蛋白 = egg white 蛋黄 = egg yolk

I don't know Chinese so I will rely on Domasla's expertise for the translation. Another way these words are written sometimes is 'the white of an egg' 'the yolk of an egg' This is used in a recipe when telling how many eggs to use "the yolk of three eggs' 'the white of two eggs' But the other way also gives you the option of using the word as a collective noun, like water, which is not measured. 'I got egg yolk on my hands' 'we brushed the cookies with egg white'