Traditionally, in order to be jewish, a person must have a jewish mother, follow the jewish religion, and abide by kosher food limitations. although they are not ironclad, these customs set "traditional" jewish people apart from others. what concept does this serve to illustrate?

The concept that the text serves to illustrate is ETHNIC BOUNDARY MAKERS which are the particular characteristics that an ethnic group has and are used to distinguish it from another ethnic group.

We can say that this is the right concept for the text because it is evident how it is describing the specific characteristics for a person to be Jewish, such as have a Jewish mother, and follow the Jewish religions among others. That being said, ethnic boundary makers can be applied to the text.

An ethnic group is a social group based on the sense of cultural tradition, shared ancestry, and common history, highlighting that group from others culturally.

When ethnic groups establish traits that set them apart from others, in Anthropology this is known as "Ethnic Boundaries".

Ethnic Boundaries are ways to create order; and Ethnic Boundary Markers are features used to state membership in an ethnic group (traits like clothing, food, language, etc.)