Fragmentation of Waxy Rice Starch Granules by Enzymatic Hydrolysis

Small starch particles were prepared by hydrolyzing waxy rice starch using α-amylase and then ultrasonicating in ethanol. Differential scanning calorimetry (DSC) revealed that a mild hydrolysis for 3 hr increased the melting enthalpy of the starch, which might indicate that the hydrolysis was select...

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Bibliographic Details
Published in:Cereal chemistry 2008-03, Vol.85 (2), p.182-187
Main Authors: Kim, J.Y, Park, D.J, Lim, S.T
Format: Article
Language:English
Subjects:
alpha-amylase
Biological and medical sciences
Cereal and baking product industries
crystal structure
diameter
differential scanning calorimetry
enthalpy
enzymatic hydrolysis
ethanol
Food industries
Fundamental and applied biological sciences. Psychology
glutinous rice
melting
particle size distribution
rice starch
Starch and starchy product industries
starch granules
ultrasonic treatment
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Summary:Small starch particles were prepared by hydrolyzing waxy rice starch using α-amylase and then ultrasonicating in ethanol. Differential scanning calorimetry (DSC) revealed that a mild hydrolysis for 3 hr increased the melting enthalpy of the starch, which might indicate that the hydrolysis was selective in the amorphous regions. Later, at 6-24 hr, the hydrolysis rate was reduced, with gradual decreases in DSC melting enthalpy, indicating that the crystalline regions were eroded simultaneously. X-ray diffraction patterns revealed the same trend as the DSC results. Average diameter of starch granules or particles was decreased dramatically in both volume- and number-based measurements (5.94 leads to 1.64 μm, and 0.45 leads to 0.18 μm, respectively) during the early stage of rapid hydrolysis (up to 3 hr). Native waxy rice starch exhibited a particle size distribution with a major peak at 5.6 μm. After hydrolysis for 3 hr, the volume distribution of starch granules changed to two major size peaks at 0.5 and 3.6 μm. The starch fragment of 0.5 μm was assumed to consist of crystalline blocklets. With excessive hydrolysis (24 hr) or ultrasonication, however, starch particle diameter was increased, indicating that the particles might be swollen or aggregated into clusters.
ISSN:0009-0352
1943-3638
DOI:10.1094/CCHEM-85-2-0182