Keeping Kosher

Kashrut is a system of separations rather than a list of banned foods, and the separations do most of the work.

Permitted land animals must both chew the cud and have cloven hooves. Permitted sea creatures must have fins and scales, which excludes every shellfish. Birds are permitted by inherited tradition rather than by a stated rule, so the list is received rather than derived, and novel species raise real questions. Blood is prohibited absolutely, which requires meat to be drained and salted before use.

The separation of meat from dairy is a rabbinic elaboration of a single verse forbidding the boiling of a kid in its mother's milk, and it is the rule that shapes a kitchen. A kosher household maintains two sets of crockery, cutlery and pots, frequently two sinks and two dishwashers, and observes a waiting period of between one and six hours after meat before dairy may be eaten, the interval varying by community and inherited from parents. Anything neither meat nor dairy is neutral and may accompany either, which is why fish and eggs occupy a category of their own.

Passover adds a second system on top of the first. Leaven is not merely avoided but must be absent from the property, so the kitchen is cleaned, remaining leaven is formally sold to a non-Jew for the duration, and a further set of dishes is used.

The reasons given have varied enormously. Hygiene explanations are popular, modern, and unsupported by the texts, which mostly give holiness and separation as the reason and decline to explain further. Maimonides offered health arguments. Other authorities insisted the laws are decrees whose whole point is obedience precisely because no reason is supplied.

Kosher supervision is a substantial industry and an unusual instance of religious law operating inside modern food manufacturing.

Certification is issued by agencies that inspect ingredients, equipment and process, and their symbols appear on a very large share of packaged food in the United States. The difficulty is industrial rather than culinary: emulsifiers, enzymes, gelatine, flavourings and processing aids all require tracing to source, and a line used for dairy production cannot simply be switched to meat. The certification market is competitive, agencies differ in stringency, and consumers who are not Jewish, Muslims, vegetarians and people managing allergies, make up a large part of the demand.

Shechita, the method of slaughter, is where kashrut meets the law of the state. It requires a single continuous cut across the throat with an exceptionally sharp blade free of any nick, performed by a trained and licensed slaughterer, and the animal must not be stunned beforehand, because the law requires it to be healthy and intact at the moment of slaughter. Islamic dhabihah is similar in principle, and in several countries the two are regulated together.

A number of European countries now ban slaughter without prior stunning on animal welfare grounds, among them Sweden, Norway, Switzerland, Denmark and Slovenia, along with the Belgian regions of Flanders and Wallonia, whose bans were upheld by the Court of Justice of the European Union in 2020. Jewish and Muslim organisations oppose these as restrictions on religious practice, and point out that some historical versions of such laws were not primarily about animals at all. Veterinary opinion on whether the method causes greater suffering is divided rather than settled. Both of those statements are true and both belong in any honest account.