Effect of calcium and water injection on structure-function relationships of cheese

Our objectives were to determine the effect of calcium and water injection on cheese structure and to relate changes in structure to changes in functional properties of cheese. Cheese with fat and moisture content similar to that of low-moisture part-skim Mozzarella was made according to a direct-acid, stirred/pressed-curd procedure. The cheese was then cut into blocks that were high-pressure-injected from one to five times, with either water or a 40% calcium chloride solution. Successive injections were performed 24 h apart. After 42 d of refrigerated storage, cheese microstructure and functionality were analyzed. When injected three or more times, water tended to increase cheese weight. The control, uninjected cheese, had the typical structure of a stirred/pressed-curd cheese: protein matrix interspersed with areas that originally contained fat and/or serum. Injecting water increased the area of cheese matrix occupied by protein, but it did not affect textural properties or melting of cheese. In contrast, when calcium was injected, a decrease in cheese weight was observed that was manifested through syneresis. The moisture content and pH of the cheese decreased as well. Calcium injection also decreased the area of cheese matrix occupied by protein. Cheese hardness increased, and cohesiveness and melting of cheese decreased upon calcium injection. We concluded that adding calcium to cheese alters how the proteins interact, which is manifested as changes in cheese microstructure. Such changes in cheese structure provide an understanding of changes in functional attributes of the cheese.