3.5. Gel microstructureeelectron microscopy patters
Typical SEM microphotographs (in the same scale) of morphological patterns of 20 g/100 g native gelatin gel and the same gel with addition of only 0.5 g/100 g ofk-carrageenan are compared in Fig. 10.
One can say with confidence that the difference is striking.
Supramolecular structure of native gelatin formed due to the
self-organization process is characterized by transversal collagenlike helix with concentration dependent size (Fig. 10a). The fibrils form a network. Gel structure also includes discrete zones (cells)
distributed along fibrils inside a network, which presumably
consist mainly of non-helical pieces of macromolecules.
It is seen that addition of even small quantity k-carrageenan
leads to radical changes in the gel structure (Fig. 10b). Polysaccharide initiates some interactions between helix zones in
gelatin due to appearance ofk-carrageenanegelatin polyelectrolyte
complexes. Similar transformations of the morphological pattern
can be observed by application of other polysaccharides,
for instance, gellan (Pranoto et al., 2007) and sodium alginate
(Voron'ko, Derkach,&Izmailova, 2002). The modification mechanism ofk-carrageenan addition is associated with the evident hardening of the gelatin gel structure and it was quite demonstrative in the results of rheological studies.