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Structure-function characterization of unique starches from developmental lines. Y. JI (1), K.
Seetharaman (1), S. Duvick (2), L. M. Pollak (2), J. Jane (1), and P. J. White (1). (1) Iowa State University,
Department of Food Science and Human Nutrition, Ames, IA 50011; (2) USDA-ARS, Ames, IA 50011.
Starches were screened for unusual thermal properties from exotic lines
that are a part of the Germplasm Enhancement of Maize Program to develop breeding materials using useful
exotic germplasm. Thermal properties were determined using Differential Scanning Calorimetry on 20
individual kernels per ear of corn. Based on these screenings several lines with unusual thermal properties
were identified and used for further characterization. The objective of this study was to establish the
structure-function relationships that would explain the unique thermal behavior of these starches. Of the
physical attributes, only starch granule size distribution showed significant differences compared to normal
starch (Mo17). The unique starches with low gelatinization onset temperatures (T(oG)) had a higher
average granule size and a greater proportion of larger granules than normal starch. A qualitative measure
of the degree of crystallinity based on X-ray crystallography showed no differences between starch samples.
No significant differences were observed in the levels of amylose, amylopectin or their molecular weight
distributions, as measured by gel permeation chromatography; however, starches with the lower T(oG) had
a lower proportion of chains with DP greater than 16 and a lower proportion of branch chains below DP 13
when compared to normal starch, as measured by Pulsed Amperometric Detection. These studies help in
understanding structure-function relationships of starches to identify corn lines of interest for commercial
breeding.
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