Kosher foods
Kosher foods are foods that conform to the Jewish dietary regulations of kashrut. 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". Foods that are not in accordance with Jewish law are called treif 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 detachable 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 risk of products like seaweed and kelp being contaminated by microscopic, non-kosher crustaceans.
The Torah forbids two types of :
- Earth crawlers, e.g. mouse, lizard
- Flying creeping things, with four exceptions: Two types of locust, the cricket, and the grasshopper.
Animal products
According to the rabbinical writers, eggs from ritually pure animals would always be prolate at one end and oblate at the other, helping to reduce uncertainty about whether consumption was permitted or not.
Dairy products
The classic rabbinical writers imply that milk from an animal whose meat is kosher is also kosher. As animals are considered non-kosher if they are discovered to have been diseased after being slaughtered, this could make their milk retroactively non-kosher.By adhering to the principle that the majority case overrules the exception, Jewish tradition continues to regard such milk as kosher, since statistically it is true that most animals producing such milk are kosher; the same principle is not applied to the possibility of consuming meat from an animal that has not been checked for disease.
Hershel Schachter said that with modern dairy-farm equipment, milk from the minority of non-kosher cows is invariably mixed with that of the majority of kosher cows, thus invalidating the permissibility of consuming milk from a large dairy operation. Many leading rabbis rule milk permissible, as do major kashrut authorities.
Human breast milk
Breast milk from a woman is permitted. Authorities assert breast milk may be consumed directly from the breasts only by children younger than four, and children older than two were only permitted to continue to suckle if they had not stopped doing so for more than three consecutive days.Cheese
The situation of cheese is complicated as hard cheese often involves rennet, an enzyme that splits milk into curds and whey.Many forms of rennet are derived from the stomach linings of animals, but since the 1990s rennet is often made recombinantly in microbes because it can be produced more efficiently.
Because the rennet could be derived from animals, it could potentially be non-kosher. Rennet made recombinantly, or from the stomachs of kosher animals, if they have been slaughtered according to the laws of kashrut, can be kosher. Cheese made from plant-derived rennet can also be kosher. Many authorities require that the cheese-making process follow certain stringencies to be kosher.
According to the Shulchan Aruch, a rabbinic decree prohibits all cheese made by non-Jews without Jewish supervision, even if its ingredients are all kosher, because very frequently the rennet in cheese is not kosher. Rabbeinu Tam and some of the geonim suggested that this decree does not apply in a location where cheese is commonly made with only kosher ingredients, a position that was practiced in communities in Narbonne and Italy.
Many contemporary Orthodox authorities do not follow this ruling, and hold that cheese requires formal kashrut certification to be kosher; some even argue this is necessary for cheese made with non-animal rennet. However, some such as Joseph B. Soloveitchik ate generic cheeses without certification. Isaac Klein's tshuva authorized the use of cheese made from non-kosher rennet, and this is widely practised by observant Conservative Jews and Conservative institutions.
Eggs
The eggs of kosher birds are kosher. Eggs are considered pareve despite being an animal product.Blood found in eggs
Occasionally blood spots are found within an egg, which can affect the kosher status of the egg. The halacha varies depending on whether or not there is a possibility of the egg being fertilized.If the egg may have been fertilized, the Rishonim and Shulchan Aruch suggest a complex set of rules for determining whether the egg may be eaten; among these rules, if blood appears on the yolk, the entire egg is forbidden.
To avoid the complexity of these rules, Moshe Isserles records a custom not to eat any such eggs with blood spots.
If the egg was definitely unfertilized, many authorities rule that one may remove the blood spot and then eat the remainder of the egg. This is the case nowadays, when battery eggs form the majority of available produce.
Regarding the question of whether one must check an egg for blood spots, the Shulchan Aruch rules that one may eat hard-boiled eggs where checking is impossible. Moshe Isserles adds that checking is not required, but that a custom exists to check eggs if they are cracked during the daytime.
A contemporary Ashkenazi authority writes that while "halacha does not require" checking supermarket-bought eggs, "there is a minhag" to do so. Nevertheless, eggs are not checked in commercial settings where doing so would be expensive.
Gelatin
is hydrolysed collagen, the main protein in animal connective tissue, and therefore could potentially come from a non-kosher source, such as pig skin. Gelatin has historically been a prominent source of glue, finding uses from musical instruments to embroidery, one of the main historic emulsions used in cosmetics and in photographic film, the main coating given to medical capsule pills, and a form of food including jelly, trifle, and marshmallows; the status of gelatin in kashrut is consequently fairly controversial.Due to the ambiguity over the source of individual items derived from gelatin, many Orthodox rabbis regard it as generally being non-kosher. However, Conservative rabbis and several prominent Orthodox rabbis—including Chaim Ozer Grodzinski and Ovadia Yosef—argue that gelatin has undergone such total chemical change and processing that it should not count as meat, and therefore would be kosher.
Technically, gelatin is produced by separating the three strands in each collagen fiber's triple helix by boiling collagen in water. David Sheinkopf, author of Gelatin in Jewish Law and Issues in Jewish Dietary Laws, has published in-depth studies of the kosher uses of gelatin, as well as carmine and kitniyot.
One of the main methods of avoiding non-kosher gelatin is to substitute gelatin-like materials in its place; substances with a similar chemical behaviour include food starch from tapioca, chemically modified pectins, and carrageenan combined with certain vegetable gums—guar gum, locust bean gum, xanthan gum, gum acacia, agar, and others. Although gelatin is used for several purposes by a wide variety of manufacturers, it has started to be replaced with these substitutes in a number of products, due to the use of gelatin also being a significant concern to vegans and vegetarians.
Today manufacturers are producing gelatin from the skins of kosher fish, circumventing many of these problems.