Kashrut: The Basics

Kosher is not a kind of food. It is a system of laws governing what may be eaten, how it must be prepared, and what may be combined.

By The Editors

The Fundamentals · 3 minute read

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Summary. Kashrut is the body of Jewish dietary law that governs which animals may be eaten (Vayikra 11, Devarim 14), how those animals must be slaughtered (shechita), what part of the animal may not be eaten (cheilev, blood, the sciatic nerve), and the strict separation of meat and dairy (derived from Shemot 23:19, repeated in Shemot 34:26 and Devarim 14:21: lo tevashel g’di b’chalev imo). The principal categories are basar (meat), chalav (dairy), and parve (neither). Reliable supervision (hashgacha) confirms compliance.

Permitted and Forbidden Animals

Land animals: split hoof and chew the cud (cow, sheep, goat, deer — kosher; pig, camel, hare — not). Water creatures: fins and scales (most fish kosher; shellfish, eel, catfish — not). Birds: the Torah lists 24 forbidden species (Vayikra 11:13–19); the tradition restricts birds to those with a continuous mesorah (received tradition) of kashrut — chicken, turkey, duck, goose are normative; quail, dove, pigeon are kosher. Insects: forbidden, with the exception of certain locust species in some Yemenite traditions.

Shechita

Permitted mammals and birds must be slaughtered by shechita — a single swift cut across the throat by a trained shochet using a perfectly smooth blade. The procedure is designed to render the animal unconscious instantly and to drain the blood. The animal must then be inspected (bedikat haPnimiyut) for signs of disease. Glatt kosher (Yiddish for “smooth”) refers to lungs free of any adhesions, the strictest standard.

Meat and Dairy

The Torah’s thrice-repeated lo tevashel g’di b’chalev imo (“do not cook a kid in its mother’s milk”) is the basis for a sweeping Halachic separation of meat and dairy. Jews maintain separate dishes, separate utensils, separate cooking equipment, and a waiting period between eating meat and eating dairy (the waiting period varies: 3 hours is common Dutch and German practice; 6 hours is the Eastern European and Sephardic standard; 1 hour is the Western European Dutch minority). The reverse — dairy to meat — generally requires only rinsing the mouth and eating something parve, except in the case of hard cheese.

Parve

Parve foods are neither meat nor dairy: fish (which is also subject to a Talmudic stricture against eating with meat at the same table, per the Beit Yosef on Yoreh De’ah 116), eggs, fruits, vegetables, grains, oils, and most processed foods made entirely of plant ingredients. Parve foods may be eaten with either meat or dairy. Bishul akum (food cooked entirely by a non-Jew) is a separate Halachic category that some communities are stricter about than others.

Hashgacha

Reliable supervision (hashgacha) by a recognized kashrut agency is what allows processed and packaged foods to be marked kosher. The major American agencies include the OU (Orthodox Union), OK Kosher, Star-K, Kof-K, and Chof-K. Each has its own standard mark. International agencies include the London Beth Din, Badatz (Jerusalem), and the Manchester Beth Din. The agency’s mark on a package indicates the agency stands behind that product as kosher.

Where Denominations Diverge

Orthodox observe full kashrut, including separate kitchens and supervised processed foods. Conservative observance varies widely; Conservative kashrut at home is common, and the movement’s Magen Tzedek certification adds ethical standards beyond traditional kashrut. Reform Judaism does not require kashrut but increasingly affirms it as an ethical and identitarian practice; Reform kashrut may emphasize vegetarianism, avoiding factory-farmed meat, or eco-kashrut. Reconstructionist often follows similar lines. Sephardic kashrut is largely identical to Ashkenazi with minor variations (acceptance of glatt is less universal; treatment of legumes on Pesach differs).

Sources

Torah: Vayikra 11; Devarim 14; Shemot 23:19, 34:26; Devarim 14:21.

Mishnah Chullin; Talmud Bavli, Chullin (entire tractate).

Shulchan Aruch, Yoreh De’ah 1–127.

Rabbi Yosef Karo and Rema, Shulchan Aruch on Basar B’Chalav.