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Cereal Chem 67:594-602   |  VIEW ARTICLE

Thermal Behavior During Gelatinization and Amylopectin Fine Structure for Selected Maize Genotypes as Expressed in Four Inbred Lines.

E. B. Sanders, D. B. Thompson, and C. D. Boyer. Copyright 1990 by the American Association of Cereal Chemists, Inc. 

To evaluate the effect of mutant genotype on starch gelatinization behavior, a series of starches in the Ia5125 inbred line was studied by differential scanning calorimetry (DSC). To examine the effect of amylopectin structure on gelatinization behavior, those maize samples containing the wx gene were also studied by size exclusion high-performance liquid chromatography (HPLC) after isoamylase debranching. Thermal analysis of starch gelatinization by DSC and the pattern of debranched chains by HPLC were then observed for four mutant genotypes (wx, ae wx, du wx, and ae du wx) from four inbred lines (Ia5125, Ia453, S3-61, and W64A). Within a line the DSC maximum temperature (Tmax) for the ae wx genotype ranged from 5.1 to 14.3 C above that for the genotype with the next highest Tmax. Enthalpy was highest for the ae wx starches in the S3-61 and W64A lines. The generally bimodal HPLC chromatograms had a greater proportion of the total area in the high molecular weight peak for the ae wx starches. Furthermore, the higher molecular weight shoulder of the low molecular weight peak became the dominant low molecular weight peak for the ae wx starches from the S3-61 and W64A lines. Either or both of these differences in amylopectin fine structure could explain the different thermal behavior of the ae wx starches during gelatinization. It appears that variation in the proportion of chains between and within the two major peaks, rather than displacement of the entire chain length distribution, may be responsible for variation in amylopectin structure. Variation in these proportions may help explain differences in physical properties of the starches.

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