# Colligative property of ice cream HELP

#### Mk

Colligative property of ice cream HELP!!

How is the colligative property in effect during the manufacture of ice cream, and in the ice cream??

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#### Astronuc

Staff Emeritus
The reason is that the freezing of a liquid is affected by the presence of dissolved molecules (mainly milk proteins and sugars). This depresses the freezing point and is known as a colligative effect. The presence of the solute broadens the range of temperature that freezing will occur as well as when freezing begins. The number of solute molecules determines these effects. Consequently the amount of ice at a given temperature is sensitive to the change in solute concentration. As proteins are fairly large their colligative effect is small in comparison to that of the number of moles of sugar. Therefore, the amount of ice in an ice cream at a given temperature can be estimated by the sugar concentration.
http://www.chm.bris.ac.uk/webprojects2003/brown/thepropertiesoficecream.html

During the manufacture of ice cream one uses chilled brine (water with dissolved salt that lowers the freezing point) to get the temperature of ice cream down below the freezing point of water. Also, the freezing point of ice cream is reduced as mentioned in the quote and reference.

Colligative Property of Water Containing Rock Salt - http://www.waycross.edu/faculty/bmajdi/coligative%20properties%20of%20ice%20creaqm.htm [Broken]

Colligative Properties:Properties which depend on the number of molecules in solution, a function of concentration and molecular weight, rather than just on the total percent concentration. Such properties include boiling point elevation, freezing point depression, and osmotic concentration.
- http://www.foodsci.uoguelph.ca/dairyedu/glossary.html

http://hyperphysics.phy-astr.gsu.edu/hbase/chemical/meltpt.html
http://hyperphysics.phy-astr.gsu.edu/hbase/chemical/collig.html#c1

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#### Mk

WOW Jeez man, I can see why you added the grinning smilie at the end. :surprised. Thank you.

#### Ouabache

Homework Helper
I can vouch for the colligative properties of the brine solution with ice cream. I've been using a White Mountain hand crank freezer for over 20 yrs and I've noticed (qualitatively) the higher the proportion of rock salt to crushed ice layered between the can and the wooden bucket, the smoother the texture of the ice cream.:tongue2: Presumeably, the cream is freezing faster and therefore yields smaller ice crystals.

Now if you really want to accelerate the freezing process, you might want to try what two http://www.iastate.edu/IaStater/2001/may/icecream.html [Broken] did out in Iowa. The use liquid nitrogen in their recipe and claim it freezes almost instantaneously, giving a uniquely smoother ice cream. They are or in the process of patenting their process.

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#### Mk

I've wanted to make liquid nitrogen ice cream for two or three years. If you got one of those ice cream makers, and poured in liquid nitrogen where the ice+salt would be, would it work??

#### Ouabache

Homework Helper
Actually of the methods I've heard about, they pour the liquid nitrogen (-200 deg C) directly into the mixture that becomes ice cream. http://www.polsci.wvu.edu/Henry/Icecream/Icecream.html

I've never tried pouring liquid nitogen in replacement of the ice/salt mixture (-17 deg C). I am guessing that the wooden tub would freeze and could shatter. If the turning mechanism still functions, then you probably could freeze the ice cream that way. Let me know if you try this experiment.

Another chilling agent that is sometimes used to replace the ice/salt mixture, is dry ice (liquid $CO_2$, -78.5 deg C).

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#### Mk

Ooops I knew that. It was in popular science before too.

#### TheStatutoryApe

Ouabache said:
Actually of the methods I've heard about, they pour the liquid nitrogen (-200 deg C) directly into the mixture that becomes ice cream. http://www.polsci.wvu.edu/Henry/Icecream/Icecream.html

I've never tried pouring liquid nitogen in replacement of the ice/salt mixture (-17 deg C). I am guessing that the wooden tub would freeze and could shatter. If the turning mechanism still functions, then you probably could freeze the ice cream that way. Let me know if you try this experiment.

Another chilling agent that is sometimes used to replace the ice/salt mixture, is dry ice (liquid $CO_2$, -78.5 deg C).
So the liquid nitrogen should just evaporate off the ice cream as you mix it? I need to try this out.

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#### Ouabache

Homework Helper
TheStatutoryApe said:
So the liquid nitrogen should just evaporate off the ice cream as you mix it?
That's true.
(always take the necessary precaution's when working with liquid nitrogen and dry ice. You can get some serious frostbite:surprised ).

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