So my American and British readers can get the joke, I'd better say ahead of the story that "New World" is a local supermarket chain.
It seems a writer told him about a recent experience with a Certain Major Publisher. In a chapter on Roman food, i.e. from Rome 2000 years ago, she wrote that they couldn’t use ingredients from the new world such as tomatoes, potatoes and corn (the Americas not having been discovered by the Romans). The editor corrected this to “from New World”.
The author changed it back to “from the new world” on the page proofs.
The editor corrected this again to “from New World”.
So the editor changed it to “from the supermarket”.