Rennets

Rennets are enzyme preparations used to cause coagulation of milk during cheesemaking. Traditionally they were extracted from the abomasum of young ruminants, mainly calves, and the active enzyme is chymosin, with some pepsin also present. Because of supply shortages and demand for vegetarian cheese, alternative forms are now widespread: microbial rennets, vegetable rennets, and genetically engineered chymosin produced by fermentation. Each type clots milk slightly differently, affecting curd firmness, whey drainage, and flavour development during ripening, so the choice of rennet is a real cheesemaking decision.