kosher

Conforming to religious law with regard to the preparation and consumption of food; in Judaism, conforming to the food laws (kashrut) of the Torah (as laid down in Deuteronomy and Leviticus) and the Mishnah. Forbidden food is called trefah. For example, only animals that chew the cud and have cloven (split) hooves may be eaten; cows and sheep are kosher, pigs are trefah. There are rules (shechitah) governing their humane slaughter and their preparation (such as complete draining of blood), which also apply to fowl. Only fish with scales and fins may be eaten; not shellfish. Birds listed in Leviticus may not be eaten. Milk products may not be cooked or eaten with meat or poultry, or until four hours after eating them. Utensils for meat must be kept separate from those for milk.

The injunction against eating milk products and meat together stems from Exodus 23:19, which states that ‘you must not cook a kid (young goat) in its mother's milk’. Food that contains neither meat nor milk products can be eaten with either, and is called parev; these include vegetables, eggs, and wine.

In practice, Orthodox Jews have separate kitchen areas, washing-up equipment, crockery, cutlery, and saucepans for the two kinds of food, dairy and meat. There is a wait of several hours after a meal with meat before milk products can be eaten. When meat is bought from a kosher butcher, the purchaser must cover it with water for 30 minutes and then with salt for an hour.

Kosher food producers, kosher shops, butchers, and restaurants must have a licence from the Beth Din (a rabbinic board), which will be displayed on their premises and products. This guarantees that food manufacture has been supervised by rabbis and is properly kosher, including preparation and any hidden additives.

There have been various explanations for the origins of these laws, particularly hygiene: pork and shellfish spoil quickly in a hot climate. Many Reform Jews no longer feel obliged to observe these laws.