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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?

#41

Post by topaz0 »

Taniwha wrote: post #27

Surely part of the issue is that the ice at If you add ice you reduce the equilibrium temp and as a result the < 0C ice temp can be passed to the liquid phase and as a result on to the inner con tain er where you're making the ice cream

This effect should be negligible. The whole point here is that it takes way more energy to take a chunk of ice and turn it into water (at fixed temp -- namely the freezing point) than it does to heat that chunk of ice a few degrees (below the freezing point). And remember that you don't just have to cool the cream to its freezing point, you also have to remove enough energy to overcome its latent heat of fusion. If you were doing this just with the heat capacity of ice from like -20 to -5 C, you would need many times more ice than you could make ice cream. Like tens to hundreds of times. The blog discusses some related facts a bit near the end.

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

#42

Post by annoyingnoob »

floren wrote: post #35
foobarian wrote: post #33

Earlier quoted context omitted.

This was a bit hard to spot in the writeup, as I have no clue about how ice cream making and machines work. Otherwise we could just use ice, which will be as cold as the refrigerator can get it. (I doubt the endothermic reaction of dissolving the salt contributes very much to the cooling). Now that I think about it, if I were doing this I would use antifreeze for the coolant instead of wasting salt. Bonus, I can stor…

Salt's way cheaper than antifreeze, and I'd be a lot happier about getting a little stray salt in my ice cream than getting a little stray ethylene glycol (with bittering agents, since 2010).

You could use propylene glycol that is Generally Recognized As Safe.

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

#44

Post by alliao »

foobarian wrote: post #33
Taniwha wrote: post #27

Surely part of the issue is that the ice at If you add ice you reduce the equilibrium temp and as a result the < 0C ice temp can be passed to the liquid phase and as a result on to the inner con tain er where you're making the ice cream

This was a bit hard to spot in the writeup, as I have no clue about how ice cream making and machines work. Otherwise we could just use ice, which will be as cold as the refrigerator can get it. (I doubt the endothermic reaction of dissolving the salt contributes very much to the cooling). Now that I think about it, if I were doing this I would use antifreeze for the coolant instead of wasting salt. Bonus, I can stor…

antifreeze is really really really toxic for mammals so there's that, while ingesting bit of salt never hurt anyone.. maybe diabetics

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

#45

Post by ndiddy »

OJFord wrote: post #43

Alternatively (edit - in the product itself): because it's delicious. If you like 'salted caramel' ice cream, try sprinkling some salt on vanilla ice cream. (I bet you'll find it's the 'salted' you like more than the 'caramel'.)

Do you happen to know if MSG also works? I’m a big MSG fan, I would try this myself but I don’t have any vanilla ice cream at the moment

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

#46

Post by Taniwha »

iamkroot wrote: post #38
Taniwha wrote: post #27

Surely part of the issue is that the ice at If you add ice you reduce the equilibrium temp and as a result the < 0C ice temp can be passed to the liquid phase and as a result on to the inner con tain er where you're making the ice cream

The ice actually comes up to the temperature of the water while it's melting. That's what the equilibrium temperature is: the temperature of the entire ice / water system until it's been converted to all liquid or all solid. Naturally there's some small local variations, but if you let the system come up to steady state, that's what will occur.

That's true of the surface of the ice, but the core is colder

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

#47

Post by dmd »

OJFord wrote: post #43

Alternatively (edit - in the product itself): because it's delicious. If you like 'salted caramel' ice cream, try sprinkling some salt on vanilla ice cream. (I bet you'll find it's the 'salted' you like more than the 'caramel'.)

The salt being discussed here does not end up in the ice cream.

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

#48

Post by Taniwha »

fsckboy wrote: post #31
Taniwha wrote: post #27

Surely part of the issue is that the ice at If you add ice you reduce the equilibrium temp and as a result the < 0C ice temp can be passed to the liquid phase and as a result on to the inner con tain er where you're making the ice cream

it's not just the coldness of the ice, salt dissolving in water actually decreases the temperature, it's an endothermic reaction. the salt dissolving into the water brings the water down to 0... omg time for Farenheit to shine... brings the water down to 0F without freezing it (because of the lower equilibrium temp), which is -17.8C (Farenheit uses this endothermic salted water temp as its definition of 0, I think be…

That's why I said it was "part of the issue" - but once the salt has dissolved the system is kept at -5 for a period of time because inside of the ice cubes are < 5C

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

#49

Post by distortedsignal »

OJFord wrote: post #43

Alternatively (edit - in the product itself): because it's delicious. If you like 'salted caramel' ice cream, try sprinkling some salt on vanilla ice cream. (I bet you'll find it's the 'salted' you like more than the 'caramel'.)

The article is specifically talking about salting the ice in a homemade ice cream maker like this[0]. The ice is used to reduce the temperature of the milk/sugar/etc. to "freeze" the ice cream. None of this salt gets into the ice cream.

I agree with you - people should try salting their ice cream. But the article is about a different part of the ice cream making process.

[0] https://www.amazon.com/Nostalgia-WICM4L-Electric-4-Quarts-Mi...

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

#50

Post by iamkroot »

Taniwha wrote: post #46
iamkroot wrote: post #38

Earlier quoted context omitted.

The ice actually comes up to the temperature of the water while it's melting. That's what the equilibrium temperature is: the temperature of the entire ice / water system until it's been converted to all liquid or all solid. Naturally there's some small local variations, but if you let the system come up to steady state, that's what will occur.

That's true of the surface of the ice, but the core is colder

For a little while, yes. Ice has middling thermal conductivity, it'll eventually homogenously warm to the melting point.
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