The effect of pH on the microstructure, rheological and functional properties of halloumi-type cheese: pH-structure-function relationships

This study investigated the impact of pH on the microstructure and functional properties of Halloumi-type cheese produced from cow milk. The optimal pH for non-melting during frying and ideal oil release was above 6.41 or below 4.69. Lowering pH to 5.33 reduced rennet coagulation time (RCT) to 4.5 min. Further pH decrease reduced calcium (Ca) content by 89.4 % but increased water-holding capacity (WHC) by 16.7 %. As pH dropped from 6.53 to 5.33, colloidal calcium phosphate (CCP) dissolved, weakening the protein network via electrostatic repulsion, which decreased storage modulus, increased melt flow, and enhanced free oil release. Below pH 4.69, hydrophobic interactions and hydrogen bonding strengthened, increasing gel strength and reducing melt flow and oil release. Microstructure showed larger pores and fat aggregation at low pH, and FTIR confirmed altered protein interactions. Thus, pH critically regulates meltability by modifying calcium content and protein interactions.