Flow behaviour of gellan sol with selected cations.

An understanding of the flow behaviour of the sols
before gel formation is important for developing nutrient
enriched gels. The influence of cations like CaCl2 (0.05 and
0.1%,w/w) and FeSO4 (0.05 and 0.1%,w/w) on the rheological
properties of 1 % gellan sol (w/w) prior to gelling was investigated.
The apparent viscosity, reported at a shear-rate of 100 s-1,
indicated that the gellan dispersion without any cation possessed
lower values compared to other samples containing different
cations. The Cross model provided the best fit (0.97≤r≤0.99,
p≤0.01) compared to moderate fitting to power law model
(0.94≤r≤0.98). Among the different Cross model parameters,
the zero-shear viscosity (ηo) increased with the addition of CaCl2
and FeSO4, and with an increase in their concentrations. Zeroshear
viscosity values were 0.46 Pas for gellan sol, 0.79 Pas for
gellan with 0.05 % (w/w) CaCl2, 1.41 Pas for gellan with 0.1%
CaCl2, 3.85 Pas for gellan with 0.05 % FeSO4 and 4.33 Pas for
gellan with 0.1 % FeSO4. An increase in cation concentration
from 0.05 to 0.10 % (w/w) marginally increased the relaxation
time (λ) values indicating the development of more solid characteristics
in the sol.