פירוש על עבודה זרה 74:17

The problem is that even flour ground by non-Jews is permitted.

The final conclusion is that the food must have been changed by fire for it to be prohibited. The role of fire in creating civilization is something that both evolutionary biologists and anthropologists have noted. It is likely that one of the major shifts in primate evolution occurred when human beings (homo something or other) learned to cook their meat. This allowed them to digest far more calories, which allowed their brains to grow and for them to evolve in very different directions from other primates. No other animal has the ability to manipulate fire and most animals fear fire (think of Shere Khan from Jungle Book). Thus manipulation of fire is quintessentially human. Once food has been cooked by fire it is out of the animal realm and in the civilized realm.