Kosher foods are foods that conform to the Jewish dietary regulations of kashrut (dietary law). The laws of kashrut apply to food derived from living creatures and kosher foods are restricted to certain types of mammals, birds and fish meeting specific criteria; the flesh of any animals that do not meet these criteria is forbidden by the dietary laws. Furthermore, kosher mammals and birds must be slaughtered according to a process known as and their blood may never be consumed and must be removed from the meat by a process of salting and soaking in water for the meat to be permissible for use. All plant-based products, including fruits, vegetables, grains, herbs and spices, are intrinsically kosher, although certain produce grown in the Land of Israel is subjected to other requirements, such as tithing, before it may be consumed.
Kosher food also distinguishes between meat and dairy products. Meat products are those that comprise or contain kosher meat, such as beef, lamb or venison, kosher poultry such as chicken, goose, duck or turkey, or derivatives of meat, such as animal gelatin; non-animal products that are processed on equipment used for meat or meat-derived products are also considered to belong to this category. Dairy products are those which contain milk or any derivatives such as butter or cheese; non-dairy products that are processed on equipment used for milk or milk-derived products are also considered as belonging to this category. Because of this categorization, meat and milk or their respective derivatives are not combined in kosher foods, and separate equipment for the storage and preparation of meat-based and dairy-based foods is used in order for food to be considered kosher.
Another category of kosher food, called contains neither meat, milk nor their derivatives; they include foods such as fish, eggs from permitted birds, produce, grains, fruit and other edible plants. They remain pareve if they are not mixed with or processed using equipment that is used for any meat or dairy products.
Because of the complexities of modern food manufacturing, kashrut agencies supervise or inspect the production of kosher foods and provide a certification called a hechsher to verify for kosher food consumers that it has been produced in accordance with Jewish law.
Jewish dietary law is primarily derived from Leviticus 11 and Deuteronomy 14:1-21. Foods that may be consumed according to Jewish religious law are termed kosher () in English, from the Ashkenazi pronunciation of the Hebrew term kashér (), meaning "fit" (in this context, fit for consumption). Foods that are not in accordance with Jewish law are called treif (; , derived from trāfáh) meaning "torn."
Permitted and forbidden animals
The Torah permits eating only those land animals that chew their cud and have cloven hooves. Four animals, the hare, hyrax, camel, and pig, are specifically identified as being forbidden because they possess only one of the above characteristics: the hare, hyrax and camel are hindgut fermenters and chew their cud but do not have cloven hooves, while the pig has a cloven hoof but does not chew its cud.
The Torah lists winged creatures that may not be consumed, mainly birds of prey, fish-eating water-birds, and bats. Certain domesticated fowl can be eaten, such as chicken, geese, quail, dove, and turkey.
The Torah permits only those fish which have both fins and scales to be eaten. Monkfish is not considered kosher. To comply with kosher requirements, a fish must have fins and easily detached scales; the scales of a sturgeon are extremely hard to remove, hence it is non-kosher. Other seafood considered non-kosher includes shellfish like clams, oysters, crabs and shrimp. There is also a risk of products like seaweed and kelp being contaminated by microscopic, non-kosher crustaceans.
The Torah forbids two types of (creeping things): Earth crawlers, e.g. mouse, lizard Flying creeping things, with four exceptions: Two types of locust, the cricket, and the grasshopper (translations of the species names vary).
Animal products
In addition to meat, products of forbidden species and from unhealthy animals were banned by the Talmudic writers. This included eggs (including fish roe), as well as derived products such as jelly, but did not include materials merely "manufactured" or "gathered" by animals, such as honey (although, in the case of honey from animals other than bees, there was a difference of opinion among the ancient writers).