2.3. Characterization of partially hydrolyzed granules
Drops of partially hydrolyzed starches/water suspensions (1%,
w/v) were deposited on microscope glasses and dried at 40 ◦C for
5 min. Samples were then coated with gold using an ion sputter
coater, and observed by use of a scanning electron microscope
Zeiss Supra 40 with field emission gun operated at 3 kV. At each
hydrolysis time chosen, the granules size distribution as well as
the growth rings thickness distribution were determined by use
of ImageJ and JMicroVision v.1. 2.7. software according to a length
scale provided by the user. More than 35–60 granules/growth rings
were considered for each determination.
X-ray diffraction (XRD) analysis was performed on native and
selected hydrolyzed starches in a Rigaku diffractometer with Bragg
Bentano geometry, and Cu radiation in the range of 2 = 5–50◦.
Samples were measured under temperature and humidity room
conditions. The diffractograms obtained were carefully smoothed
and normalized with respect to the highest intensity. The crystallinity
of native and partially hydrolyzed starch granules was
then quantified in terms of the crystallinity index (CI), a parameter
frequently used to describe the relative amount of crystalline
material in a sample. Three different methods dispersedly found in
the literature for the determination of crystalline and amorphous
contributions in starch were used, namely the “two-phase” method
adapted from Nara and Komiya (1983); a deconvolution method
assuming Lorentzian peaks which fitted experimental XRD data by
use of Origin software, and an adaptation of Segal’ method derived
and widely used for a rapid estimation of cellulose crystallinity
index (Segal, Creely, Martin, & Conrad, 1962).
2.3. Characterization of partially hydrolyzed granulesDrops of partially hydrolyzed starches/water suspensions (1%,w/v) were deposited on microscope glasses and dried at 40 ◦C for5 min. Samples were then coated with gold using an ion sputtercoater, and observed by use of a scanning electron microscopeZeiss Supra 40 with field emission gun operated at 3 kV. At eachhydrolysis time chosen, the granules size distribution as well asthe growth rings thickness distribution were determined by useof ImageJ and JMicroVision v.1. 2.7. software according to a lengthscale provided by the user. More than 35–60 granules/growth ringswere considered for each determination.X-ray diffraction (XRD) analysis was performed on native andselected hydrolyzed starches in a Rigaku diffractometer with BraggBentano geometry, and Cu radiation in the range of 2 = 5–50◦.Samples were measured under temperature and humidity roomconditions. The diffractograms obtained were carefully smoothedand normalized with respect to the highest intensity. The crystallinityof native and partially hydrolyzed starch granules wasthen quantified in terms of the crystallinity index (CI), a parameterfrequently used to describe the relative amount of crystallinematerial in a sample. Three different methods dispersedly found inthe literature for the determination of crystalline and amorphouscontributions in starch were used, namely the “two-phase” methodadapted from Nara and Komiya (1983); a deconvolution method
assuming Lorentzian peaks which fitted experimental XRD data by
use of Origin software, and an adaptation of Segal’ method derived
and widely used for a rapid estimation of cellulose crystallinity
index (Segal, Creely, Martin, & Conrad, 1962).
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