Water in Dairy Products - Advanced Dairy Chemistry - page 477

Figure 11.12. Observed water self-diffusion coefficients as a function of protein concentration
(g/g) for (a) Na-caseinate solutions (*) and micellar casein dispersions ( ) and (b) micellar

casein dispersions ( ), acid gels (*) and rennet gels (h) (Mariette et al., 2002).

used in practice to remove water from the gels. Differences in mobility of the
hydrogen nuclei could not explain the difference in syneresis behaviour of
gels at high ( > 5.15) and low ( < 5.1) pH, syneresis rate being higher and
water content after syneresis lower in the first case. The microscopic struc-
ture of casein gels, characterized by a fractal dimension, was found to be
about the same for gels prepared by acidification or by rennet action. The
permeability coefficient was also very similar, in line with the D w results
reported above (Figure 11.12). The best explanation to the difference in the
ease of water removal appeared to be the dynamics of structure rearrange-
ments of the gel. Actually, the pH and temperature dependence of the
syneresis rate were found to parallel the tan obtained in rheological
measurements (Van Vliet and Walstra, 1994). The authors then concluded,