While Jewish tradition and practice is full of food restrictions, most of them are not related to keeping Jews separate from others. Jews are commanded not to eat a host of forbidden animals, but this is in pursuit of holiness, not difference. There are, however, traditional categories that aim to separate Jews and Gentiles via the medium of food, first emerging in the Second Temple period. The ingredients may be acceptable, the utensils used to prepare them brand new, but the food is forbidden because a Gentile cooked it. What is the origin of this practice? What is its basis and what are its goals? What can we learn from its application over time?