. Morphology
Fig. 1 shows the morphology of native and AMT168 h starch
granules after pre-heated at different temperatures. Waxy corn
starch showed typical purple color for waxy starch after iodine
staining. Starch granules remained intact and no obvious swelling
was observed after pre-heated at 60 C. At 70 C, most of waxy corn
starch granules were gelatinized and swollen, while some granules
remained intact without obvious swelling. Waxy corn starch
granules were fully gelatinized at 80 and 90 C, and granule ghosts
were observed. For normal corn starch, granules also remained
intact at 60 C. Most of granules were swollen at temperature above
60 C but some granules still remained intact without swollen. The
swelling extent of gelatinized normal corn starch granules was less
profound than that of gelatinized waxy corn starch granules. The
granule sizes of Hylon V starch at 60e80 C were comparable and
the granules were still remained intact. Swollen granules of Hylon
V starch were found at 90 C, this was corresponding to the highly
restricted swelling characteristic of Hylon V starch.
AMT168 h starch of waxy corn showed intact granular
appearance at 60 C. While the starch was partially gelatinized at
70 C, no granule ghost was found at temperature above 80 C
and fully dispersed starch solutions were observed. This was
resulted from AMT which caused the breakdown of starch
granule structure during heating, and further led to the
increasing of C* value. Swelling for AMT168h starch of normal corn
after heated at 60 C was also not obvious, while at 80 and 90 C
granules with fissions were found instead of the fully dispersed
solution observed on AMT168 h starch of waxy corn. Similar result
was found for AMT168 h starch of Hylon V at 80 and 90 C except
that the fission in granules was not obvious. Solubility of AMT168 h
starch of normal corn at 80 and 90 C were higher than 50%
(Table 2), indicating that some starch granules were gelatinized,
collapsed and fully dispersed in water. Consequently, granule
ghosts were not observed for the gelatinized AMT168 h corn
starch. Results revealed that AMT induced the easily rupture of
gelatinized starch granules, especially for starch with low content
of amylose.
Fig. 1. Morp