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Why do we salt the ice when making ice cream?

timothyrice.org

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Re: Why do we salt the ice when making ice cream?

#11

Post by ljf »

timrice wrote: post #3
majikandy wrote: post #2

Always heard about this but never tried it. Sounds like fun. Great description, very clear and much better than just saying it lowers the temperature! Nice writing.

Author here, thank you! It's been bouncing around in the back of my brain for a long time. I couldn't find any clear and concise explanations about what really happens when salt is added to ice, so I did some research and wrote it out myself :D

Thanks for this - I was watching a video of ice cream making with my son the other day, and the guy making the ice-cream said how it lowered the temp, and I totally didn't believe it was correct and started to explain my theory before realising I had no idea. Great to see it laid out so clearly!

Re: Why do we salt the ice when making ice cream?

#12

Post by majikandy »

lesuorac wrote: post #8

I thought it was going to about adding salt to the ice cream but was not :/ I have a compressor so I have no use of a salted ice bath but I find that using salt in the mixture will make the ice cream not as hard when left overnight or longer in the freezer.

A bit of alcohol would achieve that too right? Eg rum&raisin ice cream

Re: Why do we salt the ice when making ice cream?

#14

Post by iamkroot »

lend000 wrote: post #6

> It turns out, yes! What happens is that when the salt is added some of the ice melts – pulling heat from the system – until the temperature has reached the new, lower equilibrium point. Correction, or addendum here: the actual dissolution of the salt is an endothermic process, so even if there was no ice, the temperature of water decreases when salt is dissolved.

Author here.

Hah, that's true, but I didn't want to mention it as it's not entirely in the aim of the essay :)

Re: Why do we salt the ice when making ice cream?

#15

Post by zwieback »

majikandy wrote: post #12
lesuorac wrote: post #8

I thought it was going to about adding salt to the ice cream but was not :/ I have a compressor so I have no use of a salted ice bath but I find that using salt in the mixture will make the ice cream not as hard when left overnight or longer in the freezer.

A bit of alcohol would achieve that too right? Eg rum&raisin ice cream

Right, alcohol, sugar and salt all change the hardness of the ice cream but you can only add so much until the flavor isn't what you want anymore. I don't think the ice cream texture is due to the melting point, though, that the post talks about, it's also whether large enough ice crystals can form.

It feels like cheating but adding stabilizers (gums, mostly) was really a game changer for our homemade ice cream.

Re: Why do we salt the ice when making ice cream?

#16

Post by iamkroot »

majikandy wrote: post #12
lesuorac wrote: post #8

I thought it was going to about adding salt to the ice cream but was not :/ I have a compressor so I have no use of a salted ice bath but I find that using salt in the mixture will make the ice cream not as hard when left overnight or longer in the freezer.

A bit of alcohol would achieve that too right? Eg rum&raisin ice cream

OP author here.

Yes, though you have to be careful. If you add too much alcohol you'll prevent your mixture from properly freezing.

David Leibowitz, author of "The Perfect Scoop" recommends no more than 45ml of 80 proof liquor per 1 liter of ice cream mixture.

Re: Why do we salt the ice when making ice cream?

#17

Post by lapetitejort »

lesuorac wrote: post #10
majikandy wrote: post #7

Earlier quoted context omitted.

More importantly, how was the ice cream you made? Apparently liquid nitrogen ice cream makes smaller crystals or something and tastes better? That could be the sequel…

> Apparently liquid nitrogen ice cream makes smaller crystals or something and tastes better? It's about how fast you freeze the ice cream so the crystals don't grow. -- You can get N2 from a local gas supplier but a lot of grocery stores stock CO2 (Dry Ice) that can also be used for ice cream. CO2 has the disadvantage of if you get it in the ice cream it makes it carbonated but the smoke looks like a witches cauldro…

My favorite use of dry ice is making Boo Bubbles:

1. Create a mixture of soap, water, and glycerin. This will make bubbles harder to pop.

2. Get a sealable container, poke a hole in the lid, the glue a tube in the hole.

3. Fill the container with water, then drop in pieces of dry ice. The CO2 should escape through the tube.

4. Stick the other end of the tube into the soap mixture.

5. Large bubbles will form with a cloudy gas of CO2.

6. Use towels to carry the bubbles, throw in the air, and combine with other bubbles.

I do this every Halloween. Kids get a kick out of it. A lucky few will stick around and learn about CO2, tensile strength, etc.

Re: Why do we salt the ice when making ice cream?

#18

Post by an1sotropy »

lend000 wrote: post #6

> It turns out, yes! What happens is that when the salt is added some of the ice melts – pulling heat from the system – until the temperature has reached the new, lower equilibrium point. Correction, or addendum here: the actual dissolution of the salt is an endothermic process, so even if there was no ice, the temperature of water decreases when salt is dissolved.

But which has a greater effect on removing heat from the cream-containing vessel: the decrease in temperature from the dissolution of salt, or the more efficient thermal coupling to the vessel provided by the salt/ice slurry (versus the original solid ice chunks)?

The goal is to remove heat from the cream faster than the system as a whole warms up due to room temperature. I thought the value of salt was to help the cream win that race by making a better heat sink.

Re: Why do we salt the ice when making ice cream?

#19

Post by majikandy »

zwieback wrote: post #15
majikandy wrote: post #12

Earlier quoted context omitted.

A bit of alcohol would achieve that too right? Eg rum&raisin ice cream

Right, alcohol, sugar and salt all change the hardness of the ice cream but you can only add so much until the flavor isn't what you want anymore. I don't think the ice cream texture is due to the melting point, though, that the post talks about, it's also whether large enough ice crystals can form. It feels like cheating but adding stabilizers (gums, mostly) was really a game changer for our homemade ice cream.

Yep I hear that, but also a frappucino without Xanthan gum is just a floaty slushy mess on sugary water.

Re: Why do we salt the ice when making ice cream?

#20

Post by iamkroot »

majikandy wrote: post #7
timrice wrote: post #3

Earlier quoted context omitted.

Author here, thank you! It's been bouncing around in the back of my brain for a long time. I couldn't find any clear and concise explanations about what really happens when salt is added to ice, so I did some research and wrote it out myself :D

More importantly, how was the ice cream you made? Apparently liquid nitrogen ice cream makes smaller crystals or something and tastes better? That could be the sequel…

Delicious, of course!

And yes, the other commenter is correct. LNO2 works so well because it freezes the ice cream so fast that the crystals don't have time to grow very large, which produces a nice and smooth texture in the final product.

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