AGE-RELATED-CHANGES IN THE WATER PHASE OF MOZZARELLA CHEESE

Changes in the water-holding capacity of low moisture Mozzarella cheese during aging were evaluated by measuring the amount of serum expressed from the cheese upon centrifugation at 12,500 x g for 75 min at 25 degrees C. Low moisture Mozzarella cheeses (n = 3) were obtained the day after commercial manufacture and stored at 4 degrees C. Expressible serum was obtained at 2, 4, 8, 12, and 16 d after manufacture; analyzed for concentrations of CP and protein that was soluble at pH 4.6, Ca, P, K, Mg, Na, and Zn; and evaluated for proteins and peptides by urea-PAGE. Quantity of expressible serum decreased dramatically during storage, indicating substantial increase in water-holding capacity. Both CP and protein that was soluble at pH 4.6 in expressible serum increased during storage; however, CP content was higher and increased faster than protein that was soluble at pH 4.6. Urea-PAGE confirmed that unhydrolyzed alpha(s1)-, alpha(s2)-, and especially beta-CN accounted for a large share of the CP in the expressible serum. Concentration of Zn increased during aging, unlike that of other elements. A model that is based on the swelling and solubilizing action of NaCl on the protein matrix is proposed to account for the increases in water-holding capacity and the unhydrolyzed caseins in the water phase of Mozzarella cheese during aging.