Handbook of Size Exclusion Chromatography and Related ...

Stability of wheat starch glucan/DMSO solutions against mechanical stress
for increasing times of dissolution process was investigated by means of a dynamic
capillary viscosimeter by varying shear deformation (D). From these experiments
complex viscosity (h*) results as a contribution of viscous (h 0 : in-phase) and
elastic (h 00 : out-of-phase) contributions [Eq. (25)].
h ¼ h 0 þ ih 00
(25)
For the investigated wheat starch glucan non-negligible elastic contributions were
observed, at least in the initial states of dissolution. In general, according to
Ubbelohde viscosimeter investigations, viscosity decreases with increasing
periods of dissolution; additionally, elastic contributions, showing up as
D-dependence of complex viscosity, vanish for longer periods of dissolution
(Fig. 27). Typically, such types of D-dependence of viscosity will be found for
dynamically stabilized “soft gels,” a finding that perfectly matches the situation of
molecular dissolved glucans in the presence of minor amounts of supermolecular
glucan aggregates.
Figure 27 Wheat glucans. Visco-elastic properties of bulk solution for increasing
periods of dissolution process.
© 2004 by Marcel Dekker, Inc.