milk whey vs blood serum

milk whey and blood serum both are nouns.

Word	Noun	Adjective	Verb	Adverb
milk whey	Yes	No	No	No
blood serum	Yes	No	No	No

As nouns, blood serum is a hypernym of milk whey; that is, blood serum is a word with a broader meaning than milk whey:

milk whey: the serum or watery part of milk that is separated from the curd in making cheese
blood serum: an amber, watery fluid, rich in proteins, that separates out when blood coagulates

Other hypernyms of milk whey include serum.

milk whey (noun)	blood serum (noun)
the serum or watery part of milk that is separated from the curd in making cheese	an amber, watery fluid, rich in proteins, that separates out when blood coagulates