All foods and their components and derivatives are divided into 4 categories:
These categories are explained below.
Meat and its derivatives may only be consumed from Kosher species:
Even a very small amount of meat (or its derivatives) in a product gives that product a “meat” status.
This includes milk and all its derivatives. It does not include eggs (see Pareve section below).
Milk from a non-Kosher animal (see Meat section above), e.g. pig or camel, is not Kosher.
Milk must be guaranteed to be sourced from a Kosher animal only. Some, therefore, have the custom of not using milk unless supervised from the time of milking (Cholov Yisroel).
Even a very small amount of dairy (or its derivatives) in a product gives that product a “dairy” status.
Furthermore, food processed with heat on equipment previously used for a dairy product, acquires dairy status unless the cleaning process complies with kosher sterilisation.
This is the category for food that does not fall under the above two categories i.e. neither meat nor dairy.
Included under 'pareve' are:
Eggs: These may only be obtained from a Kosher bird;
Plants: Biblical rules control the use of agriculture produce: for produce grown in the Land of Israel a modified version of the Biblical tithes must be applied, including Terumas HaMaaser, Maaser Rishon, Maaser Sheni, and Maaser Ani (untithed produce is called tevel and may not be consumed); the fruit of the first three years of a tree's growth or replanting are forbidden for eating or any other use as orlah; produce grown in the Land of Israel in the seventh year is Shvi'is (and unless managed carefully is forbidden as a violation of the Shmitah-Sabbatical year);
Fish: These must have fins and scales that can be easily removed without damaging the skin of the fish. Others note that the scales must also be visible. Shellfish and non-fish water fauna are not Kosher. For a listing of commonly available Kosher fish please see the category 'Fish-Fresh' in the Food Guide (login required).
Drinks: . Drinks by and large should be Kosher except if they contain any of the intrinsically non-Kosher foodstuffs (such as cochineal, gelatine, cognac oil, grape juice, etc.). Because of the prohibition of meat/milk mixture (see Mixtures section), drinks containing dairy can be problematic. Juices, cordials and soft drinks may contain added flavourings that may contain non-Kosher components.