A Method for Estimating the Nature and Relative Proportions of Amorphous, Single, and Double-Helical Components in Starch Granules by 13C CP/MAS NMR

Applications of high-resolution solid-state NMR spectroscopy in food science

The principal applications of high-resolution solid-state NMR spectroscopy, in the field of food science, are reviewed, after a short general introduction, mainly focusing on the potential of these investigations, which are, today, routine tools for resolving technological problems. Selected examples of the applications in the field of food science of high-resolution solid-state NMR spectroscopy both in (13)C and in (1)H NMR particularly illustrative of the results obtainable are reported in some detail.

A novel approach for calculating starch crystallinity and its correlation with double helix content: a combined XRD and NMR study

A peak fitting procedure has been implemented for calculating crystallinity in granular starches. This methodology, widely used for synthetic polymers, is proposed to better reflect the crystalline content of starches than the method normally used, in which it is assumed that relatively perfect crystalline domains are interspersed with amorphous regions. The new approach takes into account irregularities in crystals that are expected to exist in semicrystalline materials. Therefore, instead of assuming that the amorphous background extends up to the base of diffraction peaks, the whole X-ray diffraction (XRD) profile is fitted to an amorphous halo and several discrete crystalline diffraction peaks. The crystallinity values obtained from the XRD patterns of a wide range of native starches using this fitting technique are very similar to the double helix contents as measured by (13)C solid state NMR, suggesting that double helices in granular starches are present within irregular crystals. This contrasts with previous descriptions of crystalline and noncrystalline double helices that were based on the analysis of XRD profiles as perfect crystals interspersed in a noncrystalline background. Furthermore, with this fitting methodology it is possible to calculate the contribution from the different crystal polymorphs of starch to the total crystallinity.

Effects of starch synthase IIa gene dosage on grain, protein and starch in endosperm of wheat

Starch synthases (SS) are responsible for elongating the alpha-1,4 glucan chains of starch. A doubled haploid population was generated by crossing a line of wheat, which lacks functional ssIIa genes on each genome (abd), and an Australian wheat cultivar, Sunco, with wild type ssIIa alleles on each genome (ABD). Evidence has been presented previously indicating that the SGP-1 (starch granule protein-1) proteins present in the starch granule in wheat are products of the ssIIa genes. Analysis of 100 progeny lines demonstrated co-segregation of the ssIIa alleles from the three genomes with the SGP-1 proteins, providing further evidence that the SGP-1 proteins are the products of the ssIIa genes. From the progeny lines, 40 doubled haploid lines representing the eight possible genotypes for SSIIa (ABD, aBD, AbD, ABd, abD, aBd, Abd, abd) were characterized for their grain weight, protein content, total starch content and starch properties. For some properties (chain length distribution, pasting properties, swelling power, and gelatinization properties), a progressive change was observed across the four classes of genotypes (wild type, single nulls, double nulls and triple nulls). However, for other grain properties (seed weight and protein content) and starch properties (total starch content, granule morphology and crystallinity, granule size distribution, amylose content, amylose-lipid dissociation properties), a statistically significant change only occurred for the triple nulls, indicating that all three genes had to be missing or inactive for a change to occur. These results illustrate the importance of SSIIa in controlling grain and starch properties and the importance of amylopectin fine structure in controlling starch granule properties in wheat.