Rennet is a complex set of enzymes produced in the stomachs of ruminant mammals. Chymosin, its key component, is a protease enzyme that curdles the casein in milk. In addition to chymosin, rennet contains other enzymes, such as pepsin and a lipase.

What is rennet and why is it used?

Rennet is the general name for enzymes that act on proteins in milk. It's purpose in a ruminant's stomach is to curdle milk for easier digestion, the same way it curdled our shepherd's drink. Rennet serves the same purpose in cheesemaking: it triggers coagulation.

Is rennet vegetarian or not?

What is vegetarian rennet? Vegetarian rennets are either vegetable-based (made from plants such as figs, nettles and thistles), microbial (produced using moulds and fungi sources) or made using genetically modified rennet.