Question

When you heat milk and leave it, what is the film that forms at the top made of?

Answer 1

I believe that occurs when milk proteins (called caseins) coagulate; allow me a second to refresh my memory...

Answer 2

" When milk is heated up, some of the water in it evaporates, leaving behind a higher concentration of solid proteins and fat molecules. These proteins, casein and beta, clump together when the liquid reaches a temperature of around 113 to 122° Fahrenheit (45 to 50° Celsius). As the heating continues, the soft protein layer begins to dry out, forming a skin on the surface. "

Take a look here: http://www.wisegeek.com/why-does-milk-form-a-skin-when-it-is-heated.htm

Hope this helps!

Answer 3

^ that stuff always grossed me out.*pukes*