What part of speech is took in the sentence The dog ate his food before you it?

The word "took" is missing from the sentence you provided.

Here's a breakdown of the sentence:

* The dog ate his food before you it.

This sentence is grammatically incorrect. Here's a possible correction:

* The dog ate his food before you took it.

In this corrected sentence, "took" is a verb. Specifically, it's the past tense of the verb "take."