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Earlier quoted context omitted.
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.
Earlier quoted context omitted.
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.
Earlier quoted context omitted.
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.
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
1. To make ice cream, we need to cool milk/cream below the freezing point of water (because milk/cream contains water).
2. To cool things, liquids have good thermal conductivity properties, so we would prefer to use a liquid.
3. We need some substance which is still a liquid at slightly below freezing.
4. It happens that salted water has this property and is relatively cheap.
https://www.mt.com/us/en/home/applications/Application_Brows...
Some companies leverage this effect to make non-reversible temperature indicators that change color at specific temperatures.
> 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.
That's technically true, but it's a rather negligible amount.
Salt has an enthalpy of dissolution of +3.9kJ/mol (1) and a molar mass of 58.44g/mol (2), for roughly 67J/g.
For comparison, water=ice has an enthalpy of fusion of 334J/g (3), and you'll be adding at least three times more ice than salt (as max salt concentration is around 25% g/g (4) ). When you take this into account, it's a whole order of magnitude of difference, so for practical purposes you can outright ignore the heat being consumed by the dissolution of the salt.
Sources:
1. https://chem.libretexts.org/Bookshelves/Physical_and_Theoret...
2. https://en.wikipedia.org/wiki/Sodium_chloride
> 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 c…
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.