A friend of my crunches his partially empty plastic soda bottles to keep the fizz in the drink longer.
He takes your basic 1 liter soda bottle that’s half empty or more and squeezes the sides near the top so it’s caved in a bit and then caps it. The idea being that the carbonation in the beverage now has less volume to fill so the pressure rises faster and ultimately keeps more fizz in the drink where it belongs.
For some reason this annoys me. When it’s his soda bottles I guess crunching them is his prerogative but he does it to mine too. Don’t worry, I know life has plenty of bigger things to worry about than this but it’s just one of those things that irks me. I don’t know…maybe I don’t like the aesthetic shape of the soda bottle to be ruined or something (frankly never gave it much thought).
So, does this work or will the pressure rise inside the bottle enough to ‘uncrunch’ itself?
The CO[sub]2[/sub] will come out of solution at lower pressure, causing your soda to go “flat”. To keep the fizzies in your lifting drink, make the pressure higher, not lower. This can be easily demonstrated with two half empty 2 liter soda bottles, one crushed in and one not.
I call foul. This thing he’s doing isn’t going to help.
His theory is sound, but his execution is fatally flawed. Let me explain…
If the pressure of the air in the sode bottle is high, the bubbles won’t come out of the soda. However, you are NOT keeping the pressure high just by putting a big dent in the bottle. It only take a little pressure to un-crunch the bottle, and then you’re right back to square one. If the
soda doesn’t have enough carbonation to pop the bottle back to normal, then it’s essentially flat already.
Unless he, like, duct-tapes the bottles in the crunched form, or does something else to keep the pressure from popping the bottle back to its normal shape, this doesn’t help at all.
-Ben
One can purchase a replacement cap that has a pump on it, to re-pressurize the bottles to help keep the CO2 in solution. They’re probably available at all major grocery stores, and they fit one-liter and two-liter soda bottles.
Also, show your buddy how FIRM those bottles are then they’re sold. That’s WHY they can stay on the shelf for a few months and still stay carbonated.
But, I suppose that if a two-liter bottle is finished w/in two days or so, then it probably all doesn’t matter too much.
If we assume the crunched bottle is still rigid enough to withstand any pressure increase from CO2 coming out of solution without un-crunching itself, then I believe the half-empty crunched bottle will retain CO2 in solution (AKA “stay fizzy”) better than the half-empty un-crunched bottle.
If true, the big driver of performance will be how thoroughly you can crunch the partly-emptied bottle. If you can remove 99.9% of the ullage space through crushing you’re going to preserve substantially all the fizz. Conversely, if in a half-full bottle you’re crunching out 5-10% of the ullage space you’re not going to have much effect at all.
Which also implies that, practically speaking, for almost-empty bottles you’re wasting your time.
I think somebody needs to start selling soda in rollable toothpaste tubes; that way you can keep all the fizz in all the time.
Back in the real world, 2L bottles are made that size to persuade the consumer that 2L is a reasonable single serving of the product. Not to encourage consumption in 6 servings spread over 10 days.
As the pump pumps in air, it’s raising both the total air pressure and the partial pressure of CO2 at the same rate. So as you increase the ullage pressure using air, you’re proportionally reducing the CO2 coming out of solution.
The question is entirely whether the pump can raise the total air pressure high enough to make a significant difference. I don’t know enough specifics about soda carbonation levels & pump output pressures and bottle strength to calculate that.
My bet is at the factory the ullage is filled with CO2, and given the fairly small CO2 percentage of the atmosphere, to keep the CO2 in solution with an air pump you’d have to pump in so much air pressure that the bottle would rupture before you got much effect.
Actually,. I’ve rigged the opposite, which does work. A tight belt around a 2-liter bottle. Then put the cap on tight with bottle in normal shape, and wedge a shim under the belt to increase the pressure inside. It’s “crunching” the bottle, but after sealing it, not before.
What works for me, (at least in my head) is I try not to jostle the bottle around to much.
When I pour, I pour very slowly and when I put it back in the fridge, I set it down very softly. Like it’s a bomb or something.
All they do is carbonate the soda slightly more than what they want, and after they put the cap on, it all comes to equilibrium at some pressure higher than ambient.
It’s basically the same thing that happens each time you open it and re-cap it. Some CO2 comes out of solution, but since the bottle’s closed, the system reaches equilibrium and no more carbonation is lost.
You’d have to basically be recarbonating the soda, or nearly so to get it to not eventually go flat. This would probably work, as would adding an appropriately small piece of dry ice.
Squeezing the bottle before sealing it will do nothing to preserve fizziness if the bottle remains perfectly rigid in its new configuration, and will hasten the loss of fizziness if the bottle is less than perfectly rigid.
Squeezing the bottle after sealing it will help, so long as you have some way of keeping it squeezed (like the belt with a shim).
Pumping in air will do nothing to increase or preserve carbonation (except to the extent that air contains trace amounts of carbon dioxide), but carbonation is not the same thing as fizziness. Any dissolved gas will cause fizziness, and even if nitrogen and oxygen are less soluble (and thus less fizzogenic) than carbon dioxide, they’ll still help some.
In my experience, using a cap with a pump makes the pop go flat faster, not slower. I suspect that the added pressure of N2 and O2 somehow makes the CO2 come out faster.
I don’t drink pop from 2 liter bottles any more, but when I did, I had a cap with a trigger handle that let me pour pop without opening the bottle after putting it on when I first opened it. I was the only one drinking it, and only had maybe 10 ounces per day. I’d have to squeeze the bottle to pour the pop. By the third or fourth day, the bottle wouldn’t inflate to full any more, so the head pressure was just the atmospheric pressure. The pop held a fizz well even then.
I’d expect that squeezing the bottle to remove air would work almost as well, since you’re reducing the amount of O2 and N2 that can displace CO2 (per my conjecture above). Also, as CO2 comes out of the pop, the partial pressure of CO2 will rise faster than if you have an uncrushed bottle, since there’s less gas volume. If you just replace the cap, or use an air pump, you’d have to have a lot of CO2 come out of the pop for the CO2 partial pressure to reach 1 atmosphere.
Good advice. A long time ago, we used to keep the pop on the door shelf. When we switched to putting it on the normal shelf, the bottle wouldn’t be nearly as hard the next day, presumably keeping more CO2 in solution.
Why not? If there’s less air space in a sealed bottle, then it will take a much smaller amount of CO2 coming out of solution to fill that space to a partial pressure in equilibrium with the CO2 in solution and it will happen at a higher partial pressure. So there would be more CO2 in solution, and more fizziness.
So, I think, squeezing a bottle so there’s less air space, and then sealing it, should keep in fizziness.
