Rennet or rennin is a natural complex of enzymes produced in any mammalian stomach to help a nursing baby digest mother’s milk. In the food industry, rennet is used as a coagulant – in cheese-making; in certain dairy products, including some yogurts; and in junket, a soft, pudding-like dessert.
Casein is the principal protein in milk. It’s found in the milk of all mammals, and, oddly enough, is often found in food items marked ‘non-dairy.’
A great many people become vegetarian for ethical reasons, in response to a strong sense that animals shouldn’t be mistreated on factory farms, or that they simply should not be killed for food. However, many individuals who eschew meat out of concern for animal interests continue to consume and use other animal products. Many vegetarians, in fact, upon removing flesh products from their diet, actually increase their intake of eggs and dairy, two products which result from extreme animal abuse.