In the end I did not declare the loaf based on the small print on the back of the declaration form. It touches on the purpose, obviously the prevention of pests etc where said loaf could not really pose a threat. That would have been my response if asked, but definitely not in a smarta$$, amateur, lawyer manner . We were asked at customs whether we were carrying any fruit, meat etc, said, "No," and sailed through.

There were no dogs around so it was always going to be OK, anyway. The reason for asking the question in the first place was that a loaf of the proverbial had previously been sniffed out, at JFK, after loading our bags off the belt: on that occasion we were just waved on our way without even having to open the case.