50 Molecular characterization of starch with HPSEC-MALLS-RI system.

S. LIM, S. You, and J. Han. Graduate School of Biotechnology, Korea University.

Laser-light scattering (LS) analysis is a popular tool for characterizing the molecular properties of various macromolecules from synthetic and biological origins. Not only the absolute value of molecular weight, but the radius of gyration, oligomeric conformations, and solvent interactions can be measured. Basic theory behind the analysis is Rayleigh-Debye-Gans model where the scattering intensity of a polymer in a dilute solution depends on its molecular weight and concentration in the solution. This technique is non- invasive, fast and not dependant upon the Stokes radius of the macromolecules nor calibration curve. There are usually two analytical modes used with LS analysis: batch and chromatographic modes. In batch mode, measurement is performed once with a mixture of polymers in solution, whereas in chromatographic mode, comprising polymers can be fractionated and measured individually. Therefore, more information of the polymers could be obtained with the chromatographic mode. Size exclusion, ion-exchange, reverse phase or other types of columns can all be adaptable. Other techniques such as field flow fractionation can be also used for the separation of the polymers in the mixture. Recently a number of publications report the molecular characteristics of starches using the LS analysis at batch or size exclusion chromatographic mode. But the published results with the starches of similar origins vary widely. Two facts should be carefully considered in the analytical procedure: (1) huge molecular size of amylopectin, and (2) instability of amylose. Therefore, sample preparation and selection of the columns affect the data significantly. The published data under different analytical conditions and optimization approaches will be discussed.