Why does Toni Morrison seem to refer to food so much in Recitatif?

This depends on the context of food. A grocery store, especially a high-end one, symbolizes abundance. The fact that the two women meet here in their second encounter is telling, for both of them have come a long way from their straitened childhood. They are both married and have money, though Roberta has quite a bit more. They have come a long way since St. Bonny's, and though there are numerous complications in their relationship with each other, they are on a different playing field now.