In their most "biblical" form, Jewish Dietary Laws state:
- Pork, rabbit, eagle, owl, catfish, sturgeon, and any shellfish, insect or reptile are non-kosher.
- Other species of meat and fowl must be slaughtered in a prescribed manner to be kosher.
- Meat and dairy products may not be made or consumed together.
While Jewish Dietary Laws originated in the Bible (Leviticus 11 and Deuteronomy 17), they have been codified and interpreted over the centuries by rabbinical authorities.
Likewise, definitions of kosher have evolved in response to changes in the food industry, the Jewish People, and world culture.
Due to the growing complexity of foodstuffs, the need arose for kosher certifying agencies to determine the kosher status of prepared food. Today kosher certification labels are printed on the packages of kosher food.
As Jews lived in and adopted food traditions from different countries around the world and as different denominations of Judaism developed, Jewish definitions of kosher have become more varied over time. There are different Jewish ethnic cultures, different branches within Judaism, and various Jewish kosher certifying authorities in the United States that certify "kosher" based on rules that vary from liberal to conservative.
Furthermore, in recent times gentiles have become more interested in kosher food. Muslims, who account for 16 percent of the $100 billion-a-year U.S. kosher market, may buy a kosher food product because it fits the Quran's dietary laws of Halal. And people who are health-conscious may purchase something kosher because they believe it is healthier and safer as a result of the extra supervision. Various religious, cultural, health and quality reasons spark their interest in and color their definitions of kosher.