The Effect of pH on the Rheological Properties of Reduced-fat Model Processed Cheese Spreads

Reduced-fat model processed cheese spreads were prepared from sodium caseinate, sunflower oil, water and sodium phosphate-based melting salts using a laboratory-scale processed cheese cooker equipped with direct steam injection and a scraped surface stirrer. These model processed cheese spread samples varied in pH from 5.0 to 6.0. The samples were analysed by dynamic oscillating rheology and penetrometry to determine mechanical properties. The samples changed from a solid-like character to a liquid character with the increase in pH. This corresponded to the shift in the mechanical spectra from that typical of a weak gel to that typical of a dilute solution. The hardness, moduli and viscosity of these samples decreased with increasing pH. The tan (ratio between the loss modulus (Gʹʹ) and elastic modulus (Gʹ)) increased with increasing pH, confirming the increasing liquid-like nature of the processed cheese as the pH increased.