Whiteness change during heating and cooling of Mozzarella cheese.

Whiteness (L-value) changes in low-fat and low-moisture, part-skim Mozzarella cheeses during heating (7 to 60 degrees C) and cooling (60 to 7 degrees C) were evaluated. In low-fat Mozzarella, a large increase in whiteness was observed during heating, and a decrease in whiteness was observed during cooling. In low-moisture, part-skim Mozzarella, the whiteness changes during heating and cooling were smaller. Serum phase was removed from low-fat and low-moisture, part-skim Mozzarella cheeses. White protein gels were formed when the isolated serum phase from either low-fat or low-moisture, part-skim Mozzarella was heated. The white gel that formed was composed predominantly of casein and casein proteolysis products. The gel might have been produced by heat-induced, hydrophobic protein-protein interactions, and it tended to dissociate when cooled. Formation of a gel during heating increased light scattering, which increased the L-value. The gel dissociated during cooling and no longer scattered light, which decreased the L-value. We hypothesized that a gel, which was reversible, formed in the serum phase of cheese during heating and might have been responsible for the observed changes in the L-value of low-fat Mozzarella cheese during heating and cooling. The additional fat in low-moisture, part-skim Mozzarella compared with low-fat Mozzarella masked some of the color changes in the serum phase of low-moisture, part-skim Mozzarella. A model was developed to describe the contributions of the casein matrix plus serum phase of Mozzarella cheese and the contribution of fat to the changes in whiteness of Mozzarella cheese during heating and cooling.