Differential scanning calorimetry of raw and annealed starch isolated from normal and mutant maize genotypes
1987
Krueger, B.R. | Walker, C.E. | Knutson, C.A. | Inglett, G.E.
Analysis of the endosperm of the normal wild-type variety W64A-N (N) and 4 mutants in the W64A-N background revealed that the mutant shrunken (sh) had the smallest amount of endosperm starch and sh, waxy (wx) and amylose-extender (ae) had lower amounts of endosperm starch, while opaque 2 (o2) had higher amounts, than did N. Raw starch and annealed starch (raw starch subjected to heating at 50°C in the presence of excess water) of all 5 genotypes was subjected to differential scanning calorimetry (DSC). The DSC thermograms and the values of parameters of the thermograms are presented in graphical and tabular form, respectively, for all 5 genotypes. It is concluded from these data that variation in response to annealing reflected either the degree of restraint imposed during kernel growth and maturation, as in the case of o2 starch, or compositional differences within the starches, as in the case of the wx and ae starches. In the absence of amylose in the starch granule, as in wx, near-maximum crystallinity occurred as revealed by DSC data. As amylose content of the granule increased (to 29.9% in N and 60.4% in ae), an increase was detected in the amorphous phase and the degree of crystalline ordering diminished. Annealing increased this ordering, so that N starch had endotherms equivalent to those of wx starch. The extent of the changes brought about by annealing to the starches of all genotypes was inversely proportional to the degree of crystallinity of their raw starch.
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