How do I remove multiple album ratings at once?

I have over 600 albums which I've rated manually. I've decided I don't want these ratings anymore as I've found a much neater way of organising things for myself. How can I clear all of them? If I select all of the albums (with grid view) and then right click, there is no option to change the album ratings, only the normal (song?) rating, of which nothing is rated anyway (except with hollow stars that have come from the album ratings).

I hope this makes sense.