To as a function of mixing ratio at a fixed total concentration of
biopolymers is shown in Fig. 6. To exhibits a clear sigmoidal change
with increasing mixing ratio r, and begins to increase markedly
at r = 0.2. The change is very similar to that observed for isoelectric
point as a function of r [26]. The ratio of 0.2 might indicate a
stoichiometry of the complexation of gelation with KC. At mixing
ratios higher than 0.2, KC molecules are in excess and intramolecular
complexes are mainly formed [26]. This could imply a maximum
contacting between KC and gelatin, and facilitates the formation of
hydrogen bonds. On the contrary, when r < 0.2, gelatin molecules
are in excess and intermolecular complexes bridged by gelatin are
formed [26]. This might prevent the side-by-side alignment of KC
and gelatin chains and thus impedes the formation of extensive
hydrogen bonds (or hydrogen bonding network). Therefore, the
effect of mixing ratio on To should also be explained in the context
of electrostatic complexation.