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Characterizing the Internal Structure of High Amylose Maize Starches

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Title: Characterizing the Internal Structure of High Amylose Maize Starches
Author: Peymanpour, Ghazal
Department: Department of Food Science
Program: Food Science
Advisor: Marcone, Massimo
Abstract: High amylose maize, a mutant lacking starch branching enzyme IIb (SBEIIb), has a modified starch with more than 50% apparent amylose content. Study of the internal structure of starch components is important, since it will lead to a better understanding of starch biosynthesis and functional properties. This study investigated the molecular and internal structures of all starch components from Hylon V, Hylon VII, Hylon VIII and normal maize. In comparison to normal maize starch, all Hylon samples contained high amounts of intermediate materials, which appeared to contribute to an apparently very high content of amylose. Among all the isolated starch components, amylopectin had the most significant structural differences in all samples. All the Hylon samples possessed amylopectins with high amounts of low molecular weight (LMW) molecules and longer chain lengths compared to normal maize amylopectin. The internal chain segments of all iii amylopectins were mainly of intermediate length, the amount of which decreased in the order of Hylon VIII > Hylon VII > Hylon V > normal maize. Clusters were isolated from the amylopectins and it was found that clusters of Hylon V and VII had intermediate structures between normal maize and Hylon VIII. Hylon VIII amylopectin contained the longest inter-cluster chain segment (IC-CS) compared to Hylon V and VII. Also, Hylon VIII cluster had the longest inter-block chain segment (IB-CS) with less branched structure of building blocks; while normal maize cluster had the shortest IB-CS and most branched structure of building blocks. Furthermore, structural analysis of intermediate materials revealed a molecular structure between amylose and amylopectin. The internal chain segment profiles of intermediate materials from all samples were similar with mostly long and intermediate-sized chain segments. Amylose fraction from all samples contained mainly LMW molecules. The internal chain segments of amylose from all samples were mainly intermediate length.
Date: 2015-01
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