Calf rennets

Calf rennets are the traditional milk-coagulating preparations extracted from the abomasum, the fourth stomach, of calves. The active enzyme is chymosin, which specifically cleaves kappa-casein to curdle milk, while pepsin is also present and contributes to proteolysis during ripening. For centuries calf rennets have been the standard coagulant in cheesemaking, prized for producing firm curds and clean flavours. Today they are joined by fermentation-produced chymosin and microbial rennets, but many traditional cheeses still specify animal rennet. Their supply depends on the veal industry, which is one reason cheesemakers developed fermentation-produced chymosin and microbial rennets as alternatives.