| The effect of chemical parameters on cheese structure and functionality was studied by modifying the calcium, salt content, and pH of cheese. Cheese blocks were high-pressure injected from zero to five times with water, solutions of different salts, or an acid solution 14 d after manufacture. Successive injections were performed 24 h apart. After 40–42 d of refrigerated storage, cheese structure was studied by using scanning electron microscopy and digital image analysis, and cheese functionality was characterized by texture profile analysis and melting test.; Increased salt content of cheese (2.7 versus 0.1%) caused the protein matrix to become more hydrated and to expand (P < 0.1), though the occurrence of syneresis resulted in decreased moisture content of cheese (P < 0.05). Salt injection increased cheese hardness and the initial rate of cheese flow, but it decreased cheese cohesiveness (P < 0.05).; Increased calcium content (1.8 versus 0.3%) and decreased pH of cheese (4.7 versus 5.3) caused contraction of the protein matrix (P < 0.05) and release of serum. Thus, the matrix became less hydrated, and the moisture content and weight of cheese decreased (P < 0.05). Calcium injection decreased the pH and melting of cheese, but it increased cheese hardness (P < 0.05). Acid injection promoted calcium solubilization and decreased calcium content of cheese (P < 0.05). Above pH 5.0 (5.0–5.3), acid injection decreased cheese hardness and increased the initial rate of cheese flow (P < 0.05). Below pH 5.0 (5.0–4.7), acid injection decreased cheese cohesiveness, and the initial rate and extent of cheese flow (P < 0.05).; In conclusion, modifying the chemical composition of cheese alters protein interactions, resulting in cheese with different structural and functional properties. Increased salt content of cheese (up to 2.7%) impairs protein-to-protein interactions, and its effect is most significant when salt content increases from 0 to 0.5%. Below 5.0 (5.0–4.7), the effect of pH predominates over calcium content, and decreased cheese pH promotes protein-to-protein interactions. Increased calcium content of cheese (up to 1.8%) also promotes protein-to-protein interactions, and the content of protein-bound calcium may be the major factor controlling the functionality of most cheeses. |
