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Milk Composition
Freezing Point


Freezing point of milk: Freezing point of a solution depends on the number of particles in the solvent (water phase of milk), rather than the kind of particles. Water without solutes will freeze at zero degrees C. The presence of any solutes will depress freezing point below zero degrees C. The freezing point of milk depends upon the concentration of water-soluble components.

As milk is more diluted, the freezing point will raise closer to zero. The current official freezing point limit (-0.525 degrees Horvet or -0.505 degrees C; see Sherbon 1988 for discussion of Horvet vs Centigrade) was designed for whole-herd, bulk-tank samples or processed milk samples, and not for samples from individual cows or individual quarters. The value of -0.525 degrees Horvet is considered the upper limit which statistically is suppose to be a cut-off for most, but not absolutely all, samples to be considered "water-free" (that is, no added water).

Why would someone want to measure milk freezing point? Producers have been known to add water to their bulk tank to increase the volume of milk that they ship. They are paid in part on the total mass of milk that they ship to the processing plant. Obviously, those paying for the milk do not want to pay for added water and the freezing point of milk has ben used as a means of detecting these types of infractions.

However, freezing point of milk as a regulatory standard is really only valid for milk pooled form many cows (bulk tank milk). Many factors may affect freezing point of milk from individual cows. High producing cows might be expected to have higher freezing points than lower producing cows. Diet, and how and when the diet is fed relative to collecting the milk sample, also may affect freezing point from individual cows. Little work has been done in recent years to define freezing point on milk from modern high producing dairy cattle. [see Sherbon JW, Physical Properties of Milk, Chapter 8 in Wong et al, 1988]



Freezing Point
Milk Composition & Synthesis
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