Controlling the structure and rheological properties of model cheese systems

Changes in the rheological and microstructural properties of model cheese made from ultrafiltered milk and manufactured at three different pH/salt conditions were studied. Coagulation at a higher rennet concentration (R_c) and/or a higher temperature (T_c) formed harder cheese. In general this corresponded to increased aggregate and void size in the protein network as R_c and T_c increased. The final cheese pH also influenced both structure and texture. Harder cheese was formed at a lower pH for all R_c and T_c. The pH affected microstructure in a complex way. At a high pH of 5.2 coagulation did not occur at low R_c and T_c. At high R_c and T_c the aggregates formed were much denser than at lower pH. At a lower pH the general trend was for larger aggregates to be formed as pH increased. The results are explained in terms of the known effects of pH and salt on casein micelle structure, and the effects of differing R_c and T_c conditions on the rate of formation of the casein gel. Extent of casein particle fusion varied with coagulation temperature, pH and salt concentration.