Freezing Point of Milk

Most recent answer: 10/22/2007

what is the melting point for milk
- Anonymous
This is a great question!

The exact freezing point of milk (also called the melting point) varies slightly according to the individual cow, the breed, the time of day / season that the milk is collected, the type of feed that the cow receives, etc. According to , the majority of cows produce milk with a natural freezing point of -0.5250 to -0.5650 °C, with an average of about -0.5400 C. When you think about all those factors I just listed, tho, this may seem like a surprisingly narrow range. And it is remarkably narrow. The reason is this...

Milk is produced by a part of the cow called the mammary gland. (All mammalian species use mammary glands to produce milk.) One of the ways that the mammary gland works is to produce milk with the same overall "osmotic pressure" as the animal’s blood has.* Osmotic pressure is basically a measure of how much stuff is dissolved in a liquid, which determines the liquid’s freezing point. Because of the important role of blood in the body, the body works very hard to keep its osmotic pressure at an ideal level, and that doesn’t vary much from animal to animal - all cows have basically the same physiological requirements for their blood.

An interesting way that the freezing point of milk is used is to determine if milk is watered down - either intentionally by the producer or naturally as a result of the cow being unhealthy. The freezing point of pure water is exactly 0 °C. The more stuff you dissolve in the water, the lower the freezing point gets - this is called Freezing Point Depression. Milk that has been watered down contains more water and less solutes, so its freezing point is closer to 0 °C. Most milk processors will conclude that milk has been watered down if the freezing point is anywhere above -0.250 °C.


* Water flows naturally to establish equilibrium of osmotic pressure. That means that if two chambers are connected so that water can flow between them but solutes can’t, the water will naturally move so the osmotic pressure is the same on both sides. In a mammal, the blood vessels and the mammary glands are the two chambers - water can flow back and forth between them, but (most of) the stuff dissolved in the blood/milk can not. The water in milk comes directly from the cow’s blood.

(published on 10/22/2007)

Follow-Up #1: melting milk

Interesting response, thank you! I was wondering though, do the ingredients of milk melt at the same rate? Ie. even though milk is a solution of sugars and fats and water (and other stuff), do some parts, like the fat/cream for example, begin to melt earlier? In the same way drinking from the bottom of an ice slushy will leave you with a hunk of unflavoured ice after a bit, would you get a 'creamier' milk forming at the bottom of your container while everything else is still in the process of unfreezing?Thanks!
- Shaun (age 35)
JHB, GA, South Africa

Milk will be very similar to the slushy. The ice that forms is almost pure water, leaving the sugars, salts, and fats behind. You could make condensed milk by removing the ice crystals. My great grandfather used to make condensed liquor by removing ice crystals from it.

Mike W.

(published on 04/01/2020)

Follow-up on this answer