Self-Assembly of Starch Spherulites as Induced by Inclusion Complexation with Small Ligands - Food Colloids: Self-Assembly and Material Science - page 121

rod-like spherulites with dimensions from 10 to 15 mm, irregular spherulites
with diameters from 20 to 50 mm and rather large spherulites from 20 to 90 mm
in size, which presented a Maltese cross and a banded extinction pattern when
viewed under polarized light. Most likely the spherulites shown in Figure 1
correspond to different stages of spherulitic growth, as also shown for chitosan
crystals. 15 Late stages of spherulitic growth lead to spherical structures that
display a distinct Maltese cross.
The appearance of spherulites is linked to the helix-forming tendency of
starch in the presence of lactones and the subsequent formation of ordered
structures. The complexation of amylose can be viewed as an interaction that
drives this polymer out of solution, due to the strong association tendency of
the helical amylose segments, in order to escape the unfavourable interaction
with water. Spherulites grown by the addition of lactones to starch dispersions
present the typical V h -type crystalline packing of amylose inclusion complexes
as characterized by wide-angle X-ray diffraction (Figure 2). The reflections at
7.51, 13.01 and 20.01 correspond to crystalline assemblies of single-left-handed
amylose helices with six glucose units per helical turn. The X-ray diffractogram

reference

γ -hepta-

γ -nona-

γ -deca-

γ -dodeca-

-deca-

δ

δ -dodeca-

5 10 15 20 25 30

Scattering angle 2 θ [degrees]

Figure 2 X-ray diffraction diagrams of freeze-dried potato starch dispersions without
addition (reference) and with addition of various lactones. Relative intensity is
plotted against scattering angle