Contribution of coagulant to proteolysis and textural changes in Cheddar cheese during ripening

Proteolysis and changes in the rheological properties of Cheddar cheese during ripening were compared, in cheeses containing active (recombinant chymosin or porcine pepsin) or inactivated (porcine pepsin) coagulant. Modification to the cheesemaking process extensively denatured porcine pepsin. Very little proteolysis occurred in the modified pepsin cheese although some alpha(s1)-casein was hydrolysed to alpha(s1)-I-casein (alpha(s1) f24-199) and other peptides during the later stages of ripening, perhaps due to the action of the indigenous milk acid proteinase, cathepsin D, or to some residual pepsin activity in the cheese. In the control cheeses, porcine pepsin was less proteolytic than chymosin, as indicated by polyacrylamide gel electrophoresis or the formation of water-soluble nitrogen, but there was little difference in the concentration of free amino acids between these two cheeses. Some differences were observed between the peptides produced by chymosin or pepsin. As the cheeses matured, cohesiveness, the force required to fracture the cheeses and distance to fracture decreased. Modification to the cheesemaking process affected all the rheological parameters measured after 60 and/or 180 days ripening. The type of coagulant had no effect on hardness or the force required to fracture the cheeses but significant differences were found between the chymosin and pepsin cheeses with regard to cohesiveness and distance to fracture. (C) 1997 Elsevier Science Ltd. All rights reserved.