Stainless steel vessels with rubber seals. Beer is a sitting duck by comparison.
I recently stored wine in a 1000L HPDE plastic 'cube'. In 6 weeks, despite removing the oxygen in the headspace using dry ice (CO2) daily, sitting in a 0C room, the sulphite content dropped dramatically (41mg/L free SO2 to 25mg/L). Why? Oxygen was getting in to a sealed plastic container and reacting with the sulphite. Imagine a similar situation with a beer, cold conditioning in a cube/jerry can. No sulphite to protect it.
In working in this area I control oxygen levels down to parts per trillion and to do so requires a lot of effort and positive pressures in ss vessels. As I mentioned, there is no positive pressure in a fermenter or at least not anyway near high enough to prevent oxygen from getting in to your fermenters.
Despite flushing my anaerobic chambers in the lab down to <1ppt oxygen using nitrogen, and storing under a positive pressure of nitrogen all the time, I still measure an increase in oxygen concentration within days. They are flushed back down to <1ppt weekly. We measure the daily increase in oxygen in sealed glass wine bottles under a variety of closures and they all allow oxygen in. Yes, even screwcaps.
Using beer judging results to justify this is laughable. As someone who is also BJCP Certified the 'training' is non existent. Taste a few beers, answer a few questions and you get qualified. Let's not even go in to how many orders of magnitude easier it is now. I'd wager large amounts of money that the vast majority of beer judges, myself included, would fail a simple blind judging test we put wine sensory panellists though. Beer judging is a subjective and all results should be taken accordingly.
Using the open fermenters as evidence? Please. How long do they allow beer to sit in those fermenters? A few days of fermentation and they will be protected from oxygen by transferring to sealed vessels.
Hats off to GregL for attempting to help fellow AHBers out, I don't know why he bothers giving the response.
And with that, I'll disappear back in to the ether.
