Effect of cheese pH and ripening time on model cheese textural properties and proteolysis

The effect of pH on the textural properties and proteolysis of semi-hard cheese was determined with minimal confounding effects from other compositional variables. Glucono-delta -lactone was used in model cheeses to control final pHs to approximately 5.2-6.2 (approximately 42.5% moisture). At lower pH, alpha (s1)-casein breakdown was faster (probably because chymosin was more active at lower pH); at higher pH, beta -casein breakdown was faster (probably because plasmin was more active at higher pH). When the cheese was 2 days old (minimal proteolysis), increasing the pH from 5.2 to 6.2 caused the cheese to be less crumbly (fracture strain rose 72%) and more firm (fracture stress rose 34%). At 87 days, the cheeses had similar or slightly smaller pH-induced changes in rheological properties, and proteolysis in addition to pH would have influenced these changes. pH interactions with storage time were significant for fracture properties, adhesion area (all P < 0.0001) and modulus of deformability (P = 0.04). Moisture interactions with storage time were significant for modulus (P = 0.0075) and fracture strain (P = 0.02). (C) 2001 Elsevier Science Ltd. All rights reserved.