Effect of sodium chloride on the serum phase of Mozzarella cheese

The objective was to compare changes in the serum phase of brine-salted and unsalted Mozzarella cheeses during aging to elucidate the impact of NaCl on the serum phase and physico-chemical changes. Brine-salted and unsalted blocks of low moisture, part-skim Mozzarella cheese that had been commercially produced were analyzed for expressible serum after 2, 4, 6, 8, and 10 d of storage at 4 degrees C. The amount of expressible serum decreased during aging of both brine-salted and unsalted cheeses; however, amounts were higher for unsalted cheese and decreased more slowly than for brine-salted cheese. The amounts of protein that were insoluble at pH 4.6 in the expressible serum increased dramatically during aging of brine-salted cheeses, but increased only slightly during aging of unsalted cheeses, Urea-PAGE and SDS-PAGE confirmed that intact alpha(s1)-casein (CN), alpha(s2)-CN, beta-CN, and para-kappa-CN were present at higher concentrations and increased to a greater extent in the expressible serum of brine-salted than in unsalted Mozzarella cheeses. The data are consistent with the hypothesis that NaCl in the serum phase of Mozzarella cheese promotes microstructural swelling, a concomitant increase in water-holding capacity and the solubilization of intact caseins from the paracasein matrix.