GPC/SEC-Light scattering for starch analysis

Introduction

Starches are polysaccharides produced by all green plants to store energy. They are the most important carbohydrates in the human diet, present in potatoes, wheat, maize (corn), and rice. Pure starch is a white powder insoluble in cold water. It consists of two types of molecules: the predominantly linear helical amylose (20-25%) and the lightly branched amylopectin (5-80%).

GPC/SEC-Multi Angle Laser Light scattering (GPC/SEC-MALLS) is the method of choice to characterize starches given their high molar masses and branching. MALLS allows measurement of absolute molar masses and radius of gyration, which can provide additional structural information. Sample preparation is a critical step and requires dedicated procedures, especially under aqueous conditions. The use of columns with large particle sizes and porosities ensure separations for molar masses up to several millions. Generally, native starches dissolve in DMS (Dimethylsulfoxide) and separate well in medium polar PSS GRAM columns. Alternatively, if aqueous conditions are required, SUPREMA columns can be used.

Experimental Conditions

Native waxy maize, tapioca, potato, and rice starch were wet-milled in order to determine the effect of milling on average molar mass (Mw) and molar mass distribution. 1 The molar mass distributions of the original pre-process and milled products were characterized by aqueous GPC/SEC with MALLS detection, using the following conditions:

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