The Basic Laws of Kashrus

Kosher means ‘fit’ or ‘proper’. In Jewish law we refer to foods which are permitted to be eaten as kosher. These laws are called the laws of kashrus. The laws of kashrus come primarily from the Torah with some additional Rabbinical decrees. The following is an outline of the basic laws of kashrus and their common application:

1. Only the meat and milk of certain animals is permitted. The Torah identifies these animals as having split hooves and 'chewing their cud'. In practical terms the only commonly used meat animals which are permitted are cows and sheep. There are many kosher animals (deer, buffalo and others) but none of them are used on a regular basis in America.
2. Not all birds are permitted. We know which birds are acceptable by means of tradition (the Torah lists the forbidden birds but the exact translation of some of these species is no longer known. Thus we can only eat birds known by tradition to be kosher.) Most commonly eaten birds (chicken, duck and turkey) are acceptable. (There is a minor controversy about turkey but most authorities maintain that it is acceptable.)
3. All fish with scales and fins are acceptable. This includes fish such as tuna and salmon.
4. All insects, crustaceans, shellfish, and other invertebrates are forbidden. It is therefore necessary to be careful when eating certain vegetables to be certain that they are not infested with insects. (There is one exception in the Torah for certain specific species of grasshoppers; however, the identity of the permissible species is no longer known.)
5. Even permitted animals and birds must be slaughtered in a very specific manner. A trained professional must perform this slaughtering.
6. It is forbidden to eat or cook milk and meat together. This includes poultry. It is also forbidden to use utensils that were used for cooking one to cook the other. This is why Jewish homes must have separate utensils for milk and meat.

In addition, there are numerous additional details which have to be dealt with. Therefore, in practical terms, most foods that are manufactured outside of one's home must be produced with reliable supervision to guarantee that they have been produced according to the laws of kashrus.