The use of lamb rennet paste in traditional sheep milk cheese production

The clotting of milk in cheese making is a key passage obtained by the use of enzymes or rennet. Several types of rennet are commercially available, they differ both on their origin (animal, vegetable, microbial and recombinant from genetically modified microorganism) and their physical state (liquid, powder or paste). Usually rennet is derived fromthe abomasa (fourth stomach or vell) of unweaned calves. Commercial preparations of calf rennet, available as liquid or powdered form, contains chymosin and a different number of proteases such as: pepsin A, gastricsin or pepsin B. This rennet do not contain lipolytic enzymes, which are denatured during the activation process of chymosin and pepsin zymogens. In Mediterranean countries, is common the use of lamb or kid rennet paste, always obtained from the abomasa of these small ruminants. Lamb rennet paste, besides milk-clotting and proteolytic enzymes (chimosin and pepsins), also contains a complex system of lipolytic enzymes. Lamb rennet paste is used in the production of some PDO traditional sheep milk cheeses, such as Idiazabal and Roncal in Spain, Fiore Sardo, Pecorino Romano, Canestrato Pugliese in Italy and Feta in Greece. The aim of this review is to summarize the current knowledge in lamb rennet paste including methods of preparation, enzymatic composition and factors influencing it, analytical aspects related to the enzymatic composition, proteolysis, lipolysis and sensory characteristics of cheeses.