Of the "beasts of the earth" (which basically refers to land mammals with the exception of swarming rodents), you may eat any animal that has cloven hooves and chews its cud. Lev. 11:3; Deut. 14:6. Any land mammal that does not have both of these qualities is forbidden. The Torah specifies that the camel, the rock badger, the hare and the pig are not kosher because each lacks one of these two qualifications. Sheep, cattle, goats and deer are kosher.
Of the things that are in the waters, you may eat anything that has fins and scales. Lev. 11:9; Deut. 14:9. Thus, shellfish such as lobsters, oysters, shrimp, clams and crabs are all forbidden. Fish like tuna, carp, salmon and herring are all permitted.
For birds, the criteria is less clear. The Torah lists forbidden birds (Lev. 11:13 -19; Deut. 14:11 -18), but does not specify why these particular birds are forbidden. All of the birds on the list are birds of prey or scavengers, thus the rabbis inferred that this was the basis for the distinction. Other birds are permitted, such as chicken, geese, ducks and turkeys.
Of the "winged swarming things" (winged insects), a few are specifically permitted (Lev. 11:22 ), but the Sages are no longer certain which ones they are, so all have been forbidden.
Rodents, reptiles, amphibians, and insects (except as mentioned above) are all forbidden. Lev. 11:29-30, 42-43 .
Some authorities require a post-mortem examination of the lungs of cattle, to determine whether the lungs are free from adhesions. If the lungs are free from such adhesions, the animal is deemed "glatt" (that is, "smooth"). In certain circumstances, an animal can be kosher without being glatt; however, the stringency of keeping "glatt kosher" has become increasingly common in recent years.
As mentioned above, any product derived from these forbidden animals, such as their milk, eggs, fat, or organs, also cannot be eaten. Rennet, an enzyme used to harden cheese, is often obtained from non-kosher animals, thus kosher hard cheese can be difficult to find.
Kosher slaughtering
The mammals and birds that may be eaten must be slaughtered in accordance with Jewish law. (Deut. 12:21). We may not eat animals that died of natural causes (Deut. 14:21 ) or that were killed by other animals. In addition, the animal must have no disease or flaws in the organs at the time of slaughter. These restrictions do not apply to fish; only to the flocks and herds (Num. 11:22 ).
Ritual slaughter is known as shechitah, and the person who performs the slaughter is called a shochet, both from the Hebrew root Shin-Chet-Tav, meaning to destroy or kill. The method of slaughter is a quick, deep stroke across the throat with a perfectly sharp blade with no nicks or unevenness. This method is painless, causes unconsciousness within two seconds, and is widely recognized as the most humane method of slaughter possible.
Another advantage of shechitah is that ensures rapid, complete draining of the blood, which is also necessary to render the meat kosher.
The shochet is not simply a butcher; he must be a pious man, well-trained in Jewish law, particularly as it relates to kashrut. In smaller, more remote communities, the rabbi and the shochet were often the same person.
