Atomic Force Microscopy Investigation of Disorder Process on Rice Starch Granule Surface
ABSTRACT Precise ultra-structures of rice starch granules have been analyzed by atomic force microscopy combined with a structure-disorder process at ambient conditions. Atomic force microscopy is a useful technique to obtain images under atmospheric condition with a nanometer-scale resolution. The images obtained by a high-resolution tapping mode revealed a detailed surface ultra-structure of native rice starch granule with a diameter of approximately 100 nm. The ultra-structures were arranged in series like a chain, and the chain was bundled together into a rod or larger column. After a disorder process using plasticizing/lyophilization of the granules, a significant change in the organization of the surface morphology was detected. Some fine particles of approximately 30 nm in diameter were observed, which might correspond to the individual single cluster in the crystalline region of the starch granule.
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ABSTRACT: We studied the nano-scale properties of dry native starch granules of wheat and potato by atomic force microscopy. Whereas at the macroscale the mechanical behavior of starch powders is known, its origin at sub-granule level has still to be understood. We observed fine morphological structures, such as the growth rings and blocklet domains, with minor differences between the two starches. The granules, embedded in resins with known stiffness, were analyzed with lateral-force, force-distance and force-modulation microscopy. Integer granules exhibited a similar friction coefficient to the tip, decreased with respect to the embedding resin, without occurrence of stick-slip. The compressive modulus measured was also similar for both starch types (∼1.4 GPa in indentation and ∼2.0 GPa in dynamic mode), with slightly higher values for potato starch. On sectioned granules, the effect of aging in air likely due to moisture produced in both starches a strong reduction in apparent modulus (∼0.2 GPa).Journal of Food Engineering 05/2014; 128:96–102. · 2.28 Impact Factor
- Value in Health 11/2011; 14(7). · 2.19 Impact Factor
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ABSTRACT: Wheat starches at different stages of maturities were evaluated for their iodine absorption properties by measuring the ratio of absorption to reflection spectra (K/S) and crystalline structure by using wide angle X-ray scattering (WAXS). The surface of starch granules was also visualized by using atomic force microscopy (AFM). The K/S spectral data demonstrated different levels of mobility of starch polymers at different stages of maturity and the mobility of longer chain polymers with increasing moisture contents. Iodine did not change the characteristic A-type crystalline pattern. However, the extent of effect of iodine on starch crystallinity was affected by maturity and moisture content of starches. AFM images of iodine exposed starches supported the interaction of iodine molecules with starch polymers. Differences in surface features were observed for different maturities.Carbohydrate Polymers. 01/2010;