Question re: Itunes/file database

Hopefully someone can help me with this.

I have a large music library. Initially, I would rate my songs, and delete ones with low rankings. But I would delete them from Itunes ONLY, the physical file would remain in place. However, I would like to go back and actually delete the files.

Now, here is the question. Does the MP3 file itself retain my ratings info? Is it possible for me to figure out what songs I have in ITunes vs. the physical files themselves so that I can actually delete them?

Please let me know if you need additional explanation. I appreciate the help in advance. Thanks!