In contrast to the above, the results of Guinee
et al.(2002) indicate that the pH of the mozzarella
cheese increased gradually during storage at 4C
for 70 days. The increase in pH during storage was
also noted by Metzger et al. (2001) for low fat, and
by Guo et al. (1997) for full fat in mozzarella
cheeses made using a starter culture. The increase
in cheese pH may be caused by the solubilisation
of calcium phosphate released phosphate ions
which buffer the system or associated with the
gradual increase in para-casein hydration and the
increased availability of various protein residues
(e.g. e- and a-carboxyl groups of aspartic and
glutamic acids), which combine with H+ during
storage and thereby reduce the hydrogen ion activity
of the moisture phase of the cheese. In turn, the
increase in para-casein hydration may be affected
by changes in the equilibrium concentrations of
soluble and colloidal calcium phosphate (Guo
et al. 1997), migration of salt in moisture in
contact with the protein phase (e.g. ice structure
water, imbibed water; Geurts et al. 1974a,b) and
proteolysis.