What makes mozzarella cheese so stretchy?
Milk contains proteins consisting of coiled-up chains of molecules. When you make cheese, these proteins are separated out during the curdling of the milk, to make curds. In the manufacture of mozzarella, the curds are then put into hot, salty water. This uncoils the proteins and turns them into long strands, which are then repeatedly compressed and stretched. This forces the strands to line up, creating the famous stringy consistency.