An outstanding parameter in cheese making is the type of coagulant, which greatly influences the characteristics of the final products. Proteolysis is the most important set of biochemical changes during ripening of most cheeses, and is carried out, in different magnitude, by proteolytic agents originated in milk, rennet (or rennet substitute), and starter and non-starter micro-organisms (Silva & Malcata, 2000). The demand for alternative sources of milk coagulants, to replace the expensive and limited natural rennet supplies, has increased (Esteves et al. 2001). All commercial enzymes employed as milk coagulant are aspartic proteinases, which are most active at acidic pH and preferentially cleave peptide bonds between residues with hydrophobic side-chains (Silva & Malcata, 1999).
