Initial phase solubilization of normal corn starch by methyl sulfoxide (DMSO): Evidence from scanning electron microscopy and size exclusion chromatography
1997
Mua, J.P. | Rosowski, J.R. | Jackson, D.S.
English. Initial structure and solubility changes of normal corn and starch granules, dispersed in varying methyl sulfoxide (DMSO) concentrations were investigated by scanning electron microscopy (SEM) and high-performance size exclusion chromatography (HPSEC). Larger granules from starches held for 6 or 15 min and air dried showed increased surface etching with increasing DMSO concentration (0-70%): smaller granules showed surface peeling at 70% DMSO. At 90% DMSO, larger granules fractures into smaller pieces, while smaller granules showed full surface erosion. At 100% DMSO, large chunks eroded off both large and small granules. With 100% DMSO, a sheet-like layer formed over a mass of ruptured granules during drying, suggesting that in the absence of water, DMSO dissolves part of the granule, forming a viscous solution which may limit further DMSO granule dispersion. Granules processed with critical-point drying showed additional evidence of attack. HPSEC polymer solubility increased with DMSO concentration (0-90%). At 100% DMSO, however, there was no measured solubility. Similar solubilities for starches held at 6 or 15 min (0-90% DMSO) suggest that DMSO may require an external force such as heat to facilitate polymer solubility. More amylopectin of a lower molecular weight was solubilized at 6 min, while more amylose was solubilized at 15 min. This suggests that granule surfaces were mostly composed of amylopectin under development, while amylose was mostly confined to amorphous regions inside the granule.
Show more [+] Less [-]German. Die Anfangsstruktur- und Phasenaufschluss-Veraenderungen von Maisstaerkekoernern, dispergiert in verschiedenen Methylsulfoxid-(DMSO)-Konzentrationen wurden durch Raster-Elektronenmikroskopie (SEM) und Hochleistungs-Groessenausschluss-Chromatographie (HPSEC) untersucht. Die Staerkekoerner wurden bei 6 oder 15min bei verschiedenen DMSO-Konzentrationen dispergiert und dann luftgetrocknet. HPSEC-Polymerloeslichkeit vergroesserte sich mit der DMSO-Konzentration. Mehr Amylopektin von geringerem Molekulargewicht wurde nach 6 min geloest, waehrend nach 15 min mehr Amylose geloest wurde. Dies weist darauf hin, dass die Kornoberflaechen bei der Entwicklung hauptsaechlich von Amylopektin zusammengesetzt waren, waehrend Amylose groesstenteils in amorphen Regionen des Korns eingeschlossen war.
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