An ePub is essentially a zip file. To search inside it you have to unzip it one way or another first. As far as I know Calibre doesn't handle this. There might be a plugin?
One possible trick could be to convert each cookbook to plain text an then grep for "chicken" inside the text files. Not very elegant, but it should work.
You could keep the text files in Calibre along with the original ePubs and use for instance wingrep (if you are a windows user) to search. The results should tell you which cookbooks to look in.