The physicochemical properties of corn starch (CS) and a component of granule shells (Cs) obtained through a granule shells separation process, were studied. The shells separation was accurately visualized and confirmed by SEM and TEM images. Both CS and Cs contained three components (amylopectin, intermediate fraction and amylose) with a Mw ranging from 4.11 × 107 to 11.42 × 107 g/mol. The amylose content of CS and Cs was in the following order: Cs-83 > CS > Cs-69 > Cs-76. There were no significant differences observed between CS and Cs-83 for the dynamic modulus, apparent viscosity, peak viscosity and final viscosity, while Cs-69 and Cs-76 exhibited a decreasing trend. The DSC results revealed that the transition temperatures of CS were significantly higher than those of Cs. There was an obvious decrease in the thermal degradation onset temperature (To) for the treated samples (CS:312.26 °C, Cs-69: 311.87 °C, Cs-76: 307.62 °C and Cs-83: 307.11 °C). The crystalline patterns of CS were converted from A-type to C-type during the granule shells separation process. The relative crystallinities of Cs were significantly lower than that of CS (26.87%). The FTIR results showed that intramolecular and intermolecular hydrogen-bonding (OH) of Cs were weakened after shells separation treatment.
Keywords: Fraction; Granule shells component; Molecular properties.
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