Waxy maize starch was subjected to -
-amylase (Bacillus licheniformis) hydrolysis in buffered medium to
determine the evolution of reaction in quantitative terms and also in terms of the morphology and crys-
tallinity of the partially hydrolyzed starch granules. Gathered data allowed studying the pattern of action
of this -
-amylase over waxy maize starch granules, with particular focus on a preferential hydrolysis of
the amorphous regions of starch. Results showed that waxy maize starch hydrolysis followed a two-stage
kinetic profile with an initial stage characterized by high reaction rate, followed by a slower second stage.
The change of hydrolysis rate occurred at approximately 6 h of reaction, a time for which X-ray diffrac-
tion data quantitatively analyzed by three different techniques showed a maximum of crystallinity in
partially hydrolyzed granules. Scanning electron microscopy images illustrated the action of -
-amylases
which implied the exoerosion of the granules surface, the entry of -
-amylases into the granules through
radial channels, their endoerosion towards the granule exterior, and their fragmentation. Fragmentation
of waxy maize starch granules revealed internal layered structures of starch which were interpreted as
hydrolyzed/non-hydrolyzed growth rings. Under the conditions chosen, kinetic, electron microscopy and
X-ray data all gave evidence of a preferential action of -
-amylase from Bacillus licheniformis towards the
less ordered regions of waxy maize starch. Results showed that, provided the proper hydrolysis time is
chosen, starch granules with increased crystallinity can be obtained by a pure enzymatic treatment.
Waxy maize starch was subjected to -
-amylase (Bacillus licheniformis) hydrolysis in buffered medium to
determine the evolution of reaction in quantitative terms and also in terms of the morphology and crys-
tallinity of the partially hydrolyzed starch granules. Gathered data allowed studying the pattern of action
of this -
-amylase over waxy maize starch granules, with particular focus on a preferential hydrolysis of
the amorphous regions of starch. Results showed that waxy maize starch hydrolysis followed a two-stage
kinetic profile with an initial stage characterized by high reaction rate, followed by a slower second stage.
The change of hydrolysis rate occurred at approximately 6 h of reaction, a time for which X-ray diffrac-
tion data quantitatively analyzed by three different techniques showed a maximum of crystallinity in
partially hydrolyzed granules. Scanning electron microscopy images illustrated the action of -
-amylases
which implied the exoerosion of the granules surface, the entry of -
-amylases into the granules through
radial channels, their endoerosion towards the granule exterior, and their fragmentation. Fragmentation
of waxy maize starch granules revealed internal layered structures of starch which were interpreted as
hydrolyzed/non-hydrolyzed growth rings. Under the conditions chosen, kinetic, electron microscopy and
X-ray data all gave evidence of a preferential action of -
-amylase from Bacillus licheniformis towards the
less ordered regions of waxy maize starch. Results showed that, provided the proper hydrolysis time is
chosen, starch granules with increased crystallinity can be obtained by a pure enzymatic treatment.
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