# MILK SKIN

**URL:** <https://boards.straightdope.com/t/milk-skin/36829>\
**Category:** Factual Questions\
**Created:** [October 13, 2000, 7:46pm UTC](https://boards.straightdope.com/t/milk-skin/36829 "2000-10-13T19:46:37Z")\
**Posts on this page:** 5\
**Page:** 1

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**Author:** ![msbrown](https://avatars.discourse-cdn.com/v4/letter/m/8e7dd6/32.png) [@msbrown](https://boards.straightdope.com/u/msbrown)\
**Post date:** [October 13, 2000, 7:46pm UTC](https://boards.straightdope.com/t/milk-skin/36829/1 "2000-10-13T19:46:37Z")

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Why does heated milk develope a ‘skin’ once it starts to cool?

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**Author:** ![LisaRx](https://avatars.discourse-cdn.com/v4/letter/l/77aa72/32.png) [@LisaRx](https://boards.straightdope.com/u/LisaRx)\
**Post date:** [October 13, 2000, 8:31pm UTC](https://boards.straightdope.com/t/milk-skin/36829/2 "2000-10-13T20:31:40Z")

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This is a guess, but I think it has to do with breaking down the structures of the proteins contained in it.

Sort of like when you cook an egg, it becomes hard and opaque, maybe?

Someone else will probably give a more exact answer shortly!

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**Author:** ![sailor](https://avatars.discourse-cdn.com/v4/letter/s/a587f6/32.png) [@sailor](https://boards.straightdope.com/u/sailor)\
**Post date:** [October 13, 2000, 8:37pm UTC](https://boards.straightdope.com/t/milk-skin/36829/3 "2000-10-13T20:37:52Z")

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yup, the proteins coagulate with heat.

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**Author:** ![funneefarmer](https://avatars.discourse-cdn.com/v4/letter/f/9fc348/32.png) [@funneefarmer](https://boards.straightdope.com/u/funneefarmer)\
**Post date:** [October 13, 2000, 10:01pm UTC](https://boards.straightdope.com/t/milk-skin/36829/4 "2000-10-13T22:01:29Z")

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From [Mad Scientist Network](http://www.madsci.org/posts/archives/dec96/843221952.Ch.r.html)

“Milk is a colloidal mixture of water, lipids, carbohydrates and proteins. When you heat this mixture, evaporation goes on and the upper layer of milk gets supersaturated, high temperature denatures milk proteins and the colloid collapses. The “film” hence is a layer of clotted proteins and long chain carbohydrates, interpenetrated and fused by milk fats. (Consider the fact that almost all proteins have hydrophobic inner core which in normal state is not exposed to the solvent. When protein denatures, the hydrophobic core gets exposed and fats penetrate it, completing the process of “film” formation).”

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**Author:** ![tomndebb](https://avatars.discourse-cdn.com/v4/letter/t/b9e5f3/32.png) [@tomndebb](https://boards.straightdope.com/u/tomndebb)\
**Post date:** [October 14, 2000, 4:06am UTC](https://boards.straightdope.com/t/milk-skin/36829/5 "2000-10-14T04:06:59Z")

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So the skim on heated milk is milk suffering rabies?