Whiteness change during heating and cooling of mozzarella cheese

Whiteness (L-value) changes in low-fat and low-moisture, part-skim Mozzarel la 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 c ooling. 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-sk im Mozzarella was heated. The white gel that formed was composed predominan tly of casein and casein proteolysis products. The gel might have been prod uced by heat-induced, hydrophobic protein-protein interactions, and it tend ed to dissociate when cooled. Formation of a gel during heating increased l ight scattering, which increased the L-value. The gel dissociated during co oling and no longer scattered light, which decreased the L-value. We hypoth esized that a gel, which was reversible, formed in the serum phase of chees e during heating and might have been responsible for the observed changes i n the L-value of low-fat Mozzarella cheese during heating and cooling. The additional fat in low-moisture, part-skim Mozzarella com pared with low-fat Mozzarella masked some of the color changes in the serum phase of low-mois ture, part-skim Mozzarella. A model was developed to describe the contribut ions of the casein matrix plus serum phase of Mozzarella cheese and the con tribution of fat to the changes in whiteness of Mozzarella cheese during he ating and cooling.