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Old 04-12-2003, 10:28 PM
Measure for Measure Measure for Measure is offline
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Pressing Scientific Issue: Do Pump-Caps Preserve Soda Fizz?, Part II

There is a device called Fizz-Keeper, which allows the user to pump compressed air into soda bottles, thereby allegedly "preserving the fizz". I am curious about this item's effectiveness.

A recent thread discussed this issue; I would like further details.

(1) There are anecdotal accounts (including my own) that the fizz-keeper does indeed work. It is not necessary to add further casual observations. (I will not object if someone wants to bump this thread from page 3 though. )

(1a) Going beyond mere impressionism, if somebody wanted to test one of these devices, how would the fizziness be measured? Could it be measured using ordinary household items?

(2) The aforementioned thread and this website suggests that the Fizz-keeper should not work, since "the escaping gas can be pushed back into the liquid only by forcing more molecules of that particular gas (in this case carbon dioxide) into the space above the liquid."

(2a): Just to clarify: if you pumped pure oxygen at 100 atmospheres into a soda bottle's headspace, this would have no effect on the liquid's long run ability to carry CO2, right?

(2c): I understand that the amount of CO2 in ordinary air is inconsequential.

(3) The Journal of Chemical Education (Howald, Reed. The Fizz Keeper, a Case Study in Chemical Education, Equilibrium, and Kinetics J. Chem. Educ. 1999 76 208. ) claims the following:
Quote:
Increasing the pressure of CO2(g) will restore carbonation, but an increase in pressure adding air should not affect the equilibria. It can and does, however, affect the kinetics-the rate at which a new equilibrium is established. Thus the Fizz Keeper is effective for storage of resealed pop containers for hours, but not for periods of weeks or months.
I'd like a little elaboration on this point. Does "hours" mean 2 hours, 48 hours or what? No WAGs needed. And why the heck would the kinetics be affected? (And what does that mean anyway?) http://jchemed.chem.wisc.edu/Journal...eb/abs208.html

(3a) Regarding kinetics, how many times should the Fizz-keeper be pumped?

(4) Bonus question: Why is CO2 used to make soda fizzy, rather than any other gas? (Hmmm. Helium might be diverting.)
----
To summarize, I want to know whether the Fizz-keeper really works, and I want the answer to be scientific, Gaad dang it.

Disclaimer: I lack a background in chemistry or physics, so I won't be able to moderate this thread very well.
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Old 04-12-2003, 11:21 PM
Ficer67 Ficer67 is offline
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once the seal is broken on a bottle or a can of soda (doesn't matter) the "fizz" begins to escape. Even if you pump air into the bottle or can, the container will not be able to hold the pressure because the seal was broken. The compressed air will escape, and the "fizz" will escape a little later.
  #3  
Old 04-13-2003, 12:24 AM
Squink Squink is offline
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(4) Why CO2 ?
CO2 is a good choice for making fizzy drinks, because not only does it dissolve in a liquid, like other gases, but also reacts with water to form carbonic acid, and its ions. Thus the equilibrium concentration of CO2 in the air ,vs solution, lies towards more total carbonates in solution than with a ideal, nonreactive gas. If you charged a bottle of Soda with helium, rather than CO2, most of the gas would come out in one great bump immediately upon opening. However, the kinetics of CO2 <->HCO3- <->CO32- are slow (~seconds), so not only do you end up with a lot more potential gas dissolved when you use CO2, but it comes out more slowly.

The CO2 <->HCO3- <->CO32- equilibrium depends on temperature, pH, and yes, pressure. Data on the pressure effect is hard to come by, however before the last thread on this subject crashed-and-burned, I did find a site that gave a few figures. Canít locate it now, but itís a small, nonzero, effect.

With plastic bottles at least, there may be a simple explanation for why some the pump seems to work for some people:
The soda pop is supersaturated with respect to CO2 (all those carbonates...).
The bottle is flexible.
When you close the bottle you tend to squeeze it.
This results in a low initial air-pressure inside the bottle, and walls that are easy for increased pressure to deflect.
Since the pop is supersaturated, carbon dioxide gas will come out of solution, until the point where the walls of the container supply enough rigidity for pressure to build and stop the process.
Using a pump lets you use air, rather than fizz to make the container rigid.

If thatís not too clear, think about what would happen if you quickly pulled a vacuum on a soda bottle, and then sealed it. Youíd end up with a normally inflated bottle with a pressurized atmosphere of nearly pure CO2 above the pop. - Flat soda.
  #4  
Old 04-13-2003, 06:57 PM
Measure for Measure Measure for Measure is offline
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Terrific post, Squink.

_To Recap_

To the extent that bottle rigidity is the goal, it appears that one or two pumps should be sufficient.

Another method of promoting fizz duration is to keep the bottle well chilled, as Squink and one of my links pointed out.
---
We are still left with a strictly empirical question: does the fizz-keeper really work in a meaningful way? For example, how does it compare with efforts to keep the beverage well-chilled?

_Methodological Concerns_
Looking over Squink's links, it appears that H2CO3 is a weak acid (carbonic acid), so a precise ph measurement, _might_ proxy for fizziness. But perhaps there are better methods.
  #5  
Old 04-13-2003, 08:43 PM
kanicbird kanicbird is offline
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Quote:
(4) Bonus question: Why is CO2 used to make soda fizzy, rather than any other gas? (Hmmm. Helium might be diverting.)
An interesting aside, Guneiss Stout (Beer) uses nitrogen as well as the natural fermenting CO2.

I think the reason we use CO2 is because the fermenting process produced it, when we figured that out we could carbonate any beverage.
  #6  
Old 04-13-2003, 08:51 PM
Chronos Chronos is online now
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Suppose that we put high-pressure air into the bottle, along with the pop. Presumably, that would then force some nitrogen and oxygen into solution, as well, would it not? And any gas in solution would "fizz" when the bottle is opened, correct? So if these pumps increase total gas concentration, does it really matter whether the gas is CO2?

As an aside, I've also seen gizmos which take a small compressed CO2 tank, like you might use for a BB gun, and carbonate or recarbonate drinks, and those would obviously increase CO2 solution, but that's not what the OP is asking about.
  #7  
Old 04-13-2003, 11:21 PM
Measure for Measure Measure for Measure is offline
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Ok, Chronos, but Squink claims that CO2 and H2O forms carbonic acid, which allows the beverage to stay fizzy for more than a few seconds.1 So the effects of lightly pressurized Nitrogen and Oxygen should be shortlived and (I would guess) small.

Admittedly, O2 and Nitrogen are more reactive than helium and kanicbird implies that Nitrogen reacts with stout in some way (though I speculate that it does not react that much with water).2
---
I'm curious about those CO2 gizmos. I wonder whether they are cost-effective.

1flowbark disavows any knowledge of chemistry.

2Ha! I knew Guiness had a different mouthfeel than other carbonated beverage products!
  #8  
Old 10-02-2011, 08:54 PM
Measure for Measure Measure for Measure is offline
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Fizz Keeper: Don't bother, IMO

Update! Update! Update! Update! Update! Update! Update! Update! Update! Update!

Wikipedia has a decent treatment of the issue: http://en.wikipedia.org/wiki/Fizz_keeper

Although Fizz Keeper affects the kinetics the effect lasts hours, not days. Plus, Rohrig (2002) notes that the seal of an ordinary cap is better than that of Fizz Keeper. As a result, ordinary caps tend to beat the Fizz Keeper over a 24 hour period. Experimentally.

If you want to extend fizziness, concentrate more CO2 in the headspace of the bottle. In practice, this might mean transferring contents to a smaller bottle, thereby making the headspace smaller.


Seltzer makers now run about $100, btw. I doubt whether they are economical, but they are probably entertaining. A 2009 Amazon review notes that obtaining CO2 canisters in the US can be expensive in practice.

2007 NYT Review: http://www.nytimes.com/2007/10/10/dining/10fizz.html

I have set aside my Fizz Keeper.

Last edited by Measure for Measure; 10-02-2011 at 08:55 PM.
  #9  
Old 10-04-2011, 09:52 PM
AaronX AaronX is offline
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Aww, I bought one of those to try and make carbonated water.
  #10  
Old 10-05-2011, 12:36 AM
Measure for Measure Measure for Measure is offline
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Seeing as FizzKeeper effectiveness has been debunked IMHO, I hereby declare Seltzer maker experiences to be on topic. Please indicate your country, as I understand availability of C02 canisters can vary.
  #11  
Old 10-05-2011, 12:53 AM
Boyo Jim Boyo Jim is offline
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I must admit I never thought of why CO2 and not other gasses are used. Should anyone care to experiment, I will volunteer to test soda pressurized with nitrous oxide.
  #12  
Old 10-05-2011, 12:59 AM
Mangetout Mangetout is offline
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Quote:
Originally Posted by Ficer67 View Post
once the seal is broken on a bottle or a can of soda (doesn't matter) the "fizz" begins to escape. Even if you pump air into the bottle or can, the container will not be able to hold the pressure because the seal was broken. The compressed air will escape, and the "fizz" will escape a little later.
I realise this was written a long time ago, but I'm very surprised this statement wasn't challenged. The seal on a screw top bottle consists of the top being screwed on to the correct torque. Why would this not be repeatable by screwing the lid back on? (Obviously not possible with cans)

Last edited by Mangetout; 10-05-2011 at 01:00 AM.
  #13  
Old 10-05-2011, 01:12 AM
Boyo Jim Boyo Jim is offline
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The gas has to be pumped back into the bottle with the seal in place. So you can't re-pressurize the drink, and then put the original screw top back. The switch would depressurize it all over again.
  #14  
Old 10-05-2011, 01:21 AM
Mangetout Mangetout is offline
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Quote:
Originally Posted by Boyo Jim View Post
The gas has to be pumped back into the bottle with the seal in place. So you can't re-pressurize the drink, and then put the original screw top back. The switch would depressurize it all over again.
Sure, but that's about the contents of the bottle - Ficer67's post appears to be saying something about the mechanical configuration of the closure.
  #15  
Old 10-05-2011, 02:44 AM
Measure for Measure Measure for Measure is offline
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Quote:
Originally Posted by Mangetout View Post
I realise this was written a long time ago, but I'm very surprised this statement wasn't challenged. The seal on a screw top bottle consists of the top being screwed on to the correct torque. Why would this not be repeatable by screwing the lid back on? (Obviously not possible with cans)
Well, it was basically ignored. I can assure you that fizz keeper does keep some air in, though the seal of ordinary caps is apparently better. Once resealed, CO2 is added to the headspace from the soda until a new equilibrium is reached. It's the opening and closing of the bottle that vents the CO2, if I understand it correctly.
Quote:
Originally Posted by Boyo Jim
I must admit I never thought of why CO2 and not other gasses are used. Should anyone care to experiment, I will volunteer to test soda pressurized with nitrous oxide.
Well, you could start with whipped cream from a canister...

This site helpfully lists the solubility of various gases in water. Argon, methane, hydrogen and Helium don't appear to dissolve particularly well. The gases that do are typically poisonous or noxious: examples include chlorine gas, hydrogen sulfide, ammonia and sulfur dioxide.
  #16  
Old 10-05-2011, 10:44 AM
bump bump is offline
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The bottle's in equilibrium before you open it, but once it's open, it's the partial pressure of CO2 that would determine how much CO2 comes out of solution into the space in the top of the bottle.

Adding more pressurized air wouldn't change that partial pressure much at all, so the soda keeper wouldn't work too well.
  #17  
Old 10-05-2011, 08:24 PM
ZenBeam ZenBeam is offline
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We had a fizz-keeper many years ago, but it didn't help, and may have actually made things worse. In the thread linked to in the OP, Ike Witt wrote
Quote:
Originally Posted by Ike Witt
If you want to maintain the fizz in an opened 2 litre bottle of soda, all you have to do is squeeze in the sides a little. Pour yourself a glass, and then squeeze in the sides so the liquid is near where it would be when the bottle is new. The next day, the bottle will have expanded out to its original size and the pop will still fizz. AFAIK, you want to limit the area that the CO2 can expand into.
I now think Ike Witt is mostly correct, but that his reason why may be wrong.

I bought a Jokari Soda Dispenser, which is screwed onto the pop bottle as soon as it's opened. In the picture, you can see the flexible tube that dips into the pop. I cut that off. The pop got agitated flowing through that tube when it was being poured, making it lose its fizz in the glass when poured. Without the hose, I just tip the bottle before pushing the trigger. Pours much better, without foaming up in the glass. I also have to cut off the ring of left-behind bottle cap material on each bottle for it to make a good seal, which is a bit of a pain.

Anyway, I expected the bottle would inflate overnight each night, over the coarse of a whole bottle. It re-inflates once or twice, after pouring 10-12 ounce glasses, but after that, the bottle stays indented, so there's basically just atmospheric pressure from then on. When I'm near the end, the bottle is very dented in in the middle, and I have to hold it upside down, and use my whole arm to squeeze the bottle to get any out.

I've gone on vacation for a week with a half to two-thirds full bottle, come back with the bottle still not fully inflated, but with some fizz still in the pop. More than I'd have if I just sealed the pop with the lid, or used the fizz-keeper.

For most of the bottle, there's no pressure above atmospheric, so just squeezing the bottle to remove air should work just as well. I have never tried this, however.

I suspect that a big part of what helps it keep fizz in is that there isn't any air in the bottle, and that Oxygen or Nitrogen dissolving into the pop makes the CO2 come out more readily. Writing this post, it just occurred to me it's also possible that having the bottle squished reduces the interface area between the pop and headspace, and that this reduces the transfer of CO2 out of the pop. I'll try adjusting how I squish the bottle to minimize the interface area.
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Old 10-05-2011, 08:42 PM
RearEchelon RearEchelon is offline
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Maybe I'm underthinking, but wouldn't pressurized air above the surface of a liquid make it "harder" for the CO2 to escape and thus keeping more in solution? Kind of like raising the "boiling point?" Or am I just way off the mark?
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Old 10-08-2011, 12:54 AM
Balthisar Balthisar is offline
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Quote:
Originally Posted by Squink View Post
If thatís not too clear, think about what would happen if you quickly pulled a vacuum on a soda bottle, and then sealed it. Youíd end up with a normally inflated bottle with a pressurized atmosphere of nearly pure CO2 above the pop. - Flat soda.
Well, actually no. I've actually measured this at home in Michigan, and damn it, I don't have all my notes. At home I make beer, soda-pop, and carbonated water, and for the last two, I use weight as an indicator of percent carbonation.

(Side note: the setup is dirt cheap, and virtually free to operate. Consider 20 pounds of CO2 [food grade spec'd, but even the welding stuff is already food grade] is only about $18, and lasts forever.)

So to "pull a vaccuum" on a half-empty soda-pop bottle, just squeeze it until the soda rises to the top. Cap it. Some of the CO2 will leave solution, and the bottle will fill, but it's only a minute quantity of gas. Enough of the gas is still in solution so that it won't go flat. Note: this is pretty much as opposite as one can get from the idea of a FizzSaver type of device.

With a FizzSaver, the added pressure doesn't stop the CO2 from leaving solution. Rather you end up with atmospheric gas in the solution, and you don't want that.
  #20  
Old 10-15-2011, 12:23 AM
Measure for Measure Measure for Measure is offline
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Quote:
Originally Posted by RearEchelon View Post
Maybe I'm underthinking, but wouldn't pressurized air above the surface of a liquid make it "harder" for the CO2 to escape and thus keeping more in solution? Kind of like raising the "boiling point?" Or am I just way off the mark?
I was going to leave this for somebody with some chemical background, but since nobody has jumped in...

The concentration of CO2 in the headspace of the bottle affects the equilibrium quantity of CO2 dissolved in the water. That's consideration #1.

The air pressure in the headspace (as well as the temperature of the liquid) affects the speed at which the system attains equilibrium. That's consideration #2. The technical term for this appears to be, "the kinetics" and I suppose that it's what you were referring to. But this is something that is relevant for hours, not days -- or even 1 day according to measurements. See Squink's older post for the science and my reference to Rohrig (2002) for the empirical observations.

IANAC (I am not a chemist). Corrections and headsmacks are invited, as appropriate.
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Old 10-15-2011, 09:07 AM
ZenBeam ZenBeam is offline
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I can tell you, from observation before I had that soda dispenser mentioned in my last post, that my pop bottles would not reach equilibrium in only one day. They would be noticeably harder if they went two days without opening them again.

YMMV if you keep your bottles on the door. Then the extra jostling will tend to make it reach equilibrium faster. (So don't do that!)
  #22  
Old 11-20-2016, 11:47 AM
Channing Idaho Banks Channing Idaho Banks is offline
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I'll defer to Click and Clack the tappet brothers. I remember on car talk they did an experiment and figured out that the best way to conserve the CO2 in your soda bottle is to put the screw cap back on as fast as possible. They didn't mention anything about squeezing the bottle
  #23  
Old 11-20-2016, 12:44 PM
watchwolf49 watchwolf49 is offline
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Click and Clack as a citation ???

How do I delete my account here?

Last edited by watchwolf49; 11-20-2016 at 12:45 PM. Reason: Need answer fast ...
  #24  
Old 11-20-2016, 01:28 PM
Bill Door Bill Door is offline
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Quote:
Originally Posted by Measure for Measure View Post
I was going to leave this for somebody with some chemical background, but since nobody has jumped in...

The concentration of CO2 in the headspace of the bottle affects the equilibrium quantity of CO2 dissolved in the water. That's consideration #1.

The air pressure in the headspace (as well as the temperature of the liquid) affects the speed at which the system attains equilibrium. That's consideration #2. The technical term for this appears to be, "the kinetics" and I suppose that it's what you were referring to. But this is something that is relevant for hours, not days -- or even 1 day according to measurements. See Squink's older post for the science and my reference to Rohrig (2002) for the empirical observations.

IANAC (I am not a chemist). Corrections and headsmacks are invited, as appropriate.
Yeah, that's pretty close to it. The carbon dioxide will come out of solution until it reaches equilibrium with the carbon dioxide in the headspace. The equilibrium concentration varies with the temperature and pressure. Pressurizing the headspace with air will not help retain carbonation because there isn't enough CO2 in the air to have much of an effect. The pressure in the headspace will be the sum of the partial pressures of the gases in that headspace.
  #25  
Old 11-20-2016, 06:52 PM
jtur88 jtur88 is offline
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Simpler than a pump cap, would be a belt around the 2-liter bottle, with a shim that can be inserted between the belt and the bottle. Close the bottle tightly, slip in the shim, and tignten the belt to cave in the side of the plastic bottle. That will increase the pressure of the air inside, the same as a pump cap would, but much easier to fashion with relaxed tolerance for fitting adequately. A simple rubber gasket would also enable the cap to be replaced with a tight seal.

If a pump cap works, the shim-belt would work just as well.

Last edited by jtur88; 11-20-2016 at 06:53 PM.
  #26  
Old 11-20-2016, 07:19 PM
Gary T Gary T is offline
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I seem to recall reading/learning (somewhere) that a significant factor is the amount of space in the container not filled with liquid, which I gather is the headspace mentioned in some posts above. Thus squeezing a flexible bottle to get all the air out (but really for the purpose of not leaving much or any space for the CO2 to fill) or transferring to a smaller bottle with little or no headspace could be effective in minimizing loss of fizz, whereas simply adding air and pressure won't help much. In other words, the way to preserve fizz is to reduce or eliminate space, not to increase pressure. Does this sound like an accurate summation of the issue?
  #27  
Old 11-20-2016, 08:12 PM
voltaire voltaire is offline
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Some real pop science happening here!
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