Why does Coke go flat with ice?

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Geektastic

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#302981 8-Jan-2023 16:55

Over Christmas we had some Coke in 250ml cans, something we don’t usually have in the house.

Several times I went to have some and found that if I had ice in the glass, the Coke was essentially flat by the time I completed pouring the can.

I have had it more times than I can count with ice in bars and restaurants and it’s not flat then.

Why is it flat at home?

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#3018619 8-Jan-2023 17:15

because the warm coke mixed with the ice causes an instant release of carbon dioxide due to the difference in temperature, in the bars/restaurants it's chilled already so the ice doesn't cause that release.

if you wish to maintain enough carbon dioxide, put the coke into a glass and slowly add ice.

Geektastic

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#3018955 9-Jan-2023 12:47

The Coke had been in a fridge for 24 hours.

I’ll try the suggestion though! Thanks.

Paul1977

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#3019363 10-Jan-2023 00:47

Keep some drinking glasses in the fridge (the thicker the better). Pour the cold Coke into the cold glass.

timmmay

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#3019378 10-Jan-2023 07:36

Drink the coke straight from the can like the rest of us your highness! 😀 🤣

rscole86

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#3019387 10-Jan-2023 08:13

Using an insulated cup like the Huski works well too, tho they won't hold a 250ml can, so you'll need to pour the drink into it.

halper86

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#3019421 10-Jan-2023 09:27

Most restaurants and bars use a postmix system, and as @i43a2 alluded to - it is chilled as it goes through this system. You click the button on the gun and chilled filtered water comes through the line, along with carbon dioxide through another one and finally the coke syrup on another line, and they all get mixed together as it gets poured into your glass.

My recommendation would be to make sure you disturb the coke as little as possible when pouring a glass (tilt the glass like you are pouring a beer), then add ice afterwards. Compare this between adding ice before the coke to see if it makes a difference :)

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Mehrts

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#3019430 10-Jan-2023 09:58

Coke + Ice = Science!

Geektastic

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#3019432 10-Jan-2023 10:01

timmmay:
Drink the coke straight from the can like the rest of us your highness! 😀 🤣

Do you know why Continental and Asian canned drinks often come with paper or foil over the top of the can? 🥺

frankv

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#3019433 10-Jan-2023 10:01

As per 58.201 Physical & Inorganic Chemistry, gases (including CO2) are more soluble in cold water than warm, and at higher pressures. https://chempedia.info/info/solubility_of_carbon_dioxide_in_water_at_various_temperatures_and_pressures/

Coke cans are pressurised to increase the CO2 solubility and therefore fizziness of the drink. Hence the initial hiss as the can is opened, and the fact that Coke goes flat (the CO2 leaves the solution and evaporates) once a can is opened.

I suspect that what you're observing is that when you pour the Coke over ice, more of the CO2 stays in solution and therefore you see less bubbles. So the Coke is not actually flat... if you warmed it up it would create bubbles, the same as if you poured it into a room temperature glass. You should find that, in your mouth as the drink warms up from your body heat, Coke that was poured over ice feels more fizzy than un-iced Coke. Or, if you drink it down too quickly to release all the CO2 in your mouth, causes more belching.

On a similar note, however, I believe that Coke in the 2.25L bottles goes flat faster than in 1.5L bottles. So 3 day old 2.25L Coke is flatter than 3 day old 1.5L Coke.

Geektastic

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#3019434 10-Jan-2023 10:02

I’m also wondering if somehow the drinks are less carbonated than they used to be. I don’t recall this being a problem when I were a lad.

mkissin

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#3019435 10-Jan-2023 10:03

It's likely that by adding the ice you're providing a huge amount of nucleation sites for the CO2 to come out of solution, speeding the process by which that happens.

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wellygary

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#3019441 10-Jan-2023 10:08

Geektastic: I’m also wondering if somehow the drinks are less carbonated than they used to be. I don’t recall this being a problem when I were a lad.

People also tend to remember endless summers too :)....

I think it is generally accepted that we tend to always think things were better "in the good old days" :)

timmmay

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#3019457 10-Jan-2023 11:18

Geektastic:

Do you know why Continental and Asian canned drinks often come with paper or foil over the top of the can? 🥺

No - presume it's to keep them clean? You could rinse or clean them I guess.

johno1234

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#3019462 10-Jan-2023 11:25

frankv:

On a similar note, however, I believe that Coke in the 2.25L bottles goes flat faster than in 1.5L bottles. So 3 day old 2.25L Coke is flatter than 3 day old 1.5L Coke.

You mean once half the Coke is consumed? That makes sense as lower pressure and higher available volume in the bottle. My distant memory is trying to say something about partial pressure to me.

Blurtie

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#3019591 10-Jan-2023 14:52

Must be global warming in action... 😜

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