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United States Department of Agriculture

Agricultural Research Service

Research Project: Enhancement of Hard Spring Wheat, Durum, and Oat Quality

Location: Cereal Crops Research

Title: Analysis of Cereal Starches by High Performance Size Exclusion Chromatography

Authors
item Simsek, Senay -
item Whitney, Kristin -
item Ohm, Jae-Bom

Submitted to: Journal of Food Analytical Methods
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: April 13, 2012
Publication Date: February 1, 2013
Citation: Simsek, S., Whitney, K., Ohm, J. 2013. Analysis of Cereal Starches by High Performance Size Exclusion Chromatography. Journal of Food Analytical Methods. 6(1): 181-190.

Interpretive Summary: Starch has unique physicochemical characteristics. Most starch granules are a mixture of two kinds of starch molecules: highly branched molecule named amylopectin, and a basically linear molecule named amylose. The objective of this study was to develop a simple, one-step and accurate method for simultaneous determination of amylose:amylopectin ratio as well as size of starch molecules in whole meal cereal samples. Starch from samples of spring wheat, barley, oat, rye, buckwheat, rice, durum wheat and corn were extracted by precipitation of starch by ethanol after dissolving flour in KOH-urea solution by heating. Starch molecules were separated into amyloses and amylopectins according to their molecule sizes, using high performance size exclusion chromatography (HPSEC) system. All the fractions separated by HPSEC were not contaminated with non-starch polysaccharides. Average molecular size of starch molecules were calculated using a series of molecular size standards, gel permeation chromatography grade dextrans. The method described in this study can be used to determine starch amylose:amypectin ratio and average size of cereal starch molecules using as low as 25mg whole meal samples.

Technical Abstract: Starch has unique physicochemical characteristics among carbohydrates. Most starch granules are a mixture of two sugar polymers: a highly branched polysaccharide named amylopectin, and a basically linear polysaccharide named amylose. The objective of this study was to develop a simple, one-step and accurate method for simultaneous determination of amylose:amylopectin ratio as well as weight-averaged molecular weights of starch in whole meal cereal samples. Starch from samples of spring wheat, barley, oat, rye, buckwheat, rice, durum wheat and corn were extracted using KOH, urea and ethanol. Starch samples were solubilized before they were run on the high performance size exclusion chromatography (HPSEC) system with a refractive index detector. To verify the identity of the peaks, fractions were collected and then soluble starch and beta-glucan assays were performed in addition to gas chromatography analysis. All the fractions contained only glucose, which indicated there was no contamination from non-starch polysaccharides. Soluble starch assays matched with the HPSEC profiles. Weight-averaged molecular weights were calculated using a series of gel permeation chromatography grade dextrans. The method described in this study can be used to determine amylose:amypectin ratio and weight-averaged molecular weight of cereal starches using as low as 25mg whole meal samples.

Last Modified: 7/30/2014
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