奶皮

nǎi shang jié le yī céng nǎi pí

奶上结了一层奶皮。

A skin had formed on the top of the milk.

wǒ yòng xì shāi guò lǜ niú nǎi shang de nǎi pí

我用细筛过滤牛奶上的奶皮。

I sift the milk to remove the milk skin.