Effect of pH on the Chemical Composition and Structure-Function Relationships of Cheddar Cheese

Abstract

The objectives of this study were to determine the effect of pH on chemical, structural, and functional properties of Cheddar cheese, and to relate changes in structure to changes in cheese functionality. Cheddar cheese was obtained from a cheese-production facility and stored at 4 degrees C. Ten days after manufacture, the cheese was cut into blocks that were vacuum-packaged and stored for 4 d at 4 degrees C. Cheese blocks were then high-pressure injected one, three, or five times with a 20% (wt/wt) glucono-delta-lactone solution. Successive injections were performed 24 h apart. Cheese blocks were then analyzed after 40 d of storage at 4 degrees C. Acidulant injection decreased cheese pH from 5.3 in the uninjected cheese to 4.7 after five injections. Decreased pH increased the content of soluble calcium and slightly decreased the total calcium content of cheese. At the highest level, injection of acidulant promoted syneresis. Thus, after five injections, the moisture content of cheese decreased from 34 to 31%, which resulted in decreased cheese weight. Lowered cheese pH, 4.7 compared with 5.3, also resulted in contraction of the protein matrix. Acidulant injection decreased cheese hardness and cohesiveness, and the cheese became more crumbly. The initial rate of cheese flow increased when pH decreased from 5.3 to 5.0, but it decreased when cheese pH was further lowered to 4.7. The final extent of cheese flow also decreased at pH 4.7. In conclusion, lowering the pH of Cheddar cheese alters protein interactions, which then affects cheese functionality. At pH greater than 5.0, calcium solubilization decreases protein-to-protein interactions. In contrast, at pH lower than 5.0, the acid precipitation of proteins overcomes the opposing effect caused by increased calcium solubilization and decreased calcium content of cheese, and protein-to-protein interactions increase.

Cheese structure and current methods of analysis

“…The size of protein sub-aggregates is reduced from 10 to 2 nm as pH decreases from 5.3 to 4.7 (Pastorino, Hansen, & McMahon, 2003a), illustrating well the compaction and rearrangement of the micellar structure in fresh curd as the pH is reduced over time. At a pH of around 5.6, the casein structural units interact through calcium-mediated electrostatic bonds.…”

Effect of milk pasteurization and acidification method on the chemical composition and microstructure of a Mexican pasta filata cheese

“…aggregates (Pastorino, Hansen, & McMahon, 2003). Acidification by starter culture reduced gradually the pH of milk, so that the extent of the decrease in the interactions between proteins was cushioned.…”

Towards the classification of cheese variety and maturity on the basis of statistical analysis of proteolysis data—a review

“…Important variables at this stage of the manufacturing process include the starter species and strains; the type and amount of coagulant used (Broome & Limsowtin, 1998); the coagulation temperature; the rate of acid development; and the pH at curd setting (Johnston, Dunlop, Coker, & Wards, 1994). Important post-coagulation variables may include the size of the curd particles after cutting; the cook temperature; curd washing (whey may be removed and water added); the pH of the curd at whey draining (Holmes, Duersch, & Ernstrom, 1977;Larsson & Andre´n, 1997); the temperature of the curd at stretching (for Mozzarella); the method of salting (dry or brine) and the amount of salt used (Pastorino, Hansen, & McMahon, 2003a); pressing; and the final cheese pH (Watkinson et al, 2001;Pastorino, Hansen, & McMahon, 2003b;Sheehan & Guinee, 2004).…”