Physicochemical and microstructural characterisation of green gram and foxtail millet starch gels.

The starch and starch gels from green gram (GG)
and foxtail millet (FM) were characterised for their
physicochemical, thermal and microstructural characteristics;
the features of shape and size were determined by
image analysis. Both GG and FM formed well-set gels at
9% concentration of starch. The fracture strain of the gels
was between 78 and 80% indicating non-brittle gels. The
peak temperatures of the native flour of GG (74.9 �C) and
FM (75.7 �C) were significantly higher than their corresponding
starch samples (72.2 and 75.0 �C). The conclusion
temperatures of the FM native flour (81.2 �C) and
starch (79.4 �C) samples were higher than the native GG
flour (79.9 �C) and GG starch (77.1 �C) samples. Starches
were nearly spherical as the roundness values were
between 0.88 and 0.95. Green gram starch was pentagonal
having an average diameter of 3.9–9.2 lm while foxtail
millet starch was spherical with a diameter of 4.9–10.1 lm.
The freeze-dried GG and FM starch gels showed cellular
structure containing organised hexagonal pores, bound by
thin pore walls; the GG starch gels deviated from the circular
shape as they had the highest elongation value of
4.21. The thicker pore walls were observed for GG starch
gels (0.88 lm) compared to that of FM samples (0.57 lm).
The higher pore wall thickness in the case of GG gel
showed the formation of junction zones.